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billr 11-30-2021 01:46 PM

Re: specifics on compression testing, P0301
 
The VB is same for both SOHC and DOHC.

fdryer 11-30-2021 02:13 PM

Re: specifics on compression testing, P0301
 
P0733 is a SES error code, not wrench error code. As mentioned previously, unless you have a better code reader programmed to read every GM code (P, U, B, C types) like GMs Tech-2 or an aftermarket scantool like VCX NANO, you're decoding generic P type codes. In this case, the error points to possibly something as simple as low xmission fluid when 3rd gear isn't detected at the right time in upshifts. The loss of xmission fluid should be the hint of this error code. Topping off xmission fluid should help reset the service engine soon/check engine light on its own without manual reset.

lanxer57 11-30-2021 07:01 PM

Re: specifics on compression testing, P0301
 
After I tested it last night, I also checked the transmission fluid dipstick, and it looked like the level was directly in the center of the cross-hash area, despite a very slow drip. It probably was service engine soon, but I did not look very closely, and never noticed how similar they look at a glance. Both yellow, contain the word "service", and are right next to each other. I was more concerned about the difference between years, because they are both SOCH.

lanxer57 11-30-2021 07:54 PM

Re: specifics on compression testing, P0301
 
I just took it out again, and it still says 3rd gear ratio is incorrect, but also says it is running rich (P0172), and it is the service engine soon light

TomM96 11-30-2021 08:33 PM

Re: specifics on compression testing, P0301
 
When troubleshooting, it is advantageous to proceed carefully, generally
addressing One issue at a time; it can be helpful to write down a record
of symptoms observed, and tests, or corrective interventions attempted.

TAAT ATF level is tested with vehicle at full operating temperature,
at idle, in neutral or park on flat surface; check both sides of the dipstick.

billr 11-30-2021 09:03 PM

Re: specifics on compression testing, P0301
 
After about '93 the VBs are all the same.

lanxer57 12-03-2021 01:02 AM

Re: specifics on compression testing, P0301
 
I forgot to mention that I sometimes have to shift it in and out of park before it will crank, because I have become so used to it that I barely notice. I suspect that this problem is likely caused by a problem with the neutral safety switch. Could this also be contributing to an incorrect 3rd gear ratio?

1996SL11.9L 12-03-2021 10:21 AM

Re: specifics on compression testing, P0301
 
That incorrect ratio code means that third gear is slipping or non existent.

When it commands 3rd gear it expects to see a certain correlation between input rpm and output rpm/mph.

lanxer57 12-03-2021 03:12 PM

Re: specifics on compression testing, P0301
 
I did not feel like it was slipping or non-existant (as if in neutral?) at any time that I drove it, just shifted a little bit hard a few when accelerating. It was not accelerating or shifting when the SES light came back.

lanxer57 12-04-2021 08:37 PM

Re: specifics on compression testing, P0301
 
This was the live data taken idling in park at about 750 RPM, IAT was about 60F, and coolant was 207F
STFT was between -33 and -36
LTFT was -17.2 (Are these good values?)
MAP sensor was reading 9 inches of mercury, a vacume guage had read 34 inches of mercury previously in the same hole (is the sensor bad?)
O2 sensor 1 reading fluctuates between about 0.35V, and 0.75V
O2 sensor 2 reading fluctuates between about 0.28V, and 0.68V (are the sensors bad? What do good readings look like?)
spark ADV was between 16 and 20 (Does this matter?)
TPS was 0%, I was not touching the throttle
O2 sensor readings are listed again for some reason, with the same values, except they are positive
STFT was listed again as sensor 2, 99.2% (Does that represent the amount of air, or fuel?)
That is all the live data my obd2 reader can read that is relevent (unless you want to know that it has fuel, or something)
The fuel pressure test result was earlier in the thread.

