Please Help!! 1999 Yukon OBS Surging when idling.

[tomb]

Kind of surprised there isn't a sticky for idle issues. Something like...
1. Verify no DTCs, fuel pressure, coolant level, strong battery (capacity ck), clean air filter, Ohms check ignition coil, ign source voltage & ground (zero resistance)
2.Verify plugs - AC IRIDIUM*; wires - Delco - OE*, cap & rotor - Delco*
*=recommended for reliability

 

[Panner99]

Kind of surprised there isn't a sticky for idle issues. Something like...
1. Verify no DTCs, fuel pressure, coolant level, strong battery (capacity ck), clean air filter, Ohms check ignition coil, ign source voltage & ground (zero resistance)
2.Verify plugs - AC IRIDIUM*; wires - Delco - OE*, cap & rotor - Delco*
*=recommended for reliability

Even searching I'm finding all different answers. On a good note you guys have all been a great help. Much appreciated. Ive posted these issues on other forums and not one person has answered.


I got my Dist cap today so going to put it on this weekend and see.

 

[tomb]

Very curious about the results of your cap replacement. I take great pride in keeping my truck running smooth. I changed the cap 30k ago and I'm experiencing an intermittent miss that isn't bad enough to spend money on. My truck has only 75,000 miles. I think I need to ohm out the coil just for peace of mind.

 

[Panner99]

I changed the cap saturday night. No difference. Still idles rough with the odd surge sometimes. Drives perfect though. Problem is ONLY at idle. I ordered wires and coil from rock auto. We will see what that does when they come in.

 

[tomb]

Since this is at idle, I assume you checked for vaccuum leaks? I mean with propane.

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[Panner99]

I will have to try that. I sprayed carb cleaner and couldnt find anything. It was the first think I did.

 

[Panner99]

I'm still at a loss. Its been cooler out so the idle has been a bit rough still. But yesterday it was hot out 88 deg F out. And the surging at idle was happening a lot.

 

[tomb]

Do you have access to a scanner? My harbor freight $50 scanner provides real time monitoring. Its good to verify outside and intake air temps. Coolant temps, short & long term fuel trims.

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[77Impala]

....
2.Verify plugs - AC IRIDIUM*; wires - Delco - OE*, cap & rotor - Delco*
*=recommended for reliability

I found out many years ago that GM engine management systems are very picky about their spark plugs. Long story short: Non GM plugs in your vehicle is very well known to cause idling problems. Be sure to use only the correct or GM recommended spark plug upgrade for your vehicle.

 

[tomb]

Oh yeah, very suceptable to pinging. (Pre-detionation) I had the original factory plugs in my truck, and it ping'd depending on outside temp. After a lot of research I went to the iridium OE equivilant delco plugs, blackbear tune optimized for premium fuel and have not had a problem since.