Hi,

My IROC seems to hesitate under hard throttle in the first 1/2 hr of driving and the rev counter fluctuates (a bit like a broken speedo) After 1/2 hr it gets better but doesn't totally pass. It's been a while sine I've changed the plugs, do you think it could be that? My ZZ4 is carb (750 dp) and it has the distributor that came with the engine..

I'm thinking maybe a plug lead or possible the plugs, but would that effect the rev counter..

1 other thing although the rev counter isn't reading true, the engine under light throttle and tick over is fine.

Please help me, thanks

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'86 Iroc ZZ4
Best Run 13.8 @ 100mph
I told you to blow the bloody doors off!
The British Firebird/Camaro Site

 

Sounds to me like its non of the above and more of the obvious. YOUR FIRING SEQUENCE is wrong. You can get it half way there and have it run. I did this once and it ran silly but it was still out of sequence. Check to make sure its right.

 

Thanks for replying. I think though that as the car has run absoultely faultlessly since day one since the engine was put in, it is a recent thing. Any other ideas?

Thanks

 

you postive when you changed the plugs you didn't get them out of order?? I'd double check just to be on the safe side. Could be cracked plug to, not to sure on what else it could be. I'd do a simple visual inspection, just look over it real good and check out all your leads and ends. Just my 2 cents

 

Definately not firing sequence Any other ideas? Could it be the plugs (12,000 miles)

 

Hey, I just changed my plugs/wires the other day. When the car started I could hear a clicking, or popping noise, but thought is was one of the injectors (would have bet money on it being #1 or #3). The tach just bounced and fluttered like I've never seen one do before. Drove it, definately had a light miss. Couldn't see anything till it got dark. #5 plug/wire not right - small lightning storm down there. Pulled the cap off and put it back on (right) and the tach was steady and the miss gone. I've had wires crossed up before (non-computer car) and never seen the tach jump around like it did on the 86 IROC. Must be something to do with the computer when spark to one plug is interrupted, or intermittent. Check it out.

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Z's r Best

 

Sorry, forgot about the time I had a cracked distributor cap on the 73 Laguna. Ran like several spark plug wires were crossed up (popping/cracking out the tail pipes and back through the carb) till the engine was warm enough to evaporate the moisture out of the cap. Changed the cap and rotor - ran like a top. Try starting it up, let it run 5 or 10 minutes (till it starts getting warm) and then cut it off and let it sit 5 or 10 minutes and restart it and see if it smooths out. That stop at 7-ll 5 minutes from work always cleared my miss up quicker than driving on down the road.

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Z's r Best

 

Check all the coil connections, it may just be a loose or dirty connection. How old is the coil? A weak coil will cause a miss or hesatation under heavy throttle. Check all your plugs and then change them, get good wires and if that don't fix it replace the coil, I'm assuming the carb is ok, Holleys are real sensitive to trash getting into them, but it would not make the tachometer (rev counter for u British) jump. Good luck

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92 Camaro RS 5.0 5-Speed (Quasar Blue)
T-Tops
14" Open Air Cleaner
3.08 Posi-trac
Edelbrock TBI Intake
Crane cam
Ported & polished stock heads 3 angle valve job
HyperTech Chip
SLP Headers (Ceramic Coated)
UltraFlo cat-back exhaust

74 Dodge Dart Sport 360 (11.2 1/4 mile)

2000 Dodge 1500 Ram Sport

 

Thanks a lot guys, will get down to it tonight... and the car

I'll keep ya posted.