HELP: Runs rough & dies @ light throttle - ZR-1 Net Registry Forums

jrtoffroad · 06-22-2012

Hey guys, hopefully you can help me out. Haven't done any real diagnostic work yet, but need to get this resolved ASAP as this is my daily driver right now.

The car is a 91' ZR1 (of course) in a good state of tune (new O2 sensors, new plugs, fuel filter, newish plug wires, MSD coils, new inj's installed before I bought the car). The car has had secondaries removed and has the appropriate Mark H chip.

Okay, so here's the symptoms:
- Since I first got the car (when it had the secondaries installed) it would sometimes act like it didn't want to run at light throttle AFTER heavy throttle accelleration. For example: WOT up to higher revs then take your foot out of it suddenly and it feels like there's no power unless you're above say 1/2 throttle, above which it fells normal. If you put the clutch in the engine will idle. This would always pass quickly, after driving just a mile or so.

-Recently the car has started to run very poorly after the engine has not been recently run (does not seem to matter outside temp). On start up it will idle fine, but trying to drive up my road sometimes the engine will start running VERY rough and basically die if I give it any throttle UNLESS I exceed 1/2 throttle, then it picks up and seems to run normal. Sometimes it will work through this (with me having to give it heavy throttle a few times) while other times the engine will just die and need to be restarted. Upon re-start then engine pretty much always runs fine.

-After driving a few miles the engine seems to run normal at all throttle positions, unless every once and a while the engine exhibits the lack of power issue after heavy accel I 1st mentioned.

-Finally yesterday for the 1st time the engine just died as I pushed the clutch in to turn into my road (this was with the engine warm and seemingly running fine). It re-started immediately and ran fine. Oddly when I got into my driveway and when from reverse to 1st the speedo flashed to 220mph for a second.

I have never had a check engine light. Could I have any stored codes without one?

Sorry for the LONG post! My thoughts at this point are to check the Throttle Position sensor and the primary fuel pump. Not sure if it's any different with the chip I have, but the secondary pump only runs at heavy throttle inputs correct??

Any other thoughts??

THANKS guys!

06-22-2012	#1
jrtoffroad Join Date: Sep 2010 Location: Colorado Springs, CO Posts: 75	HELP: Runs rough & dies @ light throttle Hey guys, hopefully you can help me out. Haven't done any real diagnostic work yet, but need to get this resolved ASAP as this is my daily driver right now. The car is a 91' ZR1 (of course) in a good state of tune (new O2 sensors, new plugs, fuel filter, newish plug wires, MSD coils, new inj's installed before I bought the car). The car has had secondaries removed and has the appropriate Mark H chip. Okay, so here's the symptoms: - Since I first got the car (when it had the secondaries installed) it would sometimes act like it didn't want to run at light throttle AFTER heavy throttle accelleration. For example: WOT up to higher revs then take your foot out of it suddenly and it feels like there's no power unless you're above say 1/2 throttle, above which it fells normal. If you put the clutch in the engine will idle. This would always pass quickly, after driving just a mile or so. -Recently the car has started to run very poorly after the engine has not been recently run (does not seem to matter outside temp). On start up it will idle fine, but trying to drive up my road sometimes the engine will start running VERY rough and basically die if I give it any throttle UNLESS I exceed 1/2 throttle, then it picks up and seems to run normal. Sometimes it will work through this (with me having to give it heavy throttle a few times) while other times the engine will just die and need to be restarted. Upon re-start then engine pretty much always runs fine. -After driving a few miles the engine seems to run normal at all throttle positions, unless every once and a while the engine exhibits the lack of power issue after heavy accel I 1st mentioned. -Finally yesterday for the 1st time the engine just died as I pushed the clutch in to turn into my road (this was with the engine warm and seemingly running fine). It re-started immediately and ran fine. Oddly when I got into my driveway and when from reverse to 1st the speedo flashed to 220mph for a second. I have never had a check engine light. Could I have any stored codes without one? Sorry for the LONG post! My thoughts at this point are to check the Throttle Position sensor and the primary fuel pump. Not sure if it's any different with the chip I have, but the secondary pump only runs at heavy throttle inputs correct?? Any other thoughts?? THANKS guys!