RPM's keep shooting down especially in IDLE
 

I have an 08 Chevy Silverado Z71 4x4 LT V8 5.3L. While driving and coming to a stop in Drive my RPM's shoot down and back up causing the truck to vibrate that is very noticable by anyone in the truck. I'm thinking a fuel issue, not too sure. I did take the throttle body off and cleaned it well. It stopped the problem for about a day but its right back at it and there is no way that throttle body is dirty that quickly. Any suggestions before I bring it to the dealership and pay a 90$ Diagnostic fee.

First Off If There is a light on take it to your local parts store theyll scan it for free. second sounds like a possible miss fire So I would Check spark plugs wires and coil if you take it to parts store and its on a specific cylinder take it to the chevy dealer there might be something bigger wrong and lil more costly

As simple said, if the check engine light is on, that would be the place to start. If not, then you have other things to check. How many miles on the truck? If you do replace the plugs, USE ONLY AUTOLITE IRIDIUM spark plugs. In my experience, usually a plug wire rarely goes bad unless it burns or rubs against something. Additionally, a coil is usually indicative with a miss under a load.

Pull the plug and measure the gap. At 70k miles, I did not notice only a small gap difference between the old and new plugs. However, my truck drove great afterwards.

Also, our trucks front O2 sensors are prone to fouling out. I found it easier to pull off the tires and remove the inner plastic fender shroud to replace both the plugs and 02 sensors when I replaced my spark plugs.

When you cleaned the throttle body, did you use a throttle body cleaner that is teflon safe? I can't remember if Chevy throttle bodies are teflon coated but I believe all modern throttle bodies are.

How's the air filter? If you have a K&n (or if one was installed), you may want to clean the mass airflow sensor. They make a special cleaner for MAS

Hope this helps and keep us informed

Thanks for the ideas guys, the truck has 58k miles on it, the air filter I replaced when I cleaned he throttle body. I was along the lines of the spark plugs and wires but I figured it would do it while I was driving also and not just in idle but then again it could be I just don't notice it. I'm going to take a look at the MAS get back to you guys on that. The engine light is not on, it came on after I cleaned the throttle body but thats because I didnt reconnect correctly but in case I was wrong I got the code for what was wrong but it was for the reason of not plugging it back in. I'll make sure to keep you guys updated thank you

Good luck georgia, Plz keep us up to date. If you resolve it, we wil be able to offer that info to the next guy (or ourselves) :) with a similar problem.

As stated use MAS (MAF) sensor cleaner, nothing else. Another important thing, make sure you don't have any air intake leaks. All the combustion air has to be measured by the MAF,(MAF=mass airflow).

Ok so I got a chance to really dig in today, I found one of the spark plug wires was rotted and I'm assuming didn't have a good connection. So I made the move to Autozone to replace all 8. On the way their the engine light was blinking and I'm positive it was because that plug had to be completely out because the wire was deteriorated. Also the ride there was rough also due to one of the plugs being out. I got there bought a new set of wires for the ruck, they are a little bit longer then the AC Delco ones Chevy uses, no I didnt buy bosch I bought duralast wires. I replaced the wires one by one and went to start up the truck to find the engine light stayting on. I got the code read it was described as the 6th cylinder had a misfire. So now I'm in somewhat of a new predicament. Either with these new chevy's the engine light wont go off without the machine turning it off or the spark plugs were bad but I took them out and they looked fine all gauged fine they weren't rotted. I'm not sure what to do I can get the engine light turned off if I want, what is your opinion? The truck runs fine rpms dont shoot down my MPG's have slightly gone back up. Also does anyone know the cylinder count, I called a dealer to find out but they said I should take it in, probably to get a few bucks out of me. I'll look it up onlineand post what they are unless ya guys know them already. Ahhhhhh it's always something

yeah, a mis fire code WILL reset itself after you drive it for a while. It just takes a while. I would recommend going to autozone and have them reset it for you. If you have the misfire still, it will trip it again. Additionally, it takes one hell of a miss (like the one you described on the way to the store) to trip a mis fire code. So if you don't feel anything, you are probably good.

I would break down and get a obd II code reader, you can read your codes and then clear them right there without all these rides to autozone.