Idle problems

[jacek11]

I have 1990 c 1500 and i got problem, when engine its cold wont stay idle , when worm will die out after running for a while mostly when i stay at stop light. So far i replaced Idle air control sensor and still the same problems. Please help !!!

[wally91vhevrolet]

i had this problem with my truck a while back, ive replaced so much its hard 2 say exactly what fixxed it, check your injectors and be sure there sprayin right, also check your vacuum and EGR valve and EGR solenoid, check your IAC valve for built up carbon and clean it out real good, if u get a new one be sure its set right and the pin isnt to far out or too far in or it wont function right

[jacek11]

Originally Posted by wally91vhevrolet

i had this problem with my truck a while back, ive replaced so much its hard 2 say exactly what fixxed it, check your injectors and be sure there sprayin right, also check your vacuum and EGR valve and EGR solenoid, check your IAC valve for built up carbon and clean it out real good, if u get a new one be sure its set right and the pin isnt to far out or too far in or it wont function right

Thanks i will try EGR valve and solenoid first and we see

[steve3320]

I will bet money it's your egr valve/system -------- I just went thru the same thing with my '89. Cap off the vacuum port coming out of the TBI that goes to the egr and see if this fixes the problem. The computer will set a fault code when you do this, but the engine will run correctly if the egr is your problem. If oyu have had your vacuum lines off for any reason recently, or like me, just purchased the truck, make sure they are hooked up correctly. The egr line should pull little to no vacuum at idle. Hope this helps

[jacek11]

Originally Posted by steve3320

I will bet money it's your egr valve/system -------- I just went thru the same thing with my '89. Cap off the vacuum port coming out of the TBI that goes to the egr and see if this fixes the problem. The computer will set a fault code when you do this, but the engine will run correctly if the egr is your problem. If oyu have had your vacuum lines off for any reason recently, or like me, just purchased the truck, make sure they are hooked up correctly. The egr line should pull little to no vacuum at idle. Hope this helps

So far changed EGR valve and solenoid , IAC (check lenght of pin) and still the same problem maybe even worst HELP !!!

[2000CAYukon]

jacek11,
I would disconnect the Engine Coolant Temp Sensor when the engine is cold (near the tstat in the intake manifold). This tells the computer that the engine is really cold. If it idles correctly (when cold), the sensor may be bad.

On my 90 K1500, I had a rough idle only when warm and it turned out to be the pickup coil inside the dist (dist must be pulled to replace).

I assume you have checked for vacuum leaks and did a tuneup. Also check the PCV valve.

//2000CAYukon

[jacek11]

Originally Posted by 2000CAYukon

jacek11,
I would disconnect the Engine Coolant Temp Sensor when the engine is cold (near the tstat in the intake manifold). This tells the computer that the engine is really cold. If it idles correctly (when cold), the sensor may be bad.

On my 90 K1500, I had a rough idle only when warm and it turned out to be the pickup coil inside the dist (dist must be pulled to replace).

I assume you have checked for vacuum leaks and did a tuneup. Also check the PCV valve.

//2000CAYukon

OK i put new MAP sensor when disconect vacum line idle its fine but run like crap, when i put vacum line back on wont stay idle, any sugestions?

[jacek11]

After changing all electronics EGR MOP , pickup coil ... i found the problem in insuficient fuel pressure replace fuel pump and couple rusted fuel lines and truck finnaly running like brand new. Thanks to all who try to help me with this problem.

[slythee]

Originally Posted by steve3320

I will bet money it's your egr valve/system -------- I just went thru the same thing with my '89. Cap off the vacuum port coming out of the TBI that goes to the egr and see if this fixes the problem. The computer will set a fault code when you do this, but the engine will run correctly if the egr is your problem. If oyu have had your vacuum lines off for any reason recently, or like me, just purchased the truck, make sure they are hooked up correctly. The egr line should pull little to no vacuum at idle. Hope this helps

I have a '93 c1500 5.7 that also idles rough when warm. I looked at the EGR system and cant see exactly what it recirculates. It seems to be hooked up to itself. Can anyone send me a pic of what it looks like or point me to a schematic or soemthing? My Chilton manual sucks! and doesn't show a good pic.

[slythee]

Originally Posted by 2000CAYukon

jacek11,
I would disconnect the Engine Coolant Temp Sensor when the engine is cold (near the tstat in the intake manifold). This tells the computer that the engine is really cold. If it idles correctly (when cold), the sensor may be bad.

On my 90 K1500, I had a rough idle only when warm and it turned out to be the pickup coil inside the dist (dist must be pulled to replace).

I assume you have checked for vacuum leaks and did a tuneup. Also check the PCV valve.

//2000CAYukon

Do you have a traditional points distributor or the HEI system?