1994 Silverado 5.7 L V-8 Auto. 235k
My truck had the 4L60E rebuilt about 100 miles ago.
It shifted smoothly & on time.
Now something has changed, it jerks on starts & stopping. To the point of almost 0 rpm
The 1-2nd shift points have changed now & it slightly revs like 500 rpm higher on shifting into 2nd gear.
The torque converter was not replaced on the rebuild.
The trans. guy says it’s either a bad TPS or ECM (computer)
The only other strange thing is that recently with those same symptoms, the engine has been very hard to start. Cranking over & over, until I pour about 1/2 oz. gas into the throttle body.
then it finally starts, missing heavily like flooded for 5-10 secs. then idles & restarts with no problem??
So I’m thinking these problems are related.
I thought maybe it could be bad gas (water) ?
I think that is still a good possibility?
What is the best way to confirm water in the gas? And eliminate the water if found?
Maybe break the gas supply line at the fuel filter & catch some in a glass jar?
And let it settle out for awhile?
I will be replacing the TPS, MAP sensor & IAC valve today.
I have not had a problem until after I sat the truck unused for 3-5 days at a time, several times.
Do you think possibly water settled to the tank bottom and is in all of the fuel lines causing the low performance, very hard starting & jerking.
Any good way to test & confirm a bad ECM ? This truck is a 1994 but it was built right before OBD1 came out later that year.
Thank you for your help!

 

Please let me know if the TCC fuse is in the underhood group? I see several in line fuses? Could a bad brake switch be the problem with TCC not disengaging properly? Thanks