billr 12-04-2021 09:12 PM

Re: specifics on compression testing, P0301
 
STFT was between -33 and -36
[COLOR="red"]I can't really say whether this is good without knowing what the units are. If that is "-33" as a raw value ranging from -127 to +127 (a common 8-bit range), it OK. If, however, it is -33% of theoretical fuel required, it is a significant rim, something to be investigated, but still not a definite problem.[/COLOR]
LTFT was -17.2 (Are these good values?)
[COLOR="red"]Same problem here, units unknown. However, if this is percentage, it is probably too much.[/COLOR]
MAP sensor was reading 9 inches of mercury, a vacume guage had read 34 inches of mercury previously in the same hole (is the sensor bad?)
[COLOR="red"]9" Hg is pretty normal, about equal to 21" Hg on a vacuum gauge. Since no vacuum much past 30" Hg is even possible, I question the gauge. In fact, I wonder why they even bother with numbers beyond 30" on the dial...[/COLOR]
O2 sensor 1 reading fluctuates between about 0.35V, and 0.75V
[COLOR="Red"]That range is normal, but we need to know the rate; and you need to correlate the sensor reading changes to STFT[/COLOR]
O2 sensor 2 reading fluctuates between about 0.28V, and 0.68V (are the sensors bad? What do good readings look like?)
[COLOR="red"]Same comment[/COLOR]
spark ADV was between 16 and 20 (Does this matter?)
[COLOR="red"]Spark advance certainly matters. but that range and variation seems about right for idle[/COLOR]
TPS was 0%, I was not touching the throttle
O2 sensor readings are listed again for some reason, with the same values, except they are positive
STFT was listed again as sensor 2, 99.2% (Does that represent the amount of air, or fuel?)[COLOR="Red"]That would be fuel, a percentage of theoretical fuel required for the current engine running conditions (rpm, MAP, CLT, IAT[/COLOR]

What specific problems are you trying to solve now? A recap or update, please, it has been a long thread.

TomM96 12-07-2021 06:52 PM

Re: specifics on compression testing, P0301
 
> The turn signal switch also seems to only work intermittently.

On some vehicles that can be caused by poor connections, as from
bulb-to-socket ... or socket/harness-to-ground.

TomM96 12-07-2021 07:08 PM

Re: specifics on compression testing, P0301
 
> I sometimes have to shift it in and out of park before it will crank, because I have become so used to it that I barely notice. I suspect that this problem is likely caused by a problem with the neutral safety switch.

Very interesting. On my '97DOHC with TAAT, there was a problem of
an "unexplained SES". The one-time Satty dealer (now Mitsubishi) looked
at it for a couple hours ... and thought there might be an issue in the
instrument panel. I then drove a couple hours to a junkyard to get an InPnl.
The used InPnl was itself useless, but I noticed en route, that the SES
extinguished at about the 1-1/2 hour driving time. That became a persistent pattern, and convinced me that the PRNDL/Neutral-Safety SW took 1-1/2 hr
driving to Dry out moisture/salt within. So I procured a new switch from
Standard Motor Products ... which I mis-placed until after i lost possession of the car.
That car never had proper/acceptable starter-motor behavior, although
renewal of the Ig Sw improved it somewhat ... with which I also suspected the PRNDL/Neutral-Safety SW of involvement.

lanxer57 12-15-2021 04:11 PM

Re: specifics on compression testing, P0301
 
When I tightened the input shaft nut, I stuck a screwdriver inside it to hold it in place, the hole was slightly elongated. Could this cause a P0733?

lanxer57 12-15-2021 04:19 PM

Re: specifics on compression testing, P0301
 
I am trying to solve P0733, and P0172. The automatic transmission is also leaking a very slow drip. If I solve these problems, I expect more to appear.

billr 12-15-2021 04:22 PM

Re: specifics on compression testing, P0301
 
I doubt it. The ISN holds the 1st gear clutch; the clutch for 3rd is much deeper in the trans.

billr 12-15-2021 04:31 PM

Re: specifics on compression testing, P0301
 
[I][B]"When I tightened the input shaft nut, I stuck a screwdriver inside it to hold it in place, the hole was slightly elongated."[/B][/I]

I don't think it matters, but that statement above has me confused. The only hole I know of in the ISN is the threaded one in the ID. I don't see any possible way to use a screwdriver in that hole to hold things while tightening the ISN. Did you mean a hole in the [I]clutch drum?[/I]

lanxer57 12-15-2021 06:07 PM

Re: specifics on compression testing, P0301
 
Yes, the one in the side of the "clutch drum".

lanxer57 12-28-2021 02:49 PM

Re: specifics on compression testing, P0301
 
could the codes P0172, and P0733 have anything to do with the fuel that sat in it for at least 6 months, and needed fuel stabilizer to run at all?

billr 12-28-2021 04:43 PM

Re: specifics on compression testing, P0301
 
No on the P0733; that is strictly a trans issue.

