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.

Runing rough at idle in P/N and on decel (11/14)

Old Sep 16, 2007 | 12:46 PM
  #1  
95naSTA's Avatar
Thread Starter
Senior Member
True Car Nut
 
Joined: Feb 2003
Posts: 4,508
Likes: 2
From: Philly
95naSTA is on a distinguished road
Default Runing rough at idle in P/N and on decel (11/14)

My idle is rough in park and neutral and my scantool is showing misfires on all cylinders. If I put it in drive, the misfires go away and it idles smooth.
Another thing is, at certain speeds when I decelerate, the rpms come down and bounce between 1500 and 2k.
Those problems will only happen if the car has reached operating temp too.
Other than that the car runs great and pulls hard.
There are no codes either.

Everything I've checked / tried:
Fuel pressure : Good
Vacuum : Good
Fuel Trims : Good
EGR tube has no cracks
Cleaned the MAF
Fuel system cleaner

Swapped:
IACs
ICMs
PCMs
Plugs and wires are new
Tried stock 95' TB with stock MAF and TPS, no change
Edit : swapped EGRs too

I also tried increasing values in the Commanded Airflow vs. RPM vs. Gear Ratio Table. This is what controls the decel rate. This also did not cure the rpm bouncing on decel.

I had to repair my engine harness from my accident too. I soldered and shrink tubed everything and searched hard for any damage. If I see a 95 SE at the yard I'll grab the harness and try it out.

So, any ideas?
Reply
Old Sep 16, 2007 | 02:41 PM
  #3  
big_news_1's Avatar
Senior Member
True Car Nut
 
Joined: Jun 2004
Posts: 3,459
Likes: 1
From: Glendale, AZ
big_news_1 is on a distinguished road
Default

Jeez... after everything you've already tried, I would be mystified.... Don might be on to something with a bad ground?

This is a tough one...
Reply
Old Sep 16, 2007 | 10:21 PM
  #4  
95naSTA's Avatar
Thread Starter
Senior Member
True Car Nut
 
Joined: Feb 2003
Posts: 4,508
Likes: 2
From: Philly
95naSTA is on a distinguished road
Default

Hmm. I know the ground from the battery to the body is good but the engine to battery may not be.
Instead of bolting it to the block I bolted it to the same stud the ICM is grounded to...

Ok, I ran outside after I typed that and relocated that ground to the block under the front header. I sanded it down too.
It still does the same thing when it'* warmed up. :(
Reply
Old Sep 17, 2007 | 09:28 PM
  #6  
bobc997615's Avatar
Senior Member
Posts like a 4 Banger
 
Joined: Nov 2004
Posts: 122
Likes: 2
From: bloomington, in
bobc997615 is on a distinguished road
Default

I had a cracked coil post which caused my SSE to add funny.
Reply
Old Sep 17, 2007 | 11:08 PM
  #7  
95naSTA's Avatar
Thread Starter
Senior Member
True Car Nut
 
Joined: Feb 2003
Posts: 4,508
Likes: 2
From: Philly
95naSTA is on a distinguished road
Default

Originally Posted by jr's3800
Only does it in open loop... Interesting..

I am at a loss
Well, the decel problem comes on after the first couple stops when the engine is just heating up.

The misfire in P/N starts when coolant temps are 130* or so and it gets worse as it increases to operating temp (180-185ish)

I'm going to go to the yard this weekend and see if they have a 95 SE. I'll grab the engine harness if they do and I may try adding another ground before the weekend.
(I'm actually on travel till Thursday)

I did have all the coils off a couple times and didn't see any cracks. I'll check agian later in the week. Can't hurt.
Reply
Old Sep 18, 2007 | 01:30 AM
  #8  
big_news_1's Avatar
Senior Member
True Car Nut
 
Joined: Jun 2004
Posts: 3,459
Likes: 1
From: Glendale, AZ
big_news_1 is on a distinguished road
Default

It'* random/multiple misfires, right? So no way to track a misfire to a different cylinder if you switch the coils around? See if you have more misfire counts on any particular cylinder, then switch coils and see if it changes. I can't imagine all 3 coils failing at once, though :?

You already tried everything I would have thought to try. Maybe you got a bad bunch of plug wires? Might want to try testing them...
Reply
Old Sep 18, 2007 | 10:12 AM
  #9  
95naSTA's Avatar
Thread Starter
Senior Member
True Car Nut
 
Joined: Feb 2003
Posts: 4,508
Likes: 2
From: Philly
95naSTA is on a distinguished road
Default

Originally Posted by big_news_1
It'* random/multiple misfires, right? So no way to track a misfire to a different cylinder if you switch the coils around? See if you have more misfire counts on any particular cylinder, then switch coils and see if it changes. I can't imagine all 3 coils failing at once, though :?

You already tried everything I would have thought to try. Maybe you got a bad bunch of plug wires? Might want to try testing them...
When the misfires start, they alternate between all the cylinders then all cylinders misfire when it warms up.

I've had a bad spark plug wire before and it would only arc under load. Should I check the resistances?
Reply
Old Sep 26, 2007 | 09:42 PM
  #10  
95naSTA's Avatar
Thread Starter
Senior Member
True Car Nut
 
Joined: Feb 2003
Posts: 4,508
Likes: 2
From: Philly
95naSTA is on a distinguished road
Default

So,
Now when I'm in really heavy traffic,
on my way home from work,
the engine is well heat soaked and coolant temp is as high as it gets (190ish),
AND I'm completely stopped in drive,
the engine will randomly feel like it'* missing and the RPMs will dip down and come back up.
I haven't had this happen in drive before..
This will only happen when it'* hotter out. It'* cooler in the morning and this dosen't happen on the way to work.

I tried shaking various parts of the engine harness while the engine is hot and missing in park but it dosen't effect it at all.

I went to the u-pull today to get another engine harness. This is the second time since my last post I've gone and they still don't have a 95 L36.. It'* really suprising. They always have them..
I'll try agian next week.

Tonight, I added another ground to the front of the block and I sanded the crap out of where the battery connects to the body.

It still does the same thing in park and during decel. It didn't miss in drive but it'* much cooler out.

Any more ideas??
Reply

Thread Tools
Search this Thread

All times are GMT -4. The time now is 09:18 AM.