Hello I have a 99 Chevy Tahoe that has a rough time starting but more so my main problems are high idle after start then goes to normal then back to high, as well as bogging down while driving till around 50mph, also when the engine is high idling it jerks into gear I have replaced the TPS, Ignition Control Module, Coil Pack, as well as the exhausts from the manifold to the rear pipe that comes out of the back basically the section that has the catalytic converters, as well as 3 of the 4 O2 sensors because the last one I havent been able to break free yet. I just need help in what direction I should go instead of just throwing more money at it and still having the same problems. The engine is the 5.7 V8 its the 4wd LS 4dr model with roughly 300,000 miles on the engine. Any help would be appreciated thank you!!

 

Have you put an OBD code checker on it?

 

Yea the last thing it popped up was to the one O2 sensor I haven't been able to get to yet and then the ignition control and said high voltage. I replaced the ICM and the coil pack together. The only thing it popped up after that was the TPS which is new but planned on replacing again anyways. I'm just at a point if what else can I throw at it in hopes that it will fix that problem as I'm worried its gonna jerk my tranny out from under the truck and I don't like the high idle with that motor having so many miles on it. Just really looking for someone with more experience and knowledge than I have to maybe point me in a direction I haven't thought of.

 

I owned my 99 suburban for 22 years and drove it from 27K to 240K and ended up replacing the O2 sensors at least once, but they never caused any running issues, just the "service engine soon" light . I never had your issues. At about 170K I replaced the rotor and distributor cap. The rotor contactor that rides on the center electrode of the cap was burned pretty bad and the 8 electrodes on the cap were pretty burned up, so you might want to check them. I'm not saying this is your problem but it would't hurt to check them. Just out of curiosity, what about the plugs and wires? My 99 never let me down.

 

I had the distributor and cap replaced about 20k miles ago. I'm gonna start with the TPS again and report back but in the meantime if anyone has any other ideas I'm open to hear them.

 

Just guessing, but those symptoms sound like the idle air control valve.

 

Branden: I hope to be able to help you on this! My 98 (300k) has the same issues and its just since the COLD temps here in MI.
I'm going to do more looking on it for ..? not sure, as its not triggering any codes. I'll be watching this thd. and when I get it resolved I'll luk what I did.
Good luck.