Maybe on the P0172, but I kind of doubt it. I have let fuel sit for far longer than 6 months with no apparent problems. Carbs, EFI, diesel; none of them seem especially sensitive to that "old fuel" bogeyman.

lanxer57 12-28-2021 10:06 PM

Re: specifics on compression testing, P0301
 
could it be the ECTS that I replaced a few months, and less than 10 miles ago? Are they often defective when brand new? (it is brass, shows up on the guage, and on the obd2 reader)
could it be an oxygen sensor? (those show voltage on obd2 as well)
Is there a list of possible causes for it to run rich but dad not to smell it?
What about an incorrect gear ratio that feels normal while driving? (at speeds not greater than 30mph)

billr 12-29-2021 12:43 AM

Re: specifics on compression testing, P0301
 
Do you have live-data that shows ECT? If live-data as 190F or more when the engine is hot, then ECT is not the cause of rich running.

There are many reasons why the engine could be (detected as) running rich. Here are some common ones:

"Intake blocked, EVAP canister purge valve, fuel pressure, EGR system, injector(s), HO2S"

I'm not sure what your question is regarding the P0733. That indicates a trans problem, and it seems you are saying the car will not operate normally over 30 mph. Why does that puzzle you that a car with a bad trans has trouble going over 30? Does your live-data show "Trans Turbine Speed? That can be compared to "Vehicle Speed", in 3rd (or any) gear to verify something is slipping and the P0733 is valid.

lanxer57 12-29-2021 04:07 AM

Re: specifics on compression testing, P0301
 
The ECT is above 190 when warm. The reason I am not driving faster than 30mph is because I am only driving on small residential streets, and do not want to get pulled over. This vehicle can not pass an emissions test, meaning it can not get registered. If it gets pulled over, it will get impounded, and I do not have the money to get it out of an impound. This cowardice has nothing to do with the capabilities of my car, it could go faster, I am simply reluctant to take more risks.

fdryer 12-29-2021 11:47 AM

Re: specifics on compression testing, P0301
 
Can you post intake air temperature, coolant temperature and map sensor value on a cold engine, ignition on (engine off) and outside temps? IAT and coolant sensor should be the same or close to outside temperatures. Map sensor should be the same as local barometric pressure from weather sites (currently 29.87 in hg@7:30 am today in Aurora). These are baseline values to help verify sensors are operating before an engine start. On startup, a cold engine coolant sensor should be showing rising coolant temps until reaching thermostat operating temps then remain within 5-10 degrees of t-stat rating. Your coolant sensor is fine from posted data. The t-stat is fine since it's within operating range of its rating. The intake air temperature is known to be reliable but if it fails, it can contribute to P0172 so checking its output at cold engine/ambient temp/before starting compares its output to outside air temps. Plus or minus a few degrees is fine. Intake air temps will vary from airflow at speed, stopped when engine heat flows towards it, etc. The coolant sensor does the same, data for the pcm to vary fuel mixtures. The map sensor is basically the engine load sensor measuring manifold vacuum as throttle opening and engine rpm vary as data for the pcm to vary fuel mixtures on a larger scale compared to iat and coolant sensors. The exhaust manifold O2 sensor measures oxygen leftover from combustion as data to the pcm to quickly alter fuel mixtures several times per second to regulate air/fuel mixtures as close to 14.7:1 for tight emissions control. This upstream sensor fluctuates quickly between 0.3v-0.7v but switches too quickly for digital millimeters to see unless a quick acting bar meter is seen. An oscilloscope for geeks shows the speed of O2 sensor cycling rates. A worn out, slow cycling O2 sensor can alter fuel mixtures to either lean or rich conditions.

billr 12-29-2021 02:13 PM

Re: specifics on compression testing, P0301
 
OK, I understand that operation over 30 is simply unknown, not necessarily "bad". Do you hold it in lower gears manually sometimes and accelerate fast (or up steep hills), so the engine is seeing some operation at higher rpm and load? Regardless, let's ignore the P0733 until you can take this beast up to highway speeds routinely. Will the trans code prevent it from passing emissions test?

