95 SE misfire/vacuum leak/spark issue.. I cant tell - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-11-2010, 02:01 PM   #11
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Well I'm almost ready to turn my attention away from a vac leak. I would assume that if it were a vac leak, that it would be pretty much constant. What is happening to me seems completely random. Broken hoses and cracked fittings don't usually stop leaking then start again etc. I have had a vacuum issue in this car before, and from what I have experienced, this would have to be a pretty good leak, and a good leak I think would mean, to good to off and on seal up again.
There again, I am no expert. So if I need to be put in my place on this issue, please feel free to set me straight lol.
Id like to say it acts better when warm, but that'* not even always the case. This is the 1st time since it really acted up on Thursday that it seems to be OK again.
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Old 01-11-2010, 04:56 PM   #12
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Where is this IAC valve on the L27?
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Old 01-11-2010, 04:59 PM   #13
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No clue my friend. Seems I'm just learning about it myself. I don't even know if mine is alright. I probably know what it is, just not by a name . I bet I called it that next damn thing I had to put back on lol.
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Old 01-11-2010, 05:21 PM   #14
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IAC is in the picture...
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Old 01-11-2010, 05:36 PM   #15
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yea I remember that, cant remember what I called it though. Mine is plugged in and appears sound though.
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Old 01-11-2010, 11:34 PM   #16
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The car was doing it when I left work, Drove about 15kms, and did a few errands (2 stop and starts), and once I got back to my town, I stopped at my parents. All the way to town the car acted funny. After a 10 min jaunt down the highway it was running awesome when I left my parents. wth :(
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Old 01-12-2010, 05:57 PM   #17
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Your car can run this poorly and you haven't gotten a Check Engine Light?

Proceed with your checking, but i would suggest you invest in a scantool. Something like the Actron CP9145 with the OBDII cable. The '95 is a tweener year. You need a scantool which uses the OBDII connection cable, but reads and reports OBDI data and codes. The street price on the CP9145 is $150, but that is because it includes all of the different OBDI car company cables. There is only one cable for all companies in OBDII. I have seen the CP9145 go for $60-70 with just the OBDII cable on ebay.

And i hate to bring this up...

I'm on my third PCM with my "95. The '95s have the absolute worst PCM wackout rate, by far. It'* really odd that the PCM is not throwing a CEL and DTC code.
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Old 01-12-2010, 07:22 PM   #18
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I seen my check engine light only once, about 20 seconds before my engine blew up. I bought the car used, and didn't know about all the intake issues plaguing this motor. The car ran like a dream at 1st, and progressively got worse. Its a long crappy story, so I wont get into it now.
I have no CEL. Car feels like its missing, but its not steady, more of a kick here and there. When its feeling like acting up, accelerating on the highway causes shudders and little kicks also. It seems to go away after a good 20 minutes of driving.
I get a lot of RPM fluctuations while at rest, and in park it will even stall out. Always fires right back up like nothing happened.
Your correct that I don't have a scan tool for this car, despite owning 3 different ones. I wish I read up on this car, and the 95 OBD hybrid garbage, and I may have not purchased it. Although it has given me a lot of useful car info and skills I would not otherwise have.
I'm kind of stumped with this one for the moment, but I'm sure once I can get in the garage this weekend, I will be able to sort this out.
How do you tell if its the computer or not? Is there an easy way to determine this, or do you just have to get a new one, put it in, and cross your fingers?
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Old 01-12-2010, 08:53 PM   #19
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Quote:
Originally Posted by WeaD View Post
I seen my check engine light only once, about 20 seconds before my engine blew up. I bought the car used, and didn't know about all the intake issues plaguing this motor. The car ran like a dream at 1st, and progressively got worse. Its a long crappy story, so I wont get into it now.
I have no CEL. Car feels like its missing, but its not steady, more of a kick here and there. When its feeling like acting up, accelerating on the highway causes shudders and little kicks also. It seems to go away after a good 20 minutes of driving.
I get a lot of RPM fluctuations while at rest, and in park it will even stall out. Always fires right back up like nothing happened.
Your correct that I don't have a scan tool for this car, despite owning 3 different ones. I wish I read up on this car, and the 95 OBD hybrid garbage, and I may have not purchased it. Although it has given me a lot of useful car info and skills I would not otherwise have.
I'm kind of stumped with this one for the moment, but I'm sure once I can get in the garage this weekend, I will be able to sort this out.
How do you tell if its the computer or not? Is there an easy way to determine this, or do you just have to get a new one, put it in, and cross your fingers?
See, you are describing something which has to throw a code. It'* like the PCM is already in an error state.

The logic in the '95 is a throwback to the Series I. For example, If you have a problem in your ignition system, the PCM should throw a code. It could be anything, but will tell you that the cam or crank position sensor is bad. As soon as it does that, it starts running your car in total defense mode. The car runs like crap, but that'* because the PCM is winging the fuel/air/spark values to keep you from blowing the engine. The longer you drive, the more data the PCM has to smooth it out.

But that'* beside the point..

A dealer with a Tech II computer is the only way you tell for sure. I didn't go that route, because I have a boneyard that I go to, which always seems to have '95 at just the right moment. For $25, I can pull one and try it. I got lucky and it worked both times. The first time, after I had gone over everything in the entire ignition circuit. Just to check it, the Dealer will charge $50-$100. So I figured I'd take a shot at it.

I can pitch the"bad PCM" theory pretty well, because it happened to me twice. So, I'm biased by my personal experience. So, don't give it any more weight than any other suggestions.

As anti-Dealer and pro-Do-it-Yourself I am, if this situation continues to avoid solution, maybe you should take a shot at the Dealer. The money won't seem much compared to hours you'd spend on a problem which could be any air, fuel, or electrical problem. That'* a lot of ground to try to cover and you have no direction from a DTC code. And you are really taxing your drivetrain with that stutter.

All i can add to the discussion is.. if it'* the PCM and you can't do the boneyard crapshoot, a guaranteed PCM should not cost more than $100. For example.. (I can't recommend this specific store, because I never used them, but they look pretty good)

http://cgi.ebay.com/ebaymotors/GM-19...Q5fAccessories

I'm guessing, but I'll bet, theDealer will be happy to reflash the PCM for $2-300.

Good Luck.

charlie
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Old 01-16-2010, 03:33 PM   #20
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Well here I am in the garage, and so far the plugs looks perfect, so I assume I can rule out wires and coils. I checked the coils recently anyways, and they all tested ok. I'm guessing my next issue would be a vaccum leak. By my maf there is evidence of coolant seepage. If I were to take the olenum off to see why its leaking, would I have to get a new hasket for it? I have my other one, and it looks to be in pretty much mint condition. The ridge or whatever you want to call it is 100% intact. I'm guessing if there is signs of coolant, and all my hoses seem to be good, that my plenum might be a good place to start.
Any advice from the pros would be much appreciated.
Laters folks.
Ps, I sent this off my phone, so if there is typos I appolgize
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3.8. l67, 3800, bonneville, bonnie, hesitation, low rpms, misfire, ponitiac, rpms, se, sle, sse, ssei, stalling

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