02 HO great idle cold horrible idle hot

S

steveo24

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Apr 21, 2009
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I need some help here guys. I was brought an 02 2500 4X4 6 spd with a crazy idle problem. Here is a breif description of what is going on---
First off there are no codes. Secondly the guy who brought me the truck just bought it, so there is no known history. HO truck stock all except for a replaced VP and a FASS unit. I start the truck and thje idle quality is smooth and nice all until it hits about 100 degrees on the scanner, then it ramps up to around 1100 rpm and shakes badly. I have changed to another set of injectors and no difference. Fuel pressure is 20 psi at all times, and it drives great. You wouldn't know there was anything wrong with it if you never seated the clutch and let it idle. I have ran a few scanners on it and there are no codes. I am pulling my hair out, don't know which direction to turn:bang

Here is a video, it actually gets a whole lot worst it was a bit cold in this video

 
Check to see what your intake air temp.(IAT) sensor is reading when this happens. It might be lying to the ecm. Either that or there's some internal or circuit board issues with the vp.
 
IAT seems to be in check, the Map reads 14 psi at idle so I know it is bad, got another one coming. The only thing that reads funny on the scan tool is the CMP RPM, it is a flat lined 0. I have changed the Cam sensor to another one and it made no difference. If you unplug the sensor with it running, the idle smoothes out but high idles to like 16/ 1700 rpm and the tachometer drops off, so I know it is indeed working. ??
 
02 ecm's are weak. could be a potential ecm hardware failure creeping in
 
Thanks for the reply. It's funny that you replied, I just got done putting my smarty on it to see if indeed the ecm would take a tune and it did. Without knowing the history, I wanted to see if anyone had put in a tune and not removed it. It took the tune ok, but now on the data display it won't display but 4 PID's??? When I look up under system tests, it won't display cylinder shutoff perameters like it did before only read VIN pid, and when you select it it says VIN is not programable?????? I have never seen this before. I am putting another set of good known injectors in the truck tomorrow out of my truck and we will see how it runs, I am down to 2 possibilities I think --- The ECM and the IP???
 
I thought I read somewhere that the MAP is an absolute pressure sensor, so shouldn't it read 14 psi at idle (atmospheric pressure)? Could be wrong on this though!!!
 
steveo24,
Did you get it figured out/what the problem was?
I am having the exact same issues & would really like to resolve this.
 
Sounds kinda like mine but mine is more of a lope. Ive done put Sticks,ip, IAT,Fixin to put new ecm. I still aint figured it out.
 
Jehri said:
steveo24,
Did you get it figured out/what the problem was?
I am having the exact same issues & would really like to resolve this.
Click to expand...

Sure didn't. The owner decided to wait a while and just upgrade into other parts...
 
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