If (live-data) temp on the engine warmed-up is 190F, that is good enough that the ECT can also be ignored regarding the P0172.

So, that leaves you back to that list I quoted a few replies ago. There are other possibilities too, I sure, but start with those.

lanxer57 12-29-2021 07:37 PM

Re: specifics on compression testing, P0301
 
I may inspect the components listed tomorrow.
The websites that describe colorado emissions testing requirements/criteria are not very clear on what exactly will cause a vehicle to fail a test.
"A check engine light on a vehicle at least 12 years old may still pass if the I/M 240 test can be run and the car can pass the test."
It does not appear to list anywhere what the criteria for these 4 minute dynamometer tests are.
It also mentions that smoke beyond 5% opacity will cause it to fail, as well as any "obvious fluid leaks, worn tires, etc". I do not know how obvious these fluid leaks would need to be, the trans is leaking enough to leave a spot on the driveway, but not enough to see it dripping. It also mentions a visual inspection, but does not say weather they look at horns, or turn signals (which are not currently working).
It does not mention anything about coolant lights, but the do flash when sitting in the driveway.
It also says that "Catalytic Converter, Oxygen Sensor, and Heated Oxygen Sensor (if so equipped) monitors set to “Ready” during the inspection. Vehicles model year 2000 and older can have two remaining monitors “Not Ready”". I do not remember ever seeing these symbols turn green on the obd2 reader, and they are definitely not ready now.

lanxer57 12-30-2021 12:00 AM

Re: specifics on compression testing, P0301
 
Should I just try to take an emissions test, just to see how it goes?:stoplight
maybe take one every month, just in case? I think that is what they want us to do... it is only 25$ per test. (unless it gets impounded):arr:

fdryer 12-30-2021 12:48 PM

Re: specifics on compression testing, P0301
 
Prior to 1991, on board diagnostics (OBD I or OBD II) didn't exist. Every vehicle manufacturer did their own thing as EFI systems became complicated then tighter emissions controls added to EFI complications. My Mercury Sable wagon was required to run on emissions inspection rollers as the inspector varied drive wheel speeds following a screen displaying a programmed road drive to create loads and speeds with an exhaust pipe analyzer sniffing the exhaust. This was testing the emissions system as speed and loads changed. After this program ended, a report was generated for pass or fail. 1991 vehicles became the first to utilize emissions self tests incorporated into engine computers to eliminate inspection stations having one dedicated service bay for emissions inspections. Every vehicle made for the USA market since '91 performs emissions self tests on every engine startup with constant monitoring while driving. In effect, as long as the check engine/service engine soon/malfunction indicator light remains OFF, a vehicle has passed emissions self tests before driving into a state inspection station.

Your '99 uses OBDII because '96+ vehicles incorporated tighter emissions control programs. It's still on board emissions self testing. This means no rollers or exhaust sniffing analyzers (outdated). Your reader or scantool, if it displays emissions monitors in READY or NOT READY status is all that's needed to tell you long before visiting a state emissions inspection station whether or not your vehicle passes its on board emissions self tests or not with details on which monitors failed for you or mechanic to address. You have options. Either continue here and try understanding your situation with the two error codes and any not ready monitors and make repairs or search for a mobile mechanic with expertise in EFI systems, experience in diagnosing and troubleshooting error codes or ask a friend who's experienced in these matters. Expertise in repair shops are hit or miss.

fetchitfido 12-30-2021 01:11 PM

Re: specifics on compression testing, P0301
 
The OBD-II emissions 'ready monitors' require a completed drive cycle , which itself requires something the OP is unable to do ([URL="http://obdii.com/drivecycle.html"]DC explained[/URL]). Until a drive cycle can be completed it'll never pass an OBD-II scan based emission's test.

fdryer 12-30-2021 02:38 PM

Re: specifics on compression testing, P0301
 
I'm aware of his predicament.

lanxer57 12-30-2021 03:20 PM

Re: specifics on compression testing, P0301
 
Is there any leagal way to complete a drive cycle in an unregistered vehicle? What about a time and place where the police would be least likely to notice?

billr 12-30-2021 03:47 PM

Re: specifics on compression testing, P0301
 
Between 3AM and 5AM you can do pretty much anything you want; especially on a Sunday morning.

