Can you display those fuel trims as a simple chart? I’m not sure what to do with the “-“ sign in between the values. That said, these fuel trim numbers are a mess. I don’t know if I have ever seen such large negative values. I’ll wait for the chart before we launch into this but if I understand those numbers the computer is significantly reducing fuel control to compensate for a very rich condition. You might want to read this:

https://blazerforum.com/forum/2nd-ge...-trims-102906/


George

 

 

Not sure where the major negative numbers come from as it never goes that negative while I watch it. The one is from this morning going home the other shorter times one is at an idle after driving to work. I did have it hooked up to a friend's snapon scanner and it was showing the fuel trims as normal usage buy that was only at an idle and not driving.

 

Reading your post on fuel trims if I'm reading it correctly is saying possible vaccine line leak? I have replaced all the vacuum lines a few years ago as my 4wheel drive won't work at all with a leak. I haven't checked yet to see if the 4 wheel drive works since summer time when I took it off road for a bit to use it so I won't tie up. Will have to try it out again see if it does kick in the front wheels.

 

Your fuel trims look OK. You add ST and LT together for a given bank and you want to be under 10 absolute value. Your trims are positive so the computer is adding fuel for a perceived lean condition. If you have a vacuum leak then if you rerun those trims at 2500 the net positive numbers will go down. Just warm the truck up and read your trim values in the driveway at idle and 2500 rpm.

Is this problem the same no matter if the truck is warmed up and in closed loop vs cold?

When it will crank and not start look at spark during cranking at a couple of plugs both banks.

When it will crank but not start what is the fuel pressure?

Have you cleaned the throttle body?

Done any work on the IAT?

You should check the TPS values through the range with key on engine off


George

 

When it first started it only had issues when warmed up. Now it doesn't seem to matter warm or cold. I have ran 2 bottles of seafoam through the gas tank and one can through the throttle body. Plugs, wires, coil, cap&button and ignition module are all new. My coil was weak so I replaced it all at that same time. Last few days though it had been starting right up for the most part. I have checked spark and it is good. Fuel pressure is good though I haven't had a chance to run a permit gauge in the cab to see it every time. Hoping to do that this weekend. Fuel filter is new. Changed that out even though I didn't think it was the issue it had some miles on it so figured why not. What is so confusing to me is that once it does start it runs great with no hesitations or rough idle.