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lanxer57 11-17-2021 11:48 AM

Re: specifics on compression testing, P0301
I have replaced the spark plugs recently with NGK plugs, but they may have gone bad afterward, so I will see if the auto parts store has any. (they had to order some last time).
Dad also smelled it running rich, although I can not verify weather it still is because my nose does not work.
It is also almost out of fuel, so I will need to fill up a gas can.

Cheyne 11-17-2021 01:11 PM

Re: specifics on compression testing, P0301
What NGK plugs did you use?

alordofchaos 11-17-2021 03:28 PM

Re: specifics on compression testing, P0301
couple of coil vids (I have not watched)



Pull out your #1 plug and any other plug. Compare gaps, if the same, swap those two plugs. If you still get a P0301, you know the problem was not defective plug - if your misfire moves with the plug, you know it was defective.

Same with fuel injector, if you suspect that. Swap the #1 with one of the others, if the problem moves with the injector, bad part. I saw that you replaced the whole rail - it is unlikely, but possible, that a used rail also had problems with the #1 fuel injector. By switching the #1 with a known good injector, you've ruled that out.

[QUOTE]After removing all other spark plugs, and putting the battery on a trickle charger, it seems to be able to crank continuously most times. I released the pressure whenever it stopped before the needle did.[/QUOTE] Not sure i understand what that last sentences means. Are you getting 10 strokes on you recent test? Recharge the battery if needed between testing cylinders.

[QUOTE]The plug in cylinder 1 is black like coal, from excessive fuel [/QUOTE]could also be insufficient air (very unlikely) or weak spark with incomplete burning.

[QUOTE]The live data from the sensors mentioned seems to be working with the cheap OBD2 scanner.[/QUOTE] What do your IAT, ECTS, and MAP read, on a cold engine, and what is the ambient temp during that read?

billr 11-17-2021 03:59 PM

Re: specifics on compression testing, P0301
What are the compression readings now that you can crank continuous? All plugs out, throttle wide open, 5-10 strokes, no extra oil in cylinders. Warm or cold doesn't matter to me.

alordofchaos 11-17-2021 06:57 PM

Re: specifics on compression testing, P0301
^ ^ ^
Yeah, we;re still kinda guessing here because we don't have numbers we can be confident in
[QUOTE=lanxer57;2367471] Does that apply to any engine? Even fuel injected ones?[/QUOTE] Yes, the fuel supply doesn't matter. As a matter of fact, you should have pulled the PCM-B fuse out, as mentioned in the links I provided upthread. That shuts off the fuel injectors - which both prevents fuel from washing down the oil from the cylinder walls [I]and throwing off your compression reading [/I]- by temporarily sealing any leaks.

You are taking a fixed amount of air at ambient pressure in the cylinder, compressing it, and seeing the pressure after compressed. A low compression number means air is leaking out, either past compression rings or valves (damaged/worn valve or valve seat). At higher altitude, that same amount contains less air to compress.

[QUOTE=OldNuc]Nominal compression for a high mileage good condition DOHC is 190-220psi and[B] SOHC is 175-205[/B]psi.[/QUOTE]Using the 80% adjustment fetchhitfido provided, the SOHC range should be 140-164 psi. Or 149-174 if you use your 85%

[QUOTE]Do not screw it into the head past the point the sealing o-ring just contacts the head. Do not overtighten as it will leak.[/QUOTE]

lanxer57 11-18-2021 01:19 AM

Re: specifics on compression testing, P0301
The new spark plugs that I installed a few weeks ago are NGK, BKR4ESA-11 according to what is printed on the box.
The ones installed by a previous owner were autolite double platinum APP 3926, something I believe is specifically advised against for S series.
For my last test on reply #16, I removed all spark plugs, fully charged the battery, removed the PCM B fuse, and propped up the gauge on a large pair of channel locks in order to see the needle moving. The top row shows the results of that before adding oil, the bottom row shows results after squirting 1 TSP of oil in all of them with a syringe. For the tests with the oil added, the trickle charger stopped working (likely the faulty garage outlet), so I can not be sure if it was still fully charged.
I will need to conduct more tests on another day, I had other things today.

billr 11-18-2021 01:47 AM

Re: specifics on compression testing, P0301
I can't rely on your results of reply #16 until you answer my question of #17: was that cranking (for 16) continuous, not interrupted like before?

If the cranking [I]was[/I] continuous for each compression test, then it doesn't seem likely compression is the issue; although there may still be a problem with exhaust valves. Compression can be fine, even if exhaust valves are not opening. That is pretty rare, though, so let's get back to the easier (and more likely) stuff first.

Swap around the injectors and coils, and check plug gap. You can not assume plug gap (or anything else) is OK just because the plugs are new. Our modern retail policy of "anything is returnable" ensures nothing is sure to be [I]really[/I] new.

How about those plug wires? I would like to see the routing, but how about the condition? If they look at all old, I would replace them. It is pretty hard to tell if a plug wire is breaking down intermittently or only under certain operating conditions.

lanxer57 11-18-2021 02:48 PM

Re: specifics on compression testing, P0301
yes, I got it to crank continuously with all spark plugs removed, I released the pressure from he guage whenever it did stop before the needle did. The spark plug wires were replaced with the plugs, and should be brand new. I may be able to check plug gaps, and swap fuel injectors when I return home.

billr 11-18-2021 03:15 PM

Re: specifics on compression testing, P0301
Try swapping coils, too.