However, I think you are overly concerned about this. I have driven a wide variety of "illegal" vehicles on the roadways over my many years (not to mention driving in an illegal manner!). It just isn't that hard to keep from being noticed by police. An expired registration? I don't think they would ever stop you for just that alone.

lanxer57 12-30-2021 04:41 PM

Re: specifics on compression testing, P0301
 
I only have one licence plate, salvaged from the saturn (and mustang) that I crashed (the other one probably fell off the tow truck). I bought this one from a field with no plates on it, likely having been put on one of the other cars in that field. It had been sitting there for at least 6 months, likely more.

lanxer57 12-30-2021 07:35 PM

Re: specifics on compression testing, P0301
 
I have 2 EGR valves. One off the 2001 SOCH engine that rattles when turned upside down. A/E;0, B/C; 1.25-4.9Kohm, B/D; 4.63Kohm, C/D;4.65-0.6Kohm
The other is off the 1999, and does not rattle as much. The ohm readings were:A/E;0, B/C;1-4Kohm, B/D;4Kohm, C/D;4.25-1Kohm
results are in this order: Left alone-Pushed in. Any not mentioned were O.L. I briefly soaked them both in carb cleaner. Are they supposed to rattle inside the cylindrical part?

lanxer57 12-30-2021 08:17 PM

Re: specifics on compression testing, P0301
 
The intake is not blocked, unless you count the plastic box that connects to the filter box that leads nowhere. the fuel pressure was within specs the last I checked, the fuel injectors did leak slowly with the engine off, but seemed to fix the misfire. I ran out of daylight (and my hands went numb) before I could remove the EVAP canister valve. I hate cold weather. How would I test an oxygen sensor? Is there more to the EGR system than just the valve?

billr 12-31-2021 02:40 PM

Re: specifics on compression testing, P0301
 
How about the air filter itself, is it relatively clean-looking? Have you looked through all the plastic ducting to be sure there is no blockage? Regardless, a "blocked intake" is unlikely the cause.

Have you taken fuel pressure readings while driving, watched how FP behaves over more than a few seconds and at various engine operating points? does this year have the fuel-pressure-regulator in the filter? I think those are not "vacuum-referenced" FPRs, so much easier to check; but I also think they are failure-prone, and only a few replacement brands seem to be reliable. I have only gen1 cars, so have no experience on this. Hopefully others will speak up.

Are you suspecting leaking injectors because FP decays quickly when the engine is not running? That is a good clue, but hardly definitive. The FP can drop like a stone from a bad check-valve in the pump/FPR and have no real significance, as long as the injectors don't leak and the pump can develop proper pressure while running. However, [I]any[/I] hint of leaking injectors has to be investigated, you have to remove the injectors and test them. While out, I would check them for flow-rate and pattern, too. This is probably easiest and best done by sending them to a shop for cleaning/testing.

The O2 sensor can be tested somewhat, but if the reading is moving above and below 450mV (as seen in live-data) every second or so, then it is probably OK. You need to watch that reading along with the STFT to see if they correlate.

Yes, there is far more to the EGR system than just the valve (wiring, PCM, gaskets, ducting); but the valve itself [I]is[/I] the prime suspect there. I suggest blocking the EGR valve ports with a "solid gasket" made from thin steel; see how that changes the engine codes set.

fdryer 12-31-2021 05:12 PM

Re: specifics on compression testing, P0301
 
[QUOTE=lanxer57;2368625]Is there any leagal way to complete a drive cycle in an unregistered vehicle? What about a time and place where the police would be least likely to notice?[/QUOTE]

