08 5.3, runs smooth in park/neutral rough idle in gear

[akbrener]

As stated, 08 tahoe with 185K, runs great, idles smooth in park or neutral when the RPMs are a tad over the "500" dash, but put it in gear and the idle drops a needle below the 500 mark and seems to get an intermittent miss and RPMS will bump around a bit. very random, no rythm or pattern. Temperature does not seem to have any effect on it.

Within the last 5,000 miles I have done oil change, ACdelco plugs, new AC delco wires, upstream O2 sensors, and always run top tier gasoline with a bottle of Chevron Techron every 3rd fill up.

Throttle body was cleaned last year and didnt look too terrible, seems like the rough idle came into play about 10K miles ago.

Curious if anyone has had this issue on their vehicle, wouldnt really be concerned too much other than the fact that it runs real nice and smooth when not in gear. Clean the throttle body again? maybe injectors? Thanks.

 

[drakon543]

could also just be something simple have you rechecked the tuneup? weak or improper spark can show itself more pronounced under even a slight load change.

 

[akbrener]

02 sensors, spark plugs, and wires were all changed a week apart to check for any improvements. Idle issue did not disappear. The parts were due though so not a total waste.

 

[OR VietVet]

Basics first, so go to auto parts store and get the MAF cleaner and follow instructions on the container. I also am just going to ASSUME you have a 5.3 engine, instead of the 4.8 or the 6.2 options for engines. Signature is a great place to share that or type it in your post. What is the fuel pressure reading when in gear?

https://www.rockauto.com/en/moreinfo.php?pk=9551044&cc=1441040&jsn=2242


I need to do a better job of seeing that engine size in your post. My bad. BUT, if you post without that engine size info then I at least have to guess. Again, sorry but still would be better with all info in the signature.


Edited to include what James had mentioned: https://www.rockauto.com/en/moreinfo.php?pk=3944205&cc=1441040&jsn=2244

 

[swathdiver]

As stated, 08 tahoe with 185K, runs great, idles smooth in park or neutral when the RPMs are a tad over the "500" dash, but put it in gear and the idle drops a needle below the 500 mark and seems to get an intermittent miss and RPMS will bump around a bit. very random, no rythm or pattern. Temperature does not seem to have any effect on it.

Within the last 5,000 miles I have done oil change, ACdelco plugs, new AC delco wires, upstream O2 sensors, and always run top tier gasoline with a bottle of Chevron Techron every 3rd fill up.

Throttle body was cleaned last year and didnt look too terrible, seems like the rough idle came into play about 10K miles ago.

Curious if anyone has had this issue on their vehicle, wouldnt really be concerned too much other than the fact that it runs real nice and smooth when not in gear. Clean the throttle body again? maybe injectors? Thanks.

I would say the stumbling is because your idle is now too low Andrew. So what caused that? I would like at the throttle body and TPS sensors for starters.

 

[Doubeleive]

at 185k a new maf should be in the game plan I see them typically start taking a dump around 160k just food for thought.

 

[BG1988]

sometime this is a sign the tras is going out

 

[akbrener]

Thanks for the input. I will take a look at the Throttle body and MAF again this weekend. I figure with 185K, and ownership for 100K its probably time for something that needs more than normal tune up stuff.

I fogot i have the torque app on my phone with the bluetooth reader, will throw it in and see if anything drastically changes before or during the rough periods.

 

[BG1988]

could be many things even a slight misfire

 

[OWSI]

If you find anything out on this let me know. I have a 2007 Tahoe LT with much the same issue. 5.3 litre. 164,000 miles on it. Trans rebuilt by Aamco at 123k. 4 cyl mode feels like a cylinder drops out completely at any speed. Idle rough like a cylinder is gone with repeated "bumps". Missing feeling at 42-45 mph under steady light throttle with torque converter locked up in V8 mode accompanied by bouncing tach needle. Sometimes will do the same at 55 mph. Step on it and it pulls smooth and hard to all shift points, no feeling of a miss at all. Looked into the computer- fuel trims short and long term within 1.0% both banks. No misfires stored. MAP and MAF readings within expected parameters. Cat efficiency ok. Only goofy thing is it feels like a rough idle in drive. Put it in reverse and its pretty darn smooth. Rev to 1200-1300 in neutral or park and it feels like intermittent misfires. No stored or pending codes in the ECM. No check engine light ever. Plugs, wires, injectors, air filter all replaced. No help. Have swapped in a new coil to several positions (non afm cylinders), no help. Injector swap recommended by local shop which also cleaned MAF and throttle body. I'm stumped and ready to pull the last of my hair out.