The car has been sitting for quite some time, so we are just getting it back up and running again. We swapped out to bigger fuel injectors (was tuned for 36, now there are 42s). The car starts up and idles fine when cold, but when it warms up, it starts missing. Since it has had the same cap/rotors/wires for probably 8+ years, (98% of this time the car was just sitting in the garage), we are going to replace those and see, but what do you all think it could be?

 

Probably the tune in closed loop. going to 42lbs over 36's will change things alot at idle. Needs chip burnt for 42's and then watch what it does in closed loop operation. Adjust as necessary to get it running smoothly.

You never did answer the question, what system are you running? Is it stock electronics still?

 

During a cold start, and in Open Loop, the Integrator is set to 128 and locked there. The coolant temperature reaches a threshold value, a timer says the engine has been running long enough, in turn setting the stage for the O2 sensor to dictate long and short term fuel adjustment in Closed Loop. You need to tune for the larger injectors because your running 6% more fuel, and although the ECM can correct for it, it is only making it's job all the more difficult. The closer you get to 0% correction, the happier you will be....

 

interesting! Orr89, pm coming your way

 

double

 

turns out it was a dirty fuel tank!

 

Get a new fuel filter too while your at it and maybe have your injectors cleaned? Some injector cleaner might work

 

thanks for the tip!

 

Hi i am new to these forums, i seem to be having the same problem, my 91 z28 camaro 305 tpi runs great cold, when it warms up like (20 min) it starts to have a rough idle. I originally had a service engine light with a code 52. I replaced the ecm, service engine soon light came off but now idles poorly when hot. Cars completed stock with 52 000 only Ive replaced the battery, thermostat, cap, rotor, plugs, oil, air filter, fuel filter cleaned the ignition module and used silicone before securing it. Not too sure where to go from here, i dont want to keep buying parts and guessing

thanks

 

try replacing the temp sensor, i was having alot of problems with my 86 z and replacng part after part and a friend suggested the temp sensor, havent had a check engine light since and my idle problems have ended