Engine or XMSN

[jwrussell]

Hey guys. Hoping I can get some ideas for solution to this problem I'm having. (2000 4WD Tahoe, 5.3L) Here goes: When I start it for the first time of the day, everything is fine. Idle is normal, no unusual noises or anything like that. Then, it will drive fine, usually a 20-25 minute drive to work. Then, when I get to work and put it in Park, the idle rpms jump up to about 1100 or so. Shifting into either Reverse or Drive prompts a noticeable clunk (can't be doing the tranny any favors) followed by the rpms dropping back to 500-600. Neutral will also idle at about 1100. Then, if I turn the Tahoe off and let it sit for awhile, usually 10 min is long enough, I can start it back up, and there seems to be no problem (idle is 500-600 through all gears, neutral and park). I'll drive it around again, and when I put it in Park, the high idle comes back.
To me it seems like something is warming up while I drive causing this, but I wouldn't think sitting for 10 minutes would be long enough for everything to return to normal. I would think if it was a vacuum leak, it would be there all the time, or get better when it warmed up. What do you guys think? And thanks in advance for the help.

 

[02tahoez71]

How dirty is the throttle body? Could be sticking? But i dont have much advice on this, seams very strange

 

[jwrussell]

I thought it might be the throttle body, too, but then today it did another weird thing. After driving for about 25 min, I put it it park and the idle was just erratic. It immediately jumped to 1100 or so, as it's been doing, then dropped to 500, then back up to about 800, and continued this for a few minutes while I sat there and tried to think of what it could be. I don't feel like its doing any damage, but it is driving me crazy. I'm thinking it's about time to take it to have a good diagnostics check done. There are no codes showing that the O'Reilly's scanner can see. I'm still hoping for suggestions from you guys. I'd like to fix this without having to pay someone. Thanks again.

 

[jwrussell]

Still hoping for some help on this. Probably going to take it to the dealer for a diagnostic check tomorrow if I don't get some kind of advice. I understand if nobody's had this problem before, but if you have any ideas shoot 'em my way. Thanks.

 

[jwrussell]

Problem Solved

Hello. Just wanted to let everyone know that the problem is fixed. I took a shot and guessed EGR valve. Turned out to be a good guess. Hasn't had the surging idle issue in about a week. I was hesitant about trying the EGR valve since I figured it would give a code it it was bad, but it didn't. Hope this might help someone else in the future.