When an error code pops up, the on board emissions self tests (normally running the entire time the vehicle is running) halt at the last emissions monitor.[B][I] Emissions self tests will not proceed until the error is corrected. This applies whether or not resetting the error occurs.[/I][/B] I do not know if there's a specific sequence when each monitor is tested but be aware that a drive cycle is useless at this point as it will not complete until the error is fixed. And resetting the error code does nothing if the error reappears while all the memorized emissions parameters are erased, forcing this car to start a drive cycle as if the vehicle just left factory assembly. Presuming P0172 is a hard error, meaning it won't go away after resetting the system, all you're doing is driving around with some monitors going to ready status but halting at the error code, effectively putting the vehicle in the same place you started from the beginning of this thread. A drive cycle will not correct a hard error, in this case P0172. What you're hoping for is a 'hail Mary' fix and it won't happen with a drive cycle.

A drive cycle works only for a vehicle[I] without error codes[/I] like a simple loose gas cap error code with someone resetting the error (resetting all emissions parameters) then driving for a few days as the OBD II system performs its emissions self tests, all switching from not ready to ready status without the driver seeing anything in everyday driving with the check engine light remaining off. This best case scenario occurs because the engine already met all emissions parameters but the loose gas cap triggered the evap leak error code. Simply tightening the gas cap several clicks without resetting the system would allow the system to detect the evap system operating without a leak, reset the check engine light and continue where it halted to allow a full ready status. With a ready status displayed on a reader an immediate inspection will pass if it was required.

Resetting the error code erases all memorized parameters and requires the drive cycle to relearn them again, provided zero error codes occurs. P0172 is preventing the emissions self tests from completing any attempt of a drive cycle.

lanxer57 12-31-2021 08:25 PM

Re: specifics on compression testing, P0301
 
Yes, a drive cycle would be useless now, but will need to be completed if I ever fix all of the error codes. The computor resets every time the battery is disconnected. This has happened several times, and will probably need to happen again. Will the transmission 3rd gear ratio code P0733 also interfere with a drive cycle? If that is the case, than it will also need to be solved before any emissions test. Yes, the air filter is clean, but the filter box, and intake were salvaged from the 2001, because the original was damaged. I do not believe that would make a difference, but the holes the mounting bolts go into do not line up perfectly. Is the cylindrical part of the EGR valve supposed to rattle when shaken, or turned upside down? With key on, engine off, without having been cranked,pressure started at 42 PSI, dropping to 38 PSI after about 5 minutes. Is this a hint that injectors are leaking? Fuel pressure at idle bounced around for a few minutes, before settling at 47psi. It is already in a different place from when this thread started, the misfire has not come back yet, and I did complete a compression test.

fdryer 12-31-2021 09:15 PM

Re: specifics on compression testing, P0301
 
Unfortunately, you're in the proverbial rock and a hard place with two error codes that won't go away until each one is addressed with a repair. It's a waste of time with repeated resets since each reset requires the drive cycle and if you try any emissions inspection, your car fails based on what you have (P0172 and P0733). It's your money if you try an inspection as the inspector is obligated to issue a report whether pass or fail. If more detailed info is listed, better for you but according to this thread the two outstanding and repeating errors will not allow any drive cycle to complete. All monitors must go from not ready as a drive cycle begins until each monitor switches to READY status as the drive cycle progresses to its completion, barring any error code.

Search for egr description and operation. [url]https://www.aa1car.com/[/url] is one site with detailed info on EFI sensors. Inside an electric egr valve is a stepper motor controlling pintle valve movement as commanded by the pcm. It's closed at idle or wide open throttle, varying exhaust gas flow into the intake manifold in various throttle positions. Nothing should rattle but more importantly, zero egr valve error codes from a good one (rattles or not). I would be more concerned of egr error codes than one rattling when shaken.

Fuel pressure bleed off right after turning ignition on, engine not started, should remain steady for at least a few minutes then start bleeding down. Nothing is perfect so a small bleed down may be ok. Several ways to check for injector leaks; removing injectors, reconnecting them back to the fuel rail and electrical connections, laid out over the engine and turning on ignition to see if any leak or removing spark plugs and exclaiming each one for signs of excess fuel burning (not an exact science but can help). A third method using a borescope inserted into a cylinder then cycling ignition on to observe for fuel spraying/leaking out each injector. Performed for each cylinder. As soon as the fuel pump runs to pressurize the fuel rail, every injector has full pressure. Any leak should be seen with a borescope.

billr 12-31-2021 11:28 PM

Re: specifics on compression testing, P0301
 
These EGR valves do [I]not[/I] use a stepper. The pintle is positioned by a "voice coil" solenoid. I don't know whether the electric drive is PWM or true analog DC current; but that doesn't really matter.

