Hello everyone, I have a 03 Trailblazer with 150k on it. I have had the truck for a few years been running great. In the past few weeks seems like the idle is a little rough. I cleaned the throttle body and reset the computer. I changed the O2 sensor closet to the front, changed fuel filter, I had a suggestion to replace the variable timing solenoid which I did this week. Its seems a little better but still a little rough now and then. Any suggestions? Thanks!
Thoughts on semi rough idle?
- Thread starter Josh2012
- Start date
I always like to try the cheapest and easiest possibilities when troubleshooting a problem. I would start with cleaning the MAF sensor. After that, I would clean the IAC valve.
Question, do you use an oiled air filter like a K&N? If so and you recently oiled it, I would put money on it being the MAF and would give it a very thorough cleaning; use cotton swabs if you have a steady hand, if not just use the spray and let it air dry before reinstalling it.
Question, do you use an oiled air filter like a K&N? If so and you recently oiled it, I would put money on it being the MAF and would give it a very thorough cleaning; use cotton swabs if you have a steady hand, if not just use the spray and let it air dry before reinstalling it.
True.
What's a "rough" idle? Erratic rpms? Wants to stall? Sounds like you're on top of a few things and it could be worse! Is it only in D? Or startup? Too vague of a question. Way too many possibilities. Try running a few bottles of Techron in it for the injectors?
What's a "rough" idle? Erratic rpms? Wants to stall? Sounds like you're on top of a few things and it could be worse! Is it only in D? Or startup? Too vague of a question. Way too many possibilities. Try running a few bottles of Techron in it for the injectors?
What he said. Need a much more detailed description of the behavior at idle. Could be motor mounts. Could be plugs (no answer yet on when you changed the plugs and with what part number), an intake manifold leak from the classic loose bolt issue, or deteriorating compression that hasn't thrown a misfire code yet. Loose timing chain. Deteriorating coil(s) that haven't yet thrown a code.
Edited to add: What is "rough"?????? A 10 Hz rotational vibration that's worse in DRIVE and goes away in NEUTRAL? A ROM change that goes from 600 to 300 RPM every 3 seconds? If it's an RPM change, does it go away when you force the AC compressor off? A slight vibration that you can't see on the tach or don't think is caused by the AC compressor cycling?
Edited to add: What is "rough"?????? A 10 Hz rotational vibration that's worse in DRIVE and goes away in NEUTRAL? A ROM change that goes from 600 to 300 RPM every 3 seconds? If it's an RPM change, does it go away when you force the AC compressor off? A slight vibration that you can't see on the tach or don't think is caused by the AC compressor cycling?
I have yet to hear one bad thing about Chevron Techron for our GM trucks. I use it often. Runs like a champ. Beginning of motor mounts going? Slight vibration?
I just changed my motor mounts last week, and it is.......suuuh-moooooooothhhh. 
I had occasional roughness, some shakin', rough idle in gear, sometimes not. Again as I stated in that thread, I forgot how smooth this motor really is.
You have 10 year old mounts, they deteriorate very slowly but once new again the difference is instant. I say even if it doesn't solve your issues, at least you have new mounts, you really don't have much to loose and could possibly be the culprit. Just be sure you get OE GM mounts. Sorry to spend your money like that, but I can say the change with mine was a complete 180.
I had occasional roughness, some shakin', rough idle in gear, sometimes not. Again as I stated in that thread, I forgot how smooth this motor really is. You have 10 year old mounts, they deteriorate very slowly but once new again the difference is instant. I say even if it doesn't solve your issues, at least you have new mounts, you really don't have much to loose and could possibly be the culprit. Just be sure you get OE GM mounts. Sorry to spend your money like that, but I can say the change with mine was a complete 180.
Yeah I would keep an eye on your Tach while you are feeling the roughness. I didn't realize this could be caused by the start of motor mount failure (obvious now that it was suggested, but I'm new). I feel roughness in idle but the Tach is dead steady at 500 RPMs. Maybe that's my issue? Check yours it will help to narrow it down.
bLAzen03 said:I'm having the exact same issue. I'm at 145,000k miles
Changed plugs A/C Delco's, iridium's = No difference
Cleaned Throttle body = No difference
If I'm at a stop light & turn on the a/c the TB turns off.....
Hope it's not the ac compressor
No codes either.
What are the volts reading on the alternator when running? If they are strong while ac turns on then try a couple bottles of techron in the gas tank.
bLAzen03 said:I'm having the exact same issue. I'm at 145,000k miles
Changed plugs A/C Delco's, iridium's = No difference
Cleaned Throttle body = No difference
If I'm at a stop light & turn on the a/c the TB turns off.....
Hope it's not the ac compressor
No codes either.
How does it run with the A/C on while driving at speed, what about raising the RPM's while stopped to 1K then turning A/C on?
Try This but when you do, omit the battery disconnect and try pulling fuse# 10 first and see if that works.
When you pull the fuse, also pull the TB harness again to be sure it's fully seated.
Plug a scan tool in and check the RPM's. Are they fairly steady from 600-620 RPM? You have an 03 with 150K, I would very strongly recommend replacing your old motor mounts before you start throwing more money at it. The mounts are worn and aged, believe me when I say mine went from feeling like it's idling on 5 cylinders to like i'm in a 75 Cadillac stretch Fleetwood.
At the very least change the passenger side mount. When I changed the drivers side, reverse was smooth, when I changed the pass side, naturally forward was smooth but it was night and day.
At the very least change the passenger side mount. When I changed the drivers side, reverse was smooth, when I changed the pass side, naturally forward was smooth but it was night and day.
Update:
So it's fixed now, runs like a champ!
Problem/Symptoms:
1)The TB would turn off when I would turn the A/C on.
2)Very rough idle.
Performed:
1)Cleaned the throttle, again.
2)Changed the air filter.
3)Ran the re-learn...This however caused by battery to die.
4)Cleaned all the connecters leading to the throttle body with computer cleaner
I believe the a/c would cause it to turn off because it didn't have enough juice. It could of been a combination of all these things, but the bottom line is it runs GREEEAAT and smooooth!
Thanks to all for your input.
So it's fixed now, runs like a champ!
Problem/Symptoms:
1)The TB would turn off when I would turn the A/C on.
2)Very rough idle.
Performed:
1)Cleaned the throttle, again.
2)Changed the air filter.
3)Ran the re-learn...This however caused by battery to die.
4)Cleaned all the connecters leading to the throttle body with computer cleaner
I believe the a/c would cause it to turn off because it didn't have enough juice. It could of been a combination of all these things, but the bottom line is it runs GREEEAAT and smooooth!
Thanks to all for your input.