Please Help!! 1999 Yukon OBS Surging when idling.

redfishsc said:

I would still suspect the IAC, those seem to be iffy little creatures.

The range for the idle seems to be 400 to about 700rpm, which I think are the two idle rpm's for "warm" and "cold" engines. If you have the ability to read the coolant temp via the OBD2 system (which uses a different temp sensor than the dash gauge), you might find that this sensor is failing. I'm taking a wild shot in the dark here. I know my 99 Suburban typically idles at around 700 if cold, 450 if warm, although this varies.

Lately (this week) I've also been having rough idle, but it's been dropping rpm, not as rhythmic as yours either. Twice, it's stuck itself at 1700-1800 rpm idle as well, on a warm engine, in park... .which was a bit worrisome since I was 200 miles from home when it happened, with half the family (including an elderly Mom on oxygen).





Just out of curiosity, you say that it only has 81,000 miles, but the one in the video has 129+K miles. Not busting your chops or anything, but why the discrepancy?

Click to expand...

mattbrat004 said:

Did you add a nasty cam accidentally...

Click to expand...

Panner99 said:

Thanks redfishsc. I replaced the IAC and it didn't fix the problem. As for the miles. I'm in Canada so the gauge is in Kilometers. 129000 Kms is about 81000 miles. Sorry to hear about your truck. Seems these Vortecs can be a bit troublesome at times. Lol. I'm at a loss still. So many new parts. No resolutions.

Click to expand...

Panner99 said:

Thank you for the reply. The SUV only has 81000 Miles, would the distributor gear be worn yet???

I also forgot to mention it drives perfect. All this happens at idle.

Click to expand...

Panner99 said:

I actually was going through the invoices from the truck. The Dist cap and rotor were replaced last Sept 2016. So that rules that out. The only tune up things that haven't been changed were the coil and the plug wires.

Click to expand...