Lanny81, are you referring to the ignition advance when you refer to the camshaft retard setting?

 

How hard would it be to check if the timing chain slipped by looking at the alignment of the distributor rotor when the crank is at TDC? If not too hard, it could eliminate timing chain slippage as the problem.

 

Do I read your posts correctly, measuring STFT+LTFT at a moment in time, you have seen values that range from -28 to +34? If so, that's extraordinary. Are the numbers without minus signs really pluses?

What happens to the way the truck runs at the moment it transitions from open to closed loop?

After closed loop are the O2 sensor voltages changing up and down above and below 0.5 volts?

You didn't waste your money but you have to be willing to walk methodically through the information that you are getting to take advantage of your scanner and to diagnose your problem. I will be glad to help you if that approach makes sense to you.

If the truck runs good cold then timing chains and distributors are not the likely problem. It's either something that craps out when it gets hot like the ECM, a sensor, a crAppy wire connection, etc or something that changes when you go closed loop.


George

 

George,

That is a good point: running fine when cold means the timing chain will likely not have slipped. (I know I keep coming back to that diagnosis! LOL)

Does that it runs well before warming up but bad after help pinpoint the sensor that could be bad? Are there sensors that are ignored until the ECM senses the engine temp is over 120 degrees?

 

Ya definitely runs better when cold. I just took it down road and if I ease into gas then it’s very smooth down the road. If I stomp it u hear spark knock and it spits and spitters as it gains rpms. Sitting in drive now at idle closed loop and it reads
Short term fuel 1 is 3.1
Long term fuel 1 is 19.5
Short 2 is 0.8
Long 2 is 14.1

 

The 3 o2 sensors seems to start at .050 area and go up to .935 area

 

If I hold rpm at 2k it runs very smooth and reads
Short1 -3.1
Long1 -10.9
Short2 -2.3
Long2 -17.2

 

Been holding pedal steady for few mins now at 2k rpm and reads
Short1 -2.3
Long1 -12.5
Short2 -2.3
Long2 -17.2

 

Just felt hesitation in idle and both longs would jump as shorts stayed at 0 almost

 

Those are minus beside these numbers too