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Idle Problem Now.....

2008wagon

By 2008wagon
in Ask A GM Technician

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2008wagon Enthusiast

2008wagon

Posted
Posted

When the guy starts this truck in the morning after sitting all night the idle sometimes jumps immediately to about 2500RPM for like 3-5 seconds, then settles down to normal. Or, it just hangs at 1500 forever refusing to come down at all.

Then other times it runs great for days not doing any of these things.

No engine light, no codes, seems to run really good on the road.

Suggestions? IAC, throttle body, MAF maybe, TP sensor??

Stevens03 Senior Enthusiast

Stevens03

Posted
Posted

I'd start with cleaning the MAF sensor and throttle body. IF that doesn't cure it, then start looking for a vacuum leak or at the PVC.

2008wagon Enthusiast

2008wagon

Posted
  • Author
Posted
I'd start with cleaning the MAF sensor and throttle body. IF that doesn't cure it, then start looking for a vacuum leak or at the PVC.

 

I found some leaves stuck in the MAF screen, the throttle body was very sludged, and the IAC was caked with crap. So I cleaned everything up, we'll see what it does now.

I has now another problem, the fan and water pump pulley are ungodly loose, see the thread I started about it, if you would.

bossier62guy Senior Enthusiast

bossier62guy

Posted
Posted
I'd start with cleaning the MAF sensor and throttle body. IF that doesn't cure it, then start looking for a vacuum leak or at the PVC.

 

I found some leaves stuck in the MAF screen, the throttle body was very sludged, and the IAC was caked with crap. So I cleaned everything up, we'll see what it does now.

I has now another problem, the fan and water pump pulley are ungodly loose, see the thread I started about it, if you would.

 

 

How did leaves manage to contaminate the MAF? Have you been running the truck w/o a filter? If leaves got that far there is no telling how much other shit got sucked up into your engine.

2008wagon Enthusiast

2008wagon

Posted
  • Author
Posted
I'd start with cleaning the MAF sensor and throttle body. IF that doesn't cure it, then start looking for a vacuum leak or at the PVC.

 

I found some leaves stuck in the MAF screen, the throttle body was very sludged, and the IAC was caked with crap. So I cleaned everything up, we'll see what it does now.

I has now another problem, the fan and water pump pulley are ungodly loose, see the thread I started about it, if you would.

 

 

How did leaves manage to contaminate the MAF? Have you been running the truck w/o a filter? If leaves got that far there is no telling how much other shit got sucked up into your engine.

 

 

No, this isn't my truck. He's a friend of mine. There were two pieces of leaf stuck right up against the screen, I took pics of it to show him. I have no idea how they got there, the filter is very clean and apparently had been changed recently.

txab Senior Enthusiast

txab

Posted
Posted

Did you clean the MAF with MAF cleaner? It's very easy to damage the MAF. I'd be very careful when removing objects stuck to it

C6Racer Enthusiast

C6Racer

Posted
Posted

The recent air filter change is an obvious clue that the old filter was probably in there for too long and the rubber strip around the perimeter was probably coming off allowing the filter to sag and air to get around it. It's a VERY common problem. I use MAF or brake cleaner at work to clean the MAF. They work great and have never had any problems. As for the throttle body, my college auto instructor always said, "If it's not clean enough to eat off of, it's way too dirty". It is always best to completely remove the TB and both the TPS(don't try to clean the TPS itself though) and IAC valve for a VERY thorough cleaning.

Good luck! :D

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