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Rough Engine Idle On 5.3


Charter Member
SM 2003
Full Member
Jan 26, 2002
Los Angeles, California
Anyone else experience a rough engine idle on frequent occasions. Mine has been doing this from the beginning. I didn't want to bring it in until I had some miles on it and now with 7000 miles it is pissing me off.

It doesn't matter if the engine is warm or cold or what the outside air temp is. The rough idle feels like a loping or missing. It gets the am/fm antenna moving pretty good.

I do have a FIPK and TB Spacer and am not looking forward to bringing in the truck to have the problem checked out only to hear routine answer, "It is probably a result of your modifications" I have had this problem before I installed the mods.
Mine has a "slight" miss in it every once in a while at idle, but I don't think it's anything that unusual for this engine. But its definitely not all the time, just notice it every now and then, and it's very mild. Believe me, as picky (some would say "peculiar") as I am about my vehicle, its nothing much if it doesn't bother me ;D

I took my antenna off the first time I got it washed, and haven't put it back on since... I thought it did way too much moving around like you were describing (even without your problem), and that it didn't look very nice on such a high end vehicle. Luckily, I ususally listen to CD's, and the couple of stations I listen to come in clear without it. Would be nice if they had a windshield antenna like my Regal GS had.

Well, if worse comes to worse, you could remove both the mods. and then take it back in so they'd know it wasn't them that was causing the problem.

I had this problem on my 99 Silverado and it was due to a faulty Throttle body.
I would double check to make sure everything in your intake upgrades are fully seated and not allowing for any air leakage of sorts......might cause the computer to read abnormally thus forcing it to make false adjustments.... :)
Mine is so dayum quiet I can not hear it idle. I have to turn the radio down and open a window.

Mine idles fine. Man these AVs are great huh!
This may not neccessarily have happened, but I have experienced it with other GM pickups. You may want to check the gap on your spark plugs. I have noticed on more than one GM truck in the past where the plugs did not come properly gapped from the factory. Just a shot in the dark but it may be worth a try.

I concur with Saint. My Dodge Ram (sorry for using the D word) ran pretty rough from day one. I had my mechanic put some different plugs in and it solved the problem immediately. In hindsight, I would imagine the proper gapping on the plugs had more to do with resolving the problem than the new plugs themselves.

I don't think it is plug related because it is an intermittent problem. It is only at idle and happens at different times. It is a minor annoyance but nevertheless it does bug me.

The problem with my Ram was only at idle too, but it was a pretty consistant problem. (not intermittant)

Examine your throttle plate and the air intake for carbon. ?If you find any, clean it out with fuel injection cleaner (not carb cleaner). ?Check your PCV valve. ?(I'm guessing) ?It is probably related to the IAC (Idle Air Control) or the EGR (Exhaust Gas Recirculation Valve). ? ?

Also, I would take it in to the dealer. ?Check all your plug wires. ?Remember, you have 8 coils. ?You may have a bad one and they can be intermittent. ?

I was thinking along the same lines. I know the intake is clean because I checked it today. I am going to bring it in.

I had a 2000 Land Rover Discovery II. It did exactly the same thing and the dealer told me it was normal on those engines.

I would love to hear Chevy come up with the same excuse. I am going to print out this thread and take it with me just in case.
I hope you get results from the dealer. I wish you luck. If you don't, take it to another dealer. :) :) ;D
You aren't the only one with this problem,a couple of weeks ago I was driving my wifes' Avalanche and it idled very rough. I asked her if it had ever done that before and she said that it did it two times but that it smoothed out the next time she came to a stop.
For me it idled rough every time I stopped at an intersection that day but hasn't done it since for either of us.
Please keep us up to date on this. :)
Well it is now next week and my AV is at the dealer. They just called me to tell me that they could not find anything wrong with the idle.

I told them to keep it overnight and tomorrow have the Service Manager sit in the truck with me while it is happening. It idles rough about 90% of the time.
You may have to find a dealer with a better service department :rolleyes:
OK, I sat in the truck with the tech and the scan tool plugged in. It showed what every cylinder was doing while we were idling. The idle wasn't that bad while we were sitting there. The way they explained it to me was that at an idle, the computer will idle the engine way down almost until it stalls and then raise it to keep it running at around 650 rpm. It does this to reduce emissions levels.

We took the truck for a spin with the scan tool still hooked up. All in all, the engine was actually performing better. The tech told me that they put some Chevron Fuel treatment with Techron in my tank the day before.
Then it hit me, I have been using from day one and to quote gandolphxx "California Wimp Gas" courtesy of Arco..

When I had my Land Rovers, They would only run their best when using Chevron gas. I think the whole Techron thing is really what modern engines work better on and considering that most of the Auto Manufacturers reccomend Chevron I think there is probably something to it.
Suddenly last week my 5.3 started idling rough. I took it in to the dealer yesterday. They said they cleaned the throttle body, but it's still idling rough. Going to take it back next week.