[SOLVED] 1995 k2500 7.4 TBI running HORRIBLY

[Cuckfield]

The parts you first replaced, do you still have them? If you put them back on and it runs differently you'll have learned something useful at no cost beyond your time. Swap out each individually so you can identify the specific failure point. You would not be the first person to receive new in box parts that are bad.

Did you reconnect the bypass?

I did reconnect the bypass.
And no, I don't. Except for the icm and ignition coil. Ignition coil is a hitachi and icm is acdelco. I haven't cleared my codes by disconnecting my battery, perhaps that 42 is stored from running it at all with the wire unplugged?

It feels like code 32 and 33 are important. Haven't replaced map sensor or egr valve.

 

[scott2093]

I have codes 32, 33, and 42.

you should download your manual.
The driveability and emissions one will be the one to grab...It has the codes and troubleshooting.....
until others jump in...
Got pizza cooking atm....

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[grampadirt]

I replaced the icm with a genuine acdelco, and I replaced the ignition coil. Still running poorly. Any other ideas?

Need to resolve the fuel pressure issue,20psi is too low,our 454s need 26-32psi(per FSM).Remove the EGR valve and clean out any built up carbon from the valve and the intake.I use a screwdriver and a vacuum cleaner.Also while you're doing that check the wiring harness that's next to the EGR valve for melted together wires,had a problem once where that damned valve got so hot it melted a few wires together.

 

[someotherguy]

Yep, 32 and 33 are important..

However, you can have an apparently good-running engine with a code 32, unless the EGR is stuck open, or opening when it shouldn't.

I would address the code 33 ASAP. That's the MAP sensor and they usually don't go bad, but the vacuum connection to them is often suspect at this age. Check the boot where the plastic tube connects at each end but especially at the middle rear of the TBI. If it's cracked, or loose, you'll want to replace that tube with some vacuum line, just be sure you use a length and routing that it won't be prone to kinking.

A bad vacuum signal to the MAP sensor will make it run poorly (too rich.)

Richard

 

[scott2093]

Need to resolve the fuel pressure issue,20psi is too low,our 454s need 26-32psi(per FSM)

rechecked----Has 30psi

post#25

 

[Cuckfield]

Yep, 32 and 33 are important..

However, you can have an apparently good-running engine with a code 32, unless the EGR is stuck open, or opening when it shouldn't.

I would address the code 33 ASAP. That's the MAP sensor and they usually don't go bad, but the vacuum connection to them is often suspect at this age. Check the boot where the plastic tube connects at each end but especially at the middle rear of the TBI. If it's cracked, or loose, you'll want to replace that tube with some vacuum line, just be sure you use a length and routing that it won't be prone to kinking.

A bad vacuum signal to the MAP sensor will make it run poorly (too rich.)

Richard

My tbi vacuum outlet has a plug on it, and the 3 way elbow on my MAF vacuum line has one end going to maf, one end going into engine, and is open and naked in the middle where it would presumably connect to tbi; WTF? Why did the end of my tbi have a rubber plug on the vacuum line?

 

[Cuckfield]

My tbi vacuum outlet has a plug on it, and the 3 way elbow on my MAF vacuum line has one end going to maf, one end going into engine, and is open and naked in the middle where it would presumably connect to tbi; WTF? Why did the end of my tbi have a rubber plug on the vacuum line?

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There's also this line coming from this bolt that goes to nothing, what's up with that?maybe it goes like this, with the tbi one plugged and these 3 all together?

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[scott2093]

Not sure but looks right...
someone with the bb will have to confirm.... I never got along too well with the drawings for some reason

 

[Cuckfield]

This is what it runs like now. Tach is unstable and jumps sometimes, little to no power, wants to die when in gear but doesn't.

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[Cuckfield]

This is what it runs like now. Tach is unstable and jumps sometimes, little to no power, wants to die when in gear but doesn't.

xc_hide_links_from_guests_guests_error_hide_media

I think I figured out what was wrong; one of the harnesses to my two fuel injectors is broken so they don't lock in on the tabs in the injector very well; a careless bump and boom, half of my cylinders aren't getting fuel! Hahahaha. That would do it. Any advice on how to fix the connector that plugs onto the top?