That solenoid plunger is spring-biased and should not just clunk round easily, but it[I] may[/I] make a rattle if you shake it violently enough. Just turning it over? No, I would not expect it to rattle just turning it upside-down.

fdryer 01-01-2022 12:26 PM

Re: specifics on compression testing, P0301
 
From [url]https://www.aa1car.com/[/url], there are various egr valves in use since 1973. They are ported egr valves operating on intake manifold vacuum, positive backpressure egr valves, negative backpressure egr valves, pulse width modulated egr valves, digital electronic egr valves and linear electronic egr valves. Engines with variable valve timing eliminated egr valves altogether.

I'm pretty sure the S-series uses linear electronic egr valves with stepper motors.

billr 01-01-2022 02:44 PM

Re: specifics on compression testing, P0301
 
They are called "linear", and certainly operate in an analog/proportional mode, but they are not steppers.

Want a sanity check? Count the electrical connector pins/wires, there are only five: three for the feed-back potentiometer and two for the driving coil. A stepper would require a minimum of four (floating) wires, which added to the three for the pot would make the minimum pin-count seven...

fdryer 01-01-2022 03:36 PM

Re: specifics on compression testing, P0301
 
I won't debate with you. My guess is you haven't read descriptions from the link as a source of factual information.

billr 01-01-2022 04:13 PM

Re: specifics on compression testing, P0301
 
Oh, I looked at the link. I'm not saying that GM hasn't used an EGR with stepper; I'm only insisting the '94-99 Saturn S-series EGR doesn't have a stepper.

But yeah, let's drop it. Anybody reading should be aware by now that there is some confusion about the EGR valve, and should investigate personally if it matters to them.

lanxer57 01-07-2022 07:53 PM

Re: specifics on compression testing, P0301
 
I cleaned the EGR, and the purge valve is definitely working. I tried to start it a few days ago, and it shook violently as if it was about to explode. I started it today, and it ran fine. P0172 and P0733 are still there, but a new code called P0340 just showed up. STFT was about -40%, LTFT was -17%.

billr 01-07-2022 08:44 PM

Re: specifics on compression testing, P0301
 
The P0340 is usually because the spark-plug wires are not routed properly. Post a picture of how you have them so we can do a visual inspection.

Have you tried blocking of the EGR ports with a solid steel "gasket"?

lanxer57 01-08-2022 03:39 AM

Re: specifics on compression testing, P0301
 
What exactly would I use to block the EGR? soda cans are not steel, and soup cans are not flat. I had the spark plug wires routed in a way that could be represented by this text based image:

1234(plugs)
! ! ! !
4123(coils)
Front of saturn

Is this the wrong order? Could I have not pushed the boots hard enough to connect properly? Could it be something else? The code reader said it was the cam sensor.

billr 01-08-2022 03:43 PM

Re: specifics on compression testing, P0301
 
Use the end off of a steel can. I think you could get a gasket out of a 28oz can, but one of those big "gallon" ones for sure!

Are the #1 and 4 plug wires separated as much as possible as they go up to the plugs; with 2 and 3 in between them?

Note that there [I]is[/I] no cam sensor, per se, that CMP signal is synthesized by the ICM/PCM based on the #4 plug tower/wire.

lanxer57 01-08-2022 08:52 PM

Re: specifics on compression testing, P0301
 
1 Attachment(s)
This is an actual image of the spark plug wires in the order they have been in.

billr 01-08-2022 09:38 PM

Re: specifics on compression testing, P0301
 
That looks OK to me. You have marked in red where 1 and 4 are close, but that much is usual since the wires connect to the coil towers so close together. Also, "crossing" like that minimizes cross-talk problems; it is when wires run parallel for some distance that there is more concern.


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