Runing rough at idle in P/N and on decel (11/14) - Page 3 - 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 09-27-2007, 12:22 PM   #21
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Quote:
Originally Posted by big_news_1
I assume you already checked battery and alternator output? Worth a shot, I say.
Sorry I missed that.

I have checked that before when I was toubleshooting a current draw that turned out to be a stuck antenna.

I'll check it agian though.
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Old 10-13-2007, 07:47 PM   #22
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I went out to Harry'* in Pennsburg PA today and picked up an engine harness.

I swapped the new one in and it still does the exact same thing.

I also verified it'* definitely not the IAC. I took it out, extended the stopper all the way, put it back in, plugged the harness into a different IAC on a spare TB and started it up. I also adjusted the idle screw so it idled where it normally does. Sure enough, the rpms started bouncing agian.

Any ideas?

This is driving me insane..
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Old 10-17-2007, 02:32 PM   #23
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This idea popped up into my head..

Would a stretched timing chain and worn dampener, play with the cam timing enough to make it run rough like that with no load?

No load would mean less tension on the chain and possible changes in cam timing.

Two things that make me think I may have worn timing components are:

1. I have about 40k on my cam with 90# LS6 springs but the first 10k were with stock retainers which means the seat pressure was more like 130# for 10k

2. When I crashed with this engine, I bent 3 valves. The bent valves must have been working agianst the cam and working against the timing components.

Anyone think it would be worth it to change the timing chain/dampner?
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Old 10-17-2007, 03:00 PM   #24
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I'm confused how crashing bent the valves. This does sound like it could be timing related. Is there a chance the timing marks don't line up properly?
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Old 10-17-2007, 04:27 PM   #25
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Wowzers... I guess you could check into it. See if the cam/crank are lined up properly. That would be crazy if it were the problem.

What about other things like small vacuum leak or PCV issue? I have a hard time believing a stretched timing chain would only manifest itself in no-load conditions. Not saying you're wrong... just thinking out loud.
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Old 10-17-2007, 04:37 PM   #26
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Quote:
Originally Posted by BillBoost37
I'm confused how crashing bent the valves. This does sound like it could be timing related. Is there a chance the timing marks don't line up properly?
I bent my rad support into the front valve cover and it caught 3 valves.
The timing marks were definitely aligned when I put the cam in 3 years ago.

Quote:
Originally Posted by big_news_1
Wowzers... I guess you could check into it. See if the cam/crank are lined up properly. That would be crazy if it were the problem.

What about other things like small vacuum leak or PCV issue? I have a hard time believing a stretched timing chain would only manifest itself in no-load conditions. Not saying you're wrong... just thinking out loud.
I have checked the PCV valve and theres no way any of the ports are clogged.
My vacuum is the same as before too.

Not trying to shoot down ideas either, keep chucking them at me.

Also, what about leaky injectors?
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Old 10-31-2007, 12:29 PM   #27
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I pulled the plugs this past weekend. They all looked pretty good and were very consistant. They have about 3k on them..

I am also loosing TCC lockup if I hold it at VERY light throttle on the highway.. I can clear the code and it will lock up all day long just as long as I'm going at a steady speed. It won't unlock under load unless it wants to drop down in gear. This leads me to believe the problem is ignition related.. I just don't know how.

Also the cold weather is helping the rpm bounce when decelerating, but it is still there.. The bouncing idle in P/N is the same..

Anyone have any new insight?
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Old 10-31-2007, 12:37 PM   #28
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TPS is good right?

Vacuum is good...

You've checked compression and know that all valves are sealing 100% right?

It'* nearly as good of a brain teaser as the switch you solved for me a couple years back.
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Old 10-31-2007, 12:37 PM   #29
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Just had a Brain storm of sorts...

Would the connector in the fire wall possibly have a couple of different pin locations?

The car you have had an L67, ans you installed the L36 with wiring harness..

Just a thought... Maybe its out there or Far fetched... But for some reason it came to mind

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Old 10-31-2007, 12:51 PM   #30
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Maybe I missed it, but how are your fuel trims? Any indication of a lean condition?
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