Have a 1994 5.9 1500 2wd. had it for 4 years never a problem, until lately. The truck will roll over and flood itself out, but if i remove the fuel pump relay it will start right up. if i leave the relay in and i floor the pedal while cranking it will stumble and start up and blow alot of fumes out the pipe if i keep the rpms high. this had me thinking maybe low fuel pressure causing the injectors to spit, had 40psi at the rail but replaced pump anyways. here is all i have done to it since it started acting up....


New fuel pump
New o2 sensor
new Map sensor
new tps sensor
new ECM
new IAC motor
New cam sensor(coil pickup)
New ignition coil
new plugs
new wires
checked wiring physically and using schematic to ECM good ground and positive.

Also i checked vacuum for leaks and found the vacuum line going into the throttle botty full of little tiny rubber *****. completely clogged up that vacuum line and was clogged in the throttle body. so cleaned throttle body and cleared passageways. replaced vacuum lines.

There is no EGR valve as it has aftermarket exhaust. never had an issue with that for the 4 years ive had it.

if i start it with the pedal floored and clear out the flooding i can drive it 2 footed, it loves to go, hates to stop. any suggestions as to where to go from here?

Also it will idle perfectly if i let the throttle down slow after clearing out the flooding. but even after idling for half hour, if i even touch the throttle, or put in gear, it sucks air and stalls

 

Sounds like it lost the ECM ground or the Injector Grounds?????.... How did you default the O2 Sensor to work the fuel trim??????
Sounds like all it knows now is "O2's say I'm Lean... More Fuel!!"

 

grounds are good, tested by using a nice hight beam bulb to put a load in the ground cable with the ecm disconnected.

"How did you default the O2 Sensor to work the fuel trim??????"

im not sure what you mean by this? i replaced the o2 sensor but it made no difference

 

finally getting a cool night here in GA. its about 55 degrees outside, just tried to start the truck for ***** and giggles and started no problem. revved it up, didnt stall, put in gear, was fine....until it warmed up a bit. as soon as it started warming up it was still in park and in the driveway, i tapped the throttle from idle and it sucked air and died. tried to start again and no go, just rolled over and flooded out. plugs are obviously carbon fouled, also have carbon all over my driveway from the exhaust earlier today when i was having to floor the pedal it to get it started

 

so after tearing into it further to see how the intake looked, i realized this has 2 coolant temp sensors. one for guage(which i know is working so i didnt even think about a second one) and a 2nd one for the ECM. its measuring 3.6million ohms and rising. air temp is around 60-70 farenheight. which should be around 10k-11kohms. i have attached the temp and ohms sheet from manual

 

Im down with the ecm coolant temp sensor...

 

Running much better now that the ECM doesnt think its negative 60 degrees Fahrenheit out. I hope this thread helps at least 1 other person out there BEFORE throwing the money i did on it lol

 

Thank's for coming back and reporting on your progress.

 

I agree... Thank You much..... Question.... Was it the ecm coolant sensor or the connector that failed? RedRam?