It seems, then, that your (dry) compression is in the 145-160 range on all cylinders Do we all agree that is OK for a SOHC at 5770' altitude?

alordofchaos 11-18-2021 10:35 PM

Re: specifics on compression testing, P0301
[QUOTE=billr;2367555] Do we all agree that is OK for a SOHC at 5770' altitude?[/QUOTE]
Yes, I agree with moving on - switching out [I]known good[/I] (not [I]new/different[/I]) parts.

[QUOTE]You can not assume . . . (or anything else) is OK just because the . . . are new.[/QUOTE] exactly. Installed a few new, out of the box, defective parts then pulled my hair out trying to troubleshoot because I assumed the new part was good. In this case, you are better off using known good parts for troubleshooting.

Autolite double platinum is actually OK for these cars (I did not check the specific number you listed for fitment in the SOHC). The double platinum are not fine-wire plugs - most platinum plugs are single plat / fine wire.

I ran double plats in my DOHC with no issues (no gain,either, so went back to coppers)

1996SL11.9L 11-20-2021 07:22 AM

Re: specifics on compression testing, P0301
I would start by replacing the spark plug in cylinder 1. If the missfire goes away and or the plug turns black again Iíd look at the fuel injector for that cylinder. It appears itís stuck open and running that cylinder rich or youíre burning major oil in that cylinder.

lanxer57 11-20-2021 08:13 PM

Re: specifics on compression testing, P0301
I have not yet had time to switch anything out, but I did do a test the fuel pressure.
With key on, engine off, it started a 42 PSI, dropping to 38 PSI after about 5 minutes. At idle, it bounced around for a few seconds before settling at 47 PSI.
I also tested vacuum at the valve cover to intake hose. it quickly reached 5 inches of mercury, before settling just below 10.

billr 11-20-2021 09:41 PM

Re: specifics on compression testing, P0301
I would prefer not to get into fuel-pressure, just yet; except to say I don't think it would affect only one cylinder. Let's pursue the coil/injector swapping first.

for you, is #1 cylinder the one on the passenger-side; where the serp belt is?

lanxer57 11-21-2021 09:07 PM

Re: specifics on compression testing, P0301
I checked the spark plug gap, they were all 0.040 inches. I cleaned them with a rag, and put them back in. I switched the misfiring cylinder 1 plug with the cylinder 2 plug. The "service" light did not come back on for at least half an hour of idling in park, and turning the engine off several times. it only came back on when I turned it off for 30 seconds to retrieve my license to drive it down the street and back. It did not explode, but it was not driving faster than 20 MPH or longer than 1 minute either.:stoplight When I selected a setting for OEM DTCs for saturn, I found 47 codes, many of them contradictory, with the label "did not complete SC" or something similar. Global OBD2 did not find any codes after 40 minutes:clock: of idling with "service" light on, so I do not know weather or not switching the spark plugs changed anything.

lanxer57 11-22-2021 01:41 AM

Re: specifics on compression testing, P0301
after driving up and down the street, half of the saturn specific codes vanished, but still no global OBD2 codes.

billr 11-22-2021 10:13 AM

Re: specifics on compression testing, P0301
Post what codes are set now.

Was the original problem [I]only[/I] that a P0301 was set, was the engine running OK?

PS: I do understand that the P0301 prevented you from passing smog test; an important problem in itself.

1996SL11.9L 11-22-2021 10:30 AM

Re: specifics on compression testing, P0301
Everytime my wrench light came on on my 96 it was to tell me the check engine light bulb was blown.

Your check engine light comes on at key on and goes off at engine run and no missfire codes?

lanxer57 11-22-2021 03:53 PM

Re: specifics on compression testing, P0301
The engine was running rough, with low pitch noises coming from exhaust. I always assumed that this was caused by the misfire that was detected by the OBD2 reader. These noises show up intermittently, and when present, get louder when moving the vehicle up and down the driveway. They were last heard the day before I changed the fuel injectors. I will try using another OBD2 reader to see if that is the problem, and watch for any light bulbs that may be out.

lanxer57 11-22-2021 09:21 PM

Re: specifics on compression testing, P0301
The lights that show up with with key on, engine off are "service engine soon", "service" wrench, battery, oil, low fuel, and parking brake. When started, all turn off except parking brake (I am on a sloped driveway), "service" wrench usually comes back after a minute or so. The low coolant lights flashes sometimes, but it is filed to the maximum cold level, and the resevoir was recently cleaned, so I think it is because of the sloped driveway. I tried a different OBD2 reader, this one does not have live data. It did not find any codes in "global" mode either. The status light is orange, flashing red icons for O2 sensor, catalytic converter, EVAP, and EGR. There are 27 error codes in OEM enhanced mode for saturn, some repeat multiple times, some appear to be contradictory. This is the order they appeared in: P1640, P1641, P1620, P1640, P1641, P1620, P1640, P1641, P1620, P0133, P0401, P0420, P0440, P0130, P1134, P1133, P1602, P1380, P0733, P0734, P0741, P0748, P1582, P1584, P0442, P1441, P0446

billr 11-22-2021 10:33 PM

Re: specifics on compression testing, P0301
But the original P0301 has not returned? Ugh! Does the car drive OK?

Whenever I see a long and eclectic list of codes like this I suspect the PCM, power/ground connections to the PCM, or the code reader.

Try a different code reader, take it to your FLAPS, if necessary, for a free read. Check the PCM 5V supply, easiest done at the MAP sensor or TP sensor or EGR valve. Check voltages at the PCM power and ground pins, back-probing and with the PCM fully powered up (KOEO).

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