Rough Idle and choppy acceleration... - 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 04-04-2006, 12:53 PM   #1
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Default Rough Idle and choppy acceleration...

Hello,
I've searched the forum (as suggested) but couldn't find much specific info on my question. Of course, it could be that I just don't know what the heck I'm talking about...but that'* another story.

My vehicle is a 1993 Bonneville SSi
171,000 miles.

My issue has just started in the last few weeks. I'm getting a very rough idle when stopped, enough to shake the steering wheel and rear view mirror. Also, when I'm driving and try to accelerate, the engine goes choppy. I have to mash the accelerater to get it past the choppyness and then is speeds up. This chopy acceleration happens while on cruise too. Pretty much anytime gas is required to speed up.

I had a problem a few years ago where the car would act this way at slow speeds...like just starting off from a start. It would sputter and not want to accelerate until it either warmed up a bit or I finally got it rolling to a good speed. That problem was solved by cleaning the Throttle Body.

So, I'm not sure if this new problem is related to the Throttle Body or not. I've had one amature opinion on it...which was that the Throttle Body was getting clogged with Carbon Deposits causing the butterfly valve to stick...so, I thought I'd bring my problem here to see if anybody else could assit me.

Thanks for any help,
-Chris-
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Old 04-04-2006, 01:04 PM   #2
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Default Re: Rough Idle and choppy acceleration...

Hi Chris, Welcome to BC!

First some questions:
- when was the last time you had new plugs and wires? What brands?
- Have you worked on car yourself or by a mechanic/shop?
- Is it fair to assume there are no modifications?
- When was the last time you checked levels or changed your fluids? Oil, antifreeze/coolant?

Then I would suggest you open the hood and take a long look at things under there.
- Check the engine and transmission mounts for cracks or breaks.
- look at all the small vacuum lines and their rubber connections. Any cracks or breaks?
- any wires or connectors noticeably loose or worn?

If you've done all this, sorry for sounding patronizing. Just trying to get us up to speed.
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Old 04-04-2006, 01:36 PM   #3
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Default Re: Rough Idle and choppy acceleration...

Quote:
Originally Posted by lash
First some questions:
- when was the last time you had new plugs and wires? What brands?
- Have you worked on car yourself or by a mechanic/shop?
- Is it fair to assume there are no modifications?
- When was the last time you checked levels or changed your fluids? Oil, antifreeze/coolant?

Then I would suggest you open the hood and take a long look at things under there.
- Check the engine and transmission mounts for cracks or breaks.
- look at all the small vacuum lines and their rubber connections. Any cracks or breaks?
- any wires or connectors noticeably loose or worn?

If you've done all this, sorry for sounding patronizing. Just trying to get us up to speed.
Lash,
Thanks for the quick response...! And, no, you are not souding patronizing. Not to me at least. *grin* I really haven't spent a lot of time *looking* at the engine. So, I'll answer the questions that I can and get back to you once I take a longer gander under the hood.

-New plugs and wires? It'* been years...I coudn't even guess.
-All previous work...except for a couple of oil changes has been done by a mechanic.
-Yes, no modifications have been done to this vehicle.
-Antifreeze/coolant was just replaced in November.
-Oil changed last week.

In November, I had the waterpump flywheel throw its bearings and thus the serpitine belt slipped off. I had to drive it a bit after that and tried to keep it cool...but it overheated anyway. The mechanic that replaced the waterpump checked the Block pressure to ensure it wasn't cracked and he said it was fine. However, you can still smell a signifacant burnt smell on the engine.

I've driven it on a hefty delivery route since November so everything seems to be in working order. Its just been recently that this choppy acceleration has been going on. I don't know is that overheating from months ago would factor into this current problem...but I thought I'd give it to ya anyway! *grin*

Thanks,
-Chris-
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Old 04-04-2006, 01:42 PM   #4
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Default

Great start guys..

I would suggest a tune up.
Spark plugs (AC Delco or NGK)
Plug Wires (AC Delco or Belden)
PCV
Fuel Filter
Throttle body gasket and throttle body cleaner.

Go right on throught it changing out those old plugs, wires possibly clogged PCV and fuel filter. Also removing the TB and cleaning it extensively with the TB (not carb) cleaner.
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Old 04-04-2006, 01:42 PM   #5
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Default

Welcome to the club! I just got a car of your vintage, supercharged as well, and I hope you will fair better than I am at the moment....

Lash hit on a few good points, but also I would check the the coil packs...do a resistance test on them (should be in tech info), and also check the mounting plate they are on for any moisture that may be causing the coils to not fire right or at all.

Also pull the codes from the computer if any are stored. Tech info has that in there too.

Happy hunting! :P
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Old 04-04-2006, 02:10 PM   #6
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CJ, all recent mechanical issues can have a bearing on what is happening, so it'* never wrong to let us in on all info and history possible, as we're not there and can only "see" what you tell us, lol.

I would truely start by updating all the tune-up items. Until you've done the regular tune-up and maintenance items, like those mentioned by BillBoost, we're just shooting in the dark and throwing money at it. Once you've done that, and you still have a problem, we can start to eliminate potential issues.

Don't hesitate to ask any of the questions you need to proceed. Next thing you know, you'll be modding with the rest of us!
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Old 04-04-2006, 02:14 PM   #7
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Quote:
Originally Posted by BillBoost37
Great start guys..

I would suggest a tune up.
Spark plugs (AC Delco or NGK)
Plug Wires (AC Delco or Belden)
PCV
Fuel Filter
Throttle body gasket and throttle body cleaner.

Go right on throught it changing out those old plugs, wires possibly clogged PCV and fuel filter. Also removing the TB and cleaning it extensively with the TB (not carb) cleaner.

Great Advice


did you by chance clean the MAF sensor? this seemed to help my car idle better....also cleaning the IAC seemed to help it run better on startup, but MAF made the biggest difference.
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Old 04-04-2006, 02:39 PM   #8
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Default Thanks a lot!!

Wow,
This thread got off to a tremendous start!

Well, it looks like I've got a tune up to do! So, I'll get to it.

I really appreciate all the info you guys have given! I'll be sure to not get ahead of myself and get this tune-up done first. If that doesn't work...well, then I guess I'll be back for some more good advice! *grin*

Thanks again,

-Chris-
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Old 04-04-2006, 03:01 PM   #9
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Let us know either way!!! K?
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