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Stock '87 GT 5-speed with engine shake at idle, need some ideas by hdryder
Started on: 04-30-2014 07:53 AM
Replies: 22 (231 views)
Last post by: hdryder on 05-09-2014 12:37 PM
hdryder
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Report this Post04-30-2014 07:53 AM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have a stock '87 GT 5-speed with a minor, but annoying, engine shake at idle. I have tried a number of things to correct it, but have not yet found the problem.
I have even brought it to a couple of repair garages to help locate this problem, but still have not been able to pin it down.

Off idle the car runs pretty well and this engine issue does not really seem evident. It almost seems to be a balance issue, but only noticable at idle.

At the two garage's suggestions I have done the following: Replaced spark plugs, plug wires, cap & rotor, Idle Air Control Valve, and sent off fuel injectors for cleaning.
I installed a new fuel pressure regulator when I was installing the cleaned injectors.
I also have a new catalytic converter on the car that was installed a year or so ago.

Thank you for the help.

[This message has been edited by hdryder (edited 05-01-2014).]

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Csjag
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Report this Post04-30-2014 08:30 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Have you checked for trouble codes? Try running some good cleaner like sea foam thru the throttle body.
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Report this Post04-30-2014 08:32 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post

Csjag

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Also look at the engine while its running in the dark and see if you can spot any spark arcing and clean the ground straps and add another ground strap from the engine to the chassis
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hdryder
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Report this Post04-30-2014 08:38 AM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
Good ideas. Thanks.

I have added an additional ground strap about a year or so ago.
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hdryder
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Report this Post04-30-2014 10:21 AM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Csjag:

Try running some good cleaner like sea foam thru the throttle body.


What is the best way to do this procedure?

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Report this Post04-30-2014 10:27 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Its harder on the V6 but the best way is to idle the motor and squirt it in the throttle body as you work the throttle to keep the motor running as it will want to stall as you spray the seafoam in. If it stall just restart it and continue
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trotterlg
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Report this Post04-30-2014 03:04 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
Has the engine ever been replaced? Larry
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hdryder
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Report this Post04-30-2014 03:17 PM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

Has the engine ever been replaced? Larry


As far as I know it is the original engine.
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ag9123
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Report this Post04-30-2014 03:36 PM Click Here to See the Profile for ag9123Click Here to Email ag9123Send a Private Message to ag9123Edit/Delete MessageReply w/QuoteDirect Link to This Post
Worn out engine mounts and/or dog bone?

------------------
1984 Indy Fiero

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Gall757
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Report this Post04-30-2014 03:37 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

Has the engine ever been replaced? Larry


This is a long shot, but if the flywheel was resurfaced and reinstalled in the wrong position, you would get this kind of vibration....I don't know how you would prove that though.

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trotterlg
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Report this Post04-30-2014 04:32 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
It is difficult to put it on the wrong way, but if it was replaced with the wrong one that is what you will get. Larry
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Report this Post04-30-2014 04:50 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Even engine timing being off can cause vibration at idle, timing could be retarded.
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hdryder
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Report this Post05-01-2014 05:44 AM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Csjag:

Its harder on the V6 but the best way is to idle the motor and squirt it in the throttle body as you work the throttle to keep the motor running as it will want to stall as you spray the seafoam in. If it stall just restart it and continue


Does Sea Foam come in a spray can? I may have only seen it in a pour can.
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Report this Post05-01-2014 07:02 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes it does, try the parts stores
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hdryder
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Report this Post05-01-2014 07:42 AM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Csjag:

Even engine timing being off can cause vibration at idle, timing could be retarded.


I will double (re-check) the timing this weekend.

The bottom motor and trans. mounts have been replaced. The dog bone (Torque Strut Mount) has not been replaced yet.
The dog bones that I have brought home from the local parts stores, that are supposed to fit, do not fit. They are the wrong length.
If I can find the correct one that fits, I would like to replace it also.
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Report this Post05-01-2014 08:32 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
You could get the adjustable dogbone from Rodney Dickman Fiero or order one from Rock Auto parts. How far off have the Auto Parts one been, you do have to rock the engine forward to replace it.
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hdryder
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Report this Post05-02-2014 07:40 AM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Csjag:

How far off have the Auto Parts one been, you do have to rock the engine forward to replace it.


The dog bones at the local parts stores, when they carried them, were about 4-3/4" from bolt hole center to bolt hole center. No local parts stores are now carrying them in stock.

The dog bone on my '87 GT 5-speed is about 4-1/8" from bolt hole center to bolt hole center.

If anyone has a part number for an available OEM Torque Strut, I would like to have it.
Otherwise I most likely will locate some poly bushings for the original stock dog bone.

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Report this Post05-02-2014 08:22 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
I wouldn't use poly bushings in the dog bone on a stock engine IMO. The engine was designed to have the rubber bushing dog if you have the regular engine and tranny mounts putting the poly in creates an unbalanced situation.
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hdryder
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Report this Post05-02-2014 11:05 AM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
[QUOTE]Originally posted by Csjag:

You could get the adjustable dogbone from Rodney Dickman Fiero or order one from Rock Auto parts. /QUOTE]

The Torque Strut listed on RockAuto, DEA Part # A2396, is the same part used on the '82-'91 Pontiac 6000, which has the bolt holes center to center distance about 4-3/4".
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Report this Post05-02-2014 01:34 PM Click Here to See the Profile for FIEROPHREKSend a Private Message to FIEROPHREKEdit/Delete MessageReply w/QuoteDirect Link to This Post
When you replaced the plugs and wires did you clean out the di-electric grease out of the spark plug wires? I know they put this grease in the wire boots and it can cause weak spark issues. The di-electric grease is not to make better electrical conduction but to seal out moisture. Also check your timing. Inspect the magnet portion of your distributor for a cracked magnet. It will be the little six point star looking thing under the rotor.

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ARCHIES JUNK IS FASTER THAN SHAUNNA'S JUNK

12.3 is faster than a 13.2

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Report this Post05-02-2014 06:25 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Sorry if Rock Auto doesn't have the right size, I assumed they I because they did for my 2M4, I will have to look elsewhere too for my GT
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Report this Post05-08-2014 10:41 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Did you ever get you rough idle taken care of?
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hdryder
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Report this Post05-09-2014 12:37 PM Click Here to See the Profile for hdryderClick Here to Email hdryderSend a Private Message to hdryderEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Csjag:

Did you ever get you rough idle taken care of?


Not yet. I am going to remove the Throttle Body, maybe this weekend, and do an inspection and cleaning.
Also, may check Coolant Temp sensor for ECM for it's condition. I think I replaced it last year, but not positive.
I also have a smoker for vacuum leak detection a friend sent me that I will try to use asap.
I looked at the Harmonic Balancer while the engine was running at idle to see if there was a wobble, but did not see one. Someone at a local repair shop said if it was bad, a wobble maybe visible while the motor is running.

Thank you for all the ideas.
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