91 rough idle
07-05-2011, 01:16 AM
#1
Instructor
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91 rough idle
I'm sure you guys have been through this a bunch of times but here we go. I've got a 91 ZR-1 with roughly 20,000 miles, we bought the car with just over 13,000 miles about 5 years ago. The car started to develop a rough idle around 14k, we replaced the spark plugs and seemed to clear up the issue for about 1000 miles. The rough idle started to return, but wasn't too bad. Now the idle has been getting worse and worse. When starting the engine cold it runs fine after it has warmed up the rough idle begins. Pulled the plugs out today and 4 of them were very fouled out (center and side electrode were very dark). I have search the forums and have found that the possible issues could be bad injectors, bad ignition wires, or bad ignition coils. Through your personal experiences with your own cars what is most likely to fail?
Only mod is B&B exhaust, but idle problem occured long before the exhaust. Regular maintanance (fluid changes).
Only mod is B&B exhaust, but idle problem occured long before the exhaust. Regular maintanance (fluid changes).
07-05-2011, 06:37 AM
#3
Le Mans Master
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Dittos on the injectors. Pre 93 injectors were suseptable to alcohol dissolving the internal coil insulation, resulting in the coils shorting. DO NOT replace them with "new" old stock (NOS), as a GM dealer did on mine before I bought it. I can tell you they will last about 3 years before they too will begin to crap out!
I replaced mine with the Accel 150821 injectors ($588 from Summit Racing for all 16). You'll have to grind off a little plastic alignment tab on 8 of them in order for the original connectors to fit - no biggie. And, the difference in idle and over-all performance has been surprising! Idle is very smooth now.
P.
I replaced mine with the Accel 150821 injectors ($588 from Summit Racing for all 16). You'll have to grind off a little plastic alignment tab on 8 of them in order for the original connectors to fit - no biggie. And, the difference in idle and over-all performance has been surprising! Idle is very smooth now.
P.
07-05-2011, 09:31 AM
#4
Another vote for shot injectors. Check out these documents by Marc Haibeck:
http://www.zr1specialist.com/HAT%20W...eplacement.pdf
http://www.zr1specialist.com/HAT%20W...in%20Place.pdf
http://www.zr1specialist.com/HAT%20W...eplacement.pdf
http://www.zr1specialist.com/HAT%20W...in%20Place.pdf
