'02 Tahoe Randomly Running Rough

[OR VietVet]

Definitely grateful for that! I apologize if my post came off otherwise.

It didn't come off bad at all. No worries. I am 67 and am not PC and never been a snowflake. I have no safe room. You can say and ask anything of me and the vast majority of members here. Now, get in there and start checking things that have been suggested. Plus, if you get it fixed, post back here that it is fixed and what was done. Helps others here.

 

[Fless]

Thought of another thing I think your truck has, and if the issue is mostly only at idle, the Idle Air Control (IAC) valve operation should be checked. It's on the throttle body.

 

[OR VietVet]

Like @Fless said. It will look like this. https://www.rockauto.com/en/moreinfo.php?pk=2596996&cc=1380372&jsn=920&jsn=920

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

You've already got a bunch of suggestions from folks here, so you can start to narrow down the variables and move toward a solution.

Last, be a two-way contributor to this Forum, and our shared knowledge base gets increased.

 

[GrandStang]

Didn't get a chance to work on it yesterday, but I left work yesterday and got back to work this morning without a hitch. That's what makes this thing so sketchy, that I don't know when it's going to strike next.

Thought of another thing I think your truck has, and if the issue is mostly only at idle, the Idle Air Control (IAC) valve operation should be checked. It's on the throttle body.

I read up on IACs, and the symptoms definitely match. Total noob question though... Is this something that can intermittently fail (explaining why it only happens SOMETIMES) or is it a "it's broken and it's not coming back" type deal?

 

[OR VietVet]

Anything that is mechanical and/or electrical can cause intermittent problems. Depends on conditions, weather, temperature, road conditions, the way the vehicle is driven, who may be driving it, etc............

I ran shops for years and if the customer at the counter was trying to describe a problem and when it happened, I wanted to know if it only happened on Sunday morning, turning left over the railroad tracks, when it was raining and at what speed. Anything that random was something I wanted to know.

 

[GrandStang]

Anything that is mechanical and/or electrical can cause intermittent problems.

Yeah, but there's certain things, like say a monitor, that'll either work or not work, there's really no "in between" or "kind of works." The joke we make is, "a woman can't be kind of pregnant, she either is or she isn't." lol

I ran shops for years and if the customer at the counter was trying to describe a problem and when it happened, I wanted to know if it only happened on Sunday morning, turning left over the railroad tracks, when it was raining and at what speed. Anything that random was something I wanted to know.

Amen to that! I work in IT so the more you know about the conditions, the easier it makes it to troubleshoot. Which makes this issue so strange to me. I live in Los Angeles, so the weather doesn't change much. The truck sat for just as long (from the time I got home, to the time I left for work the next day), so the conditions were essentially the same. So why did it do it yesterday morning and not this morning? I'm starting to think gremlins...

 

[OR VietVet]

Even a monitor can have an intermittent connection problem. After that happens and I get mad enough to punch the monitor, well it is a hard fail at that point and not intermittent.

 

[Larryjb]

Do you have access to a scan tool? It can be useful to know if the miss is only on certain plugs, one bank, or random throughout.

Another thing it could be is intake manifold gaskets. I had trouble diagnosing mine and in the end had to take the chance on it. You are supposed to be able to flood propane around the intake manifold gasket and see if you get RPM changes. This didn't work for me so maybe I did it wrong. I think the clue I got was from the scan tool telling me my fuel trims were high indicating a vacuum leak. But the scan tool was very useful here and is a valuable investment. If you have the $$$ to spend on one, get one that can at least record driving data. One that can cycle the ABS pump for bleeding is a bonus for the future.

 

[RTLINGR2]

I agree with the other members. Check the basics first, scan tool, check for misfires, fuel pressure, and if have access check for technical service bulletins (TSB's). I vaguely remember seeing a TSB on random misfires that had to do with broken ground wires in the harness behind the drivers side head. There are grounds on the backside of each head. Some of which are the grounds for the coil packs.

Yes I know this is extra money, but any time I buy a used vehicle I always change all fluids, filters, and do a a tune up, check over steering, suspension, brakes and tires. This way i know where i stand with all the maintenance.