I need some help here fellas, I have a 2000 new body Tahoe with the 5300. My trouble is the idle, it fluctuates between 7-800 and 2-300 and acts as though it cant "find" its idle setting, almost like the compressor kicks in and out but its not. The fuel filter is changed regularly and otherwise no other engine running issues. I was thinkin throttle pos. sensor but dont know much about the newer stuff, any help is greatly appreciated. Thanks
Don't go replacing parts willie nillie. Without looking at it, you might wanna clean the throttle body, as that can cause a fluction in idle. Take it to autozone and check it for codes. Do not buy parts based on the code! If it has a code, post it up and we'll go from there. Leaking fuel pressure regulator is pretty common as well, but you usually have an extended crank condition as well. Does it take longer to fire up (first start of the day) than it used to?
How many miles are on it?
Is the compressor kicking on? Have you looked at the AC pump and pulley to see if it is spinning as one whole piece?
Fires up quick as always, and sometimes will idle perfect no matter temps, problem shows itself no matter temps. 165,000 miles. Compressor is working properly.
check the tps, throttle position sensor. in the manual it should give you the ohms to check for, its not that hard ta do...sounds like the issue
It'd be much easier to diag with a scan tool plugged in.Seriously, clean the throttle body, it's cheap and easy. If that doesn't help, you might have to take it in.
Will clean it up and check ohms tommorrow, see if that helps. What would an extended crank issue be?
It'd be much easier to diag with a scan tool plugged in.
If you clean the throttle body make sure you use "throttle body and manifold cleaner". It will not damage the other components like carb cleaner will. I think you also need to make sure you don't get any on the Mass Air Sensor.
check the tps, throttle position sensor. in the manual it should give you the ohms to check for, its not that hard ta do...sounds like the issue
Short of scanning it, the best way to check it would be to backprobe the signal wire at the tps with a high impedence dvm. You will be looking for around .4-.8 volts at idle and a smooth transition to 4.6volts as you open the throttle to full open. You can do this with the key on and engine off. You can also "massage" the harnes while it's running to try to induce the condition. This will help you locate wiring issues like broken wire or poor connections.
Come to think of it, check the positive battery cable connection. Make sure it is clean and tight.
If its drive by wire (no throttle cable) clean the throttle body. Kachina26 is right on the money with that one. You'll see a buildup right where the thottle blade meets the bore. Get that squeeky clean and your good to go. We see this one a lot.
If the thottle is cable actuated, carry on with checking for codes TPS sensor and IAC position actual vs. commanded. Let us know what you find.
Jay
Posting Permissions
Reply With Quote