Forums Forums (
-   S-Series Tech (
-   -   specifics on compression testing, P0301 (

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][/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][/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:

! ! ! !
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.

All times are GMT -4. The time now is 10:11 AM.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2022, vBulletin Solutions Inc. The Saturn Enthusiasts Site.