heat related idle/run issues, need more brains

[Sully]

So, I am selling my truck. It had sat for a few months, but started right up. It ran fine for a few minutes, but when it warmed up it started to rev hunt at idle. Then it surged big time and backfired like a SOB. It dies if you give it gas or leave it be.

I have tried:

fresh gas

fuel injector cleaner (lucas)

cleaning the IAC/TB as well as seafoaming the motor.

popping the gas cap off (incase of vapor lock)

replaced the cam position sensor (had codes for it, but they are gone now still have the same issues)

I have unplugged the batteries and left them for a while as well as touched pos-neg cables together.



I have also noticed the #8 header gets glowing orange if trying to rev during the back fire BS. I havent looked at the injectors or the spark plugs because I am thinking they would be the issue from the start up, not just when it gets warm.


for those who dont know me, i have a 97 1500 with vortec 5.7l and damn near everything is new as I have rebuilt the ever loving crap out of this thing.


And go.

 

[DRAGGIN95]

It sound's like it start's running bad when the truck goes in to closed loop mode when the temp warm's up, do you have a live data scanner to see what the O2 sensor's are doing?

 

[Sully]

interesting thought. I dont have live readout, but I can data log and read the log after. I am sure I will be able to see the O2s at that point.

 

[DRAGGIN95]

Yeah that should work, it may not be your problem, but I have worked on a truck where both bank 1 and bank 2 sensor 1's were not working, and just as soon as the engine warmed to the point where it would normally go in to closed loop the engine would fall on it's face and not run worth a crap.

 

[Sully]

sounds like my issue.... im warming the truck now and once its gets to opperating temp, I'll log it

 

[Sully]

data log didnt work.... I forgot these trucks werent supported until 98.

I unplugged the O2s and it didnt change so I have to assume thats not the issue

 

[Sully]

ok, truck is idling rough but idling with the O2's unplugged. it would have died by now. Its steady and running now

 

[ndians68]

kinda sounds like water in the distirbutor

 

[Sully]

water in the dist.... nope. I had it all apart to replace the camshaft position sensor. And water in the dizzy makes for no spark and no running at all

 

[nate3531]

vacuum leak on the EGR valve? If the EGR is working correctly it shouldn't backfire. I had a leak on mine, fixed that and it ran like a champ.