Topic: 91' runs great until warm
in Forum: C4 Engines
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I have been having problems with my 91' and looking for some advice. I have taken it out several times since being stored for the winter for about 15-20 min trips. Towards the end of the trip the engine starts to run/idle rough. Once I shut the car off I have to wait until the engine is completely cool until it will start and run again. It will crank and crank but not fire until it is cool. The SES light is not on. Has anyone else encountered this problem?
Thanks.
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lanoka harbor, NJ - USA
Joined: 3/22/2009
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Vette(s): 1990 L-98 white/ red/black leather interior targa top auto
1975 L48 blue/black leather interior t tops auto
might want to check your fuel pressure. i put in an adjustable regulator and not realizing it set the pressure to high. was ok on a cold start but when it warmed up it wouldn't start. readjusted it and everything was fine.
the dynamic duo
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Vette(s): 1985 Coupe-L98/Auto,Bright Red/Carmine.
1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.
I would be most suspicious of the HEI module, or the coil, first. It could also be a fuel problem. Best way to check that would be to install a pressure gauge on the fitting, and see what the pressure is when it starts cold, and then compare it to when it shuts down/won't start. Could be that the fuel pump is on it's way out, or maybe the "sock" filter on the end of the pick-up tube is sucking up crap from the tank, and stopping it up.
My bet is on the HEI module, from the description of the problem....
My bet is on the HEI module, from the description of the problem....
Joel Adams 
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My bet is on the injectors.
If they haven´t been replaced/cleaned previously.
Easy check is to measure resistance on them.
Just remove the clip on them, put the leads of a voltmeter (ohm scale) on the injectors contacts.
Cold, they should all read around 16 ohms, warm a bit higher (?).
Thing is, they should all read about the same.
I would bet you have one or two reading really low, like 5-9.
Are they grey colored, they would be the original ones, GM put them in the 89-90-91 models with a (then) better design.
Turned out they weren´t.
Almost everyone with those MULTEC´s have replaced them with better ones.
This is safe place to order them, http://fuelinjectorconnection.com/shop/
If it´s your problem of course.
in Forum: C4 Engines
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