Low speed misfire in OD/lockup 3.8 V6 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 12-04-2005, 08:14 PM   #1
Junior Member
Thread Starter
 
Join Date: Dec 2005
Location: Pinehurst, NC
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
vanwill is on a distinguished road
Default Low speed misfire in OD/lockup 3.8 V6

My 1989 Bonneville with 3.8 V6 is the one car in my life I just can't part with. It has developed a strange misfire (?). It will only happen when the transmission is in OD and lock-up, and you carefully lug it down to about 1600 RPM. There are isolated jolts that feel like ignition misfire, except that they are very strong. It is not a string of misfires; it is one isolated "thump". Unless you press on the accelerator, the misfire does not cause any change in transmission state--if you continue to carefully lug at low RPM, it will "thump" again in a few seconds. It can not be made to misfire under any conditions other than this. Hard accleration--no misfire. Engine speeds above about 1800--no misfire. Does not seem weather related.

The misfires are so jolting, that I even suspected some trans problem where lockup went out-in quickly. However, my best clue so far is that when I replaced plug wires, the problem became noticeably worse.

ALSO, I need to replace the harmonic balancer, but I can't get the bolt loose on the crank end. The balancer appears smooth on its face, so I don't think a puller is required, just get the bolt out and the balancer will slide out.
vanwill is offline   Reply With Quote
Old 12-04-2005, 08:32 PM   #2
Junior Member
 
Join Date: Mar 2004
Location: Purgatory
Posts: 0
Thanks: 0
Thanked 0 Times in 0 Posts
harofreak00 is on a distinguished road
Default

just chirping in on your HB question...

i KNOW for a fact that you will need a puller... looks like this
harofreak00 is offline   Reply With Quote
Old 12-04-2005, 08:36 PM   #3
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

Your misfire isn't only under light load in OD. That'* when it'* MOST APPARENT. Change your plugs and wires. Typical symptom.

For the HB, you need to take the dustcover off your flywheel on the other end of the engine and jam something in there to prevent the motor from turning while you break the bolt loose.

Then use the puller.

You must jam something in there to prevent it from turning the other direction during re-install.
willwren is offline   Reply With Quote
Old 12-04-2005, 08:42 PM   #4
Junior Member
Thread Starter
 
Join Date: Dec 2005
Location: Pinehurst, NC
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
vanwill is on a distinguished road
Default

Willsren--thanks for reply. I have changed plugs and new wires. Plugs made no difference. Wires made problem noticeably worse.

Are there no HB'* that don't have to be removed with a puller? I'm familiar with that, and even have a puller stored somewhere, but under marginal lighting conditions I looked for threaded puller holes on the HB, but did not see any. I'll look again. Thanks.
vanwill is offline   Reply With Quote
Old 12-04-2005, 08:45 PM   #5
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

The threaded holes are on the back surface, accessed through the 3 slots in the front face.

You can rent a puller from Autozone if you have one nearby. It won't have the right bolts for the 3 holes, so you'll have to buy those seperately.

If your plugs and wires were changed, and your wires made it WORSE, I suggest you check each wire'* resistance and post the numbers here.

The only other possibility is your coil pack. You may want to consider a Type2 AC Delco upgrade from a 92 1/2 or newer GM V6 car.
willwren is offline   Reply With Quote
Old 12-04-2005, 08:54 PM   #6
Junior Member
Thread Starter
 
Join Date: Dec 2005
Location: Pinehurst, NC
Posts: 3
Thanks: 0
Thanked 0 Times in 0 Posts
vanwill is on a distinguished road
Default

Willwren--I'll look at the HB closer, but it appeared to have a smooth, convex front surface with no holes or slots. I've known the car since it rolled off showroom floor, so I'm sure it has never been replaced. It just started making a noise almost exactly like a rod knocking. Discovered that the elastomer joining the two-piece assembly together had turned loose, and I could rotate the outer (pulley) part while the center stayed stationary on the crank.

The "Type 2, AC Delco" upgrade--are you talking about just the assembly with the three squarish ignition coils?
vanwill is offline   Reply With Quote
Old 12-04-2005, 09:33 PM   #7
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

You want the ICM and 3 seperate coils off the newest 3800 you can find on the lot. jr's3800 can give you details on the upgrade and what bracket you may need. Well worth it. A hotter spark from the newer/better system will smooth out your idle and give you a stronger mid-range response in your power band.
willwren is offline   Reply With Quote
Old 12-05-2005, 01:18 AM   #8
Senior Member
True Car Nut
 
Join Date: May 2002
Posts: 2,936
Thanks: 0
Thanked 0 Times in 0 Posts
sse1990 is on a distinguished road
Default

It is very possible that you do need a puller for the HB, I was lucky enough that the engine out of the 88 trofeo I picked up came off without a puller, but that bolt IS a pita to get off.
sse1990 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Misfire at Low RPM slimsammy 2000-2005 12 03-02-2007 02:03 PM
What's your "Lockup speed"? theJMFC 1987-1991 8 05-22-2005 09:47 AM
Your TCC lockup shaking your Bonnie? HDvorider2001 1992-1999 2 01-25-2004 05:28 PM
Is this typical torque converter lockup/unlock? DMC 1992-1999 10 01-12-2004 12:42 PM
Rear wheel lockup...ABS goes looney -Help! 97BonneSE 1992-1999 4 03-01-2003 04:49 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 03:30 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.