96 Buick #4 misfire, still chasing the problem
 

Just found this problem, engine light on showed a misfire. Had shop
double check all of the injectors and fuel pressure, all good. Install

a new fuel filter. Then did a new plugs. Thought it might be a spark
plug wire, installed a know good one, no fix. Then swapped with the
one next to it, still no fix. Replace coil, no fix. Replaced the ICM,
no fix.
Thought this could be related to the plenum problem noted here, not the
issue, the engine is not using any anti-freeze.
Tonight, I listened to all of the fuel injectors, all sound good.

Can a timing chain cause this kind of issue? It has never been
replaced on this car and it has 165k miles on it. However, why just #4
misfire. Overall, the engine runs great at highter speeds, only
misfires at idle.

96 Buick #4 misfire, still chasing the problem
 

--
Bing Bang Boom Viola Done!
> wrote in message
ups.com...
> Just found this problem, engine light on showed a misfire. Had shop
> double check all of the injectors and fuel pressure, all good. Install
>
> a new fuel filter. Then did a new plugs. Thought it might be a spark

What did the plugs look like? Did you happen to keep track of which plug
came from which cylinder?
The reason I ask this is because a spark plug would give indication if there
was a problem at the head, perhaps is a piston issue or perhaps a injector
issue!

> plug wire, installed a know good one, no fix. Then swapped with the
> one next to it, still no fix. Replace coil, no fix. Replaced the ICM,
> no fix.
> Thought this could be related to the plenum problem noted here, not the
> issue, the engine is not using any anti-freeze.
> Tonight, I listened to all of the fuel injectors, all sound good.

Your swapping items unnecessarily i.e. you could find yourself with more
issues then the present one!!
>
> Can a timing chain cause this kind of issue? It has never been
> replaced on this car and it has 165k miles on it. However, why just #4
> misfire. Overall, the engine runs great at highter speeds, only
> misfires at idle.

Could be a bad injector!

1st thing to do is a wet/dry compression test! This will help you determine
if it's internal or something electrical!

A scope will help determine if it's internal as well as a timing or
electrical issue!

96 Buick #4 misfire, still chasing the problem
 

96 Buick #4 misfire, still chasing the problem
 

> wrote in message
oups.com...
>I don't know about the bad injector. They did a pressure test and all
> looked good. Also, that is why I was listening to each injector to see
> if I could hear a difference. I am really wondering if I am seeing a
> misfire or could something else be causeing the rough idle.

Yes, a vacuum leak can cause a rough idle that can easily be mistaken
for a miss. s

96 Buick #4 misfire, still chasing the problem
 

"sdlomi2" > wrote in
:

>
> > wrote in message
> oups.com...
>>I don't know about the bad injector. They did a pressure test and all
>> looked good. Also, that is why I was listening to each injector to
>> see if I could hear a difference. I am really wondering if I am
>> seeing a misfire or could something else be causeing the rough idle.
>
> Yes, a vacuum leak can cause a rough idle that can easily be
> mistaken
> for a miss. s
>
>
>


In a feedback FI system? In my experience an air leak in a feedback FI unit
results in elevated or fluctuating idle.

--
TeGGeR®

96 Buick #4 misfire, still chasing the problem
 

Assuming compression is good, the lower intake gasket can get sucked in on
GM and cause a misfire.

--
Stephen W. Hansen
ASE Certified Master Automobile Technician
ASE Automobile Advanced Engine Performance
ASE Undercar Specialist

http://autorepair.about.com/cs/troub...l_obd_main.htm
http://www.troublecodes.net/technical/
http://www.familycar.com/Alignment.htm

> wrote in message
ups.com...
> Just found this problem, engine light on showed a misfire. Had shop
> double check all of the injectors and fuel pressure, all good. Install
>
> a new fuel filter. Then did a new plugs. Thought it might be a spark
> plug wire, installed a know good one, no fix. Then swapped with the
> one next to it, still no fix. Replace coil, no fix. Replaced the ICM,
> no fix.
> Thought this could be related to the plenum problem noted here, not the
> issue, the engine is not using any anti-freeze.
> Tonight, I listened to all of the fuel injectors, all sound good.
>
> Can a timing chain cause this kind of issue? It has never been
> replaced on this car and it has 165k miles on it. However, why just #4
> misfire. Overall, the engine runs great at highter speeds, only
> misfires at idle.
>