Need help if someone can

[ep-80]

Ok i have a 92 blazer 5.7, i cant get this truck to run right at all anymore, its been running like crap for the past few months. What it is doing is, the idle is droping down to where it almost dies then comes back up. i was once in a parking lot just started it up went to put it into gear and it died. (If you need more info on what it is doing let me know) What i have replaced, ignition module, coil, spark plugs, rotor, cap, SP wires, O2, there is no air leaks. what is dont to it is- It is chiped, no CAT, 40's flowmaster, no headers, TBI spacer, and stock intake but K&N in it. I just dont get it anymore. It use to run great with no problems. I just really tired of it but dont want to give up. It is the only thing i have to get to work and back so i do need this to run right. I hope some one can help me, thank you.
-Greg

Oh BTW i have replaced the fuel pump and filter forgot to add that sorry.

 

[DriverSideImpact]

Look around for a vacuum leak. Sounds like leak symptoms.

 

[ep-80]

i had it in a shop a few days ago and they could not find any

 

[BHBurban]

What's your fuel pressure?

 

[ep-80]

i have not checked it latey cause i installed the new fuel pump a month ago, but things i do know can crap out in less time then that

 

[DriverSideImpact]

Well he said he replaced the fuel pump and filter... so I'd assume PSI is good. Umm how about fuel injector? could be dripping or kinda clogged or just worn out.

Any other symptoms? Does it do it all the time? Just in park/neutral or does it do it in gear? Hesitate? Fuel mileage?

 

[ep-80]

it does it only in gear when it has a lower rpm, it has been doing it all the time now, i have not checked the fuel mileage cause i have over size tires so the everything is off. The TBI has never been gone threw, only ran injector cleaner threw it. it is a newer engine , i got it new. It might have a good 50k to 60k on it now.

 

[DriverSideImpact]

It does the high and low RPM thing only in drive?

And 60k on the injectors...its probably time to at least have them cleaned.

 

[ep-80]

yes only in drive when i stoped, when it has a low rpm. well the TBI prob has over 200k on it, and like i said i have only ran injector cleaner threw it, never took it off and clean it or re built it.

 

[Bigg G]

No cats and chipped........gotta wonder if it ever did get a good tune.

Back track trying to pinpoint what was done or changed when the problems started.
Is the ECU throwing any codes ?
Have you had it scanned ?
Have you had the I.A.C. tested ?
When you changed the fuel pump did you install a new fuel filter ?

GMT 400 OB1's are normally pretty easy to diagnose & fix.