When i start my car the engine idles fine. But once i drive for a sec the idle will go way up to around 1500-1800 rpms and abruptly go back down again and it'll then idle around 900-1100 rpms. My pcv valve is fine and i don't think its the EGR. Could it be a lean idle mixture? Any ideas?

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Red '87FormulaFrebird
-mostly stock 5.0L LG4 V-8 w/cowl induction setup borrowed from '83 TA and T5 tranny. Hey stop laughing i just got it.

 

I also have the same problem and when I brake real hard after a acceleration the engine stops...

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Z28 -87 TPI
white with T-roof
red interior with leather seats
Wagner Borg rear axel
all options
all stock
check Website for info.
www.musikhuset.org/~po/camaro

 

possible leak thru the Throttle body gasket.
A bad Idle Air control valve.bad Throttle Postition Sensor,bad MAP. All these could not report any error codes.

 

My car is suppost to idle around 600, but its idling very very roughly at 500 or so. How do I fix this? Is it a carb adjustment?

 

what you have a craburator? I was taking about TBi.

IF its a carb. then check your choke. and vacumme leaks.

 

definetly check for vacuum leaks. this caused 70% of carb problems.

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'86 IROC 5-speed
305 LG4
edelbrock performer rpm intake
edelbrock 600 cfm carb
msd pro billet hei
'95 3.23 rearend
hotchkis rear suspension

 

Yes its carbed. Its kind of intriguing because when i go to work in the morning (when the engine is cool), and i first start it idles the way it should. Once i drive for not even a minute it'll idle really high around 1800 rpm for a moment (in subsequent start ups when the engine is still warm it doesn't do that) and then go back down to around 900-1100 rpms the rest of the time, which is a little high, but thats probably a carb adjustment. Could it be a faulty sensor/ECM/q-jet problem (my check engine light goes on about the same time the idle shoots like that for a moment)?

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Red '87FormulaFrebird
-mostly stock 5.0L LG4 V-8 w/cowl induction setup borrowed from '83 TA and T5 tranny. Hey stop laughing i just got it.

 

Well I had some spare time and a few bucks so I went and replaced my distributor cap, got a rebuild kit for the distributor, new plugs and wires, air filter and the little return filter thing. Its made a big difference in the idle, its idling at just under 600 now and its a whole lot smoother. It still drops to aroud 400 or so when you let off the gas from about 4k or so for a minute or so of idling before comming back up.