Question-------------------------
Followup To
Question -
Hello ED:
I purchased a 95 k2500 at a local farm auction
last 8 # ov vin are SE135037
It is a 5.7 4x4 with a 4l80e tranny was rebuilt last year according to previous owner.
The starts fine idles ok it tends to just about stall before it does it surges back to life.
While driving it tends to shift fine up to 4th
around 80kms or 50 mph ( not sure where you are)
When you let off the gas and back on to it
the tach and engine stall and won't do anything until it reaches around 1000 rpm then it hits and takes off again.
I brought this unit ito GM they thought it was the o2 sensor they changed it . Then changed the ecm. still nothing.
I brought the truck home having invested too much money at GM.
I took it to a local garage yesterday with three
guys who love GM.
They have pulled their hair out with it.
They have changed the Catalytic converter thought it was the problem only to find out that the problem was still there.
They tried 4 different map sensors
looked for vac leaks.
Checked fuel lines to and from the tank.
They describe it as running fine once started.
then choking it self out with too much fuel.
it has a new fuel filter
wires plugs cap rotor air cleaner
oil change as well.
timing is perfect top dead center 0
new exhaust from cat back walker brand.
I have dumped a can of slick 50 injector cleaner
during the hair pulling. :)
The boys at the shop tell me that the fuel pressure is perfect I believe they said between 9-12 psi.
The only thing that was not change was the prom
which has been carried over.
I also sought out another ecm from the exact same year and truck . Same number 16197427 different prom #.
The only difference between the truck was the other on was an extended cab. With a stright swap it started fine backed up fine put into drive and little to no power and backfire and stall.
They want to tear apart the tbi in the morning.
Any suggestion we would be greatful
Thanking you in advance
michael
Answer -
Hi Michael,
Check the TPS or replace it and see if it takes care of the problem,also install the original prom into the replacement ECM,though it may be the same truck,the prom calibrations tend to be different.but it sounds like you have a TPS that is failing.
ED
HEllo again ED!
Thanks for the info
However it is still acting up.
The truck has 185 000 KMS. or 110 000 miles
The original prom has always stayed with the truck. Now through 4 ecms
As of today
the following has been changed
New converter
ecm
oxygen sensor
ingition module
ingition coil
fuel filter
fuel pressure regulator
T.P.S.
M.A.P. sensor
injectors.
9-12 lbs fuel pressure as all time.
We hooked up an inline pressure gage for a road test.
The oxygen sensor seem to want to rich out the mixture as the truck drives down the road causing it to choke out.
When we bypass the oxygen sensor leaving a fixed fuel ratio
the truck runs fine.
We even bypassed the oxygen sensor off the ecm with a new wire.
still the same.
Can you think of amything else we may have over looked?
We are really stumped.
Thanking you in advance.
Michael
AnswerMichael
Hmm,we got some data good,ok,why would the O2 want rich?only if it sees high oxygen content in the exhaust stream,it thinks the engine is running to lean,any exhaust leaks?even a little one can cause O2 sensors to read lean,also check the intake manifold for leakage,check the throttlebody both the base gasket and the throttlebade shaft for any vacuum leaks,what we got to figure out is why the O2 is sending a lean signal to have the ECM dump more fuel,and check the coolant sensor,make sure that isnt shorting out causing the ecm to think the engine is still cold.ill do some more research on this,i love the challange. :)
ED
