Please Help!!!

[Proto X]

Ok when I bought the truck it had a little bit of a mis. This weekend I put on MSD plug wires, cap, rotor, coil, changed the plugs and tranny fluid and filter. I also ran some cleaner through the fuel system. It is still missing. No engine light. I don't get it. What else it could be?

 

[gmcturbo]

Re: Misfire

Re: Misfire

you wont get an engine light for missing, thats only OBD2. have you tried a "balance test"? - pulling 1 wire at a time as the engine is running and seeing if one has a different effect than the others.. ex. you pull one wire and the idle doesnt dip, that hole is dead

wouldnt hurt to check timing also.

 

[Bill Z]

Re: Misfire

Re: Misfire

Is the miss fire some poping in the plentum say mostly around 1800 RPM or is it all of the time at any RPM? Does your truck have a stock chip or someone's elses?

 

[Proto X]

Re: Misfire

Re: Misfire

It has a stock chip. Stumbles at idle sometimes it dies. Doesn't seem right at WOT either.

 

[Tooky]

Re: Misfire

Re: Misfire

Have you verified your timing at 0* base advance? The timing had a tremendous effect on my idle quality. Other things that caused my idle to stumble were low fuel pressure, and a corroded Positive battery terminal. Have you run Datamaster on the truck?

 

[Proto X]

Re: Misfire

Re: Misfire

OK so I had someone scan with datamaster this weekend and he said:

"the ecm was pulling out a lot of timing
by the time it hit 14lbs pressure it was down to 4.6 degrees total timing because of knock counts .
i am not sure you i/c pump is working
because the only time i see the intake air temp drop is when you accelerate and the ecm wants a richer mixture "

What do you think?

 

[NecroWolf]

Re: Please Help!!!

false knock possibly, using good gas? real easy to check your intercooler pump just put your hand on the line when it's suppose to be running. iac bad? tps bad? those could cause it to die.

 

[crashing_sux]

Re: Misfire

Re: Misfire

you wont get an engine light for missing, thats only OBD2. have you tried a "balance test"? - pulling 1 wire at a time as the engine is running and seeing if one has a different effect than the others.. ex. you pull one wire and the idle doesnt dip, that hole is dead

wouldnt hurt to check timing also.

Can you actually pull a wire while it's running without shocking yourself? Never been brave enough to try.

 

[GM TURBO]

Re: Misfire

Re: Misfire

Can you actually pull a wire while it's running without shocking yourself? Never been brave enough to try.

Depends on how big your nuts are.

 

[NecroWolf]

Re: Please Help!!!

pair of insulated pliers helps, but the best way i've found to do it is get a buddy :devil:

 

[GM TURBO]

Re: Please Help!!!

pair of insulated pliers helps, but the best way i've found to do it is get a buddy :devil:

Make sure you are the one holding the camera

 

[100in6]

Re: Please Help!!!

look in the intercooler and see if it has any movement. also can check the pump below. wire it to run all the time. putting in a colder thermostat fools the computer into making it a liitle richer. did you put the boots on well if you did it yourself or did the plugs wires come preassembled. do you have an adjustable fuel pressure regulator. do you have a friend with a syty that you could try a different chip. if it misses so bad at idle that it dies and doesn't seem to have any fuel pressure it could also be the fuel pump getting weak.

some things to check