[mad hooker]

Ok its a 92 gmc 350 tbi engine. The truck starts up fine and idles good. When I drop in in drive its fine but as soon as I give it a little gas, say to go 5-15mph its stumbles really bad and dies. I thought it might be a vacuum leak, so I checked my wires and connections, and everything looks good. The engine never died before, until last night, so know I'm thinking it could be a fuel problem. Maybe a clogged filter? The truck does have just over 200,000 miles on it and I don't know if they were ever changed in this time. Is there anything I can check to be sure its not the tbi unit? Everything looks good and clean and the throttle plates look good as well. I'm really trying to hunt this demon down. Thanks everybody. :thumbsup:

 

[texasgilbert]

I'd check the fuel filter first and go from there.

 

[bbm]

Fuel filter first then the regulator, also hook up your timing light and use it to look at the spray pattern of your injectors with the air cleaner and spacer removed should have same pattern on both fanning out.

 

[wotr]

Fuel filter

Module in distributor

Fuel pump,, in gas tank. LJ

 

[mad hooker]

ok guys did some work on the engine, and it still does the same thing , stumbles really bad and dies. ii have changed the fuel regulator, fuel filter, distributor module and the in-tank sending unit. the fuse for the fuel pump and fuel relay are both good. could it be the pugs? i checked a couple and it seems the be running rich.( the plugs i checked were black) what else could it be? thanks guys. :sad:

 

[wotr]

Throttle Position Sensor,,,, Sounds just like a carbed engine when you give it gas and the throttle blades open ,,gets too much air and not enough fuel, or the timing does not advance with rpms.


I'm sure you checked Cap, rotor,, etc;

Getting any codes?

Before you spend too much money just replacing things, you might want to get someone to take a look at it. LJ

 

[chvyscott67]

does the tbi have a i.a.c !!

 

[engineguy]

I agree with LJ, throttle position sensor. Fuel injection is very sensitive and there are many sensors and relays involved. I would have someone check it out who is familiar with f.i. Otherwise you will spend a ton of money changing things and may never find the culprit.

 

[OLDED]

99% sure it will be the TPS - it regulates the air/fuel, or at least sends the signals to control the ratio. Seems also that symptoms will vary from car to car.

 

[mad hooker]

well after trying to find out the problem throught the fuel system, i starting looking at the IAC (intake air censor) TPS and the MAP sensor. replaced all three from junk yard parts only to find the problem was still there. thank god i pulled a few extras of each because i was ready to call it quits after the problem was still there, when my girlfriend urged me to try the other extra sensors that we picked up.Well why the hell not, it wont hurt, so i changed the IAC again, and sure enough the problem is fixed! no more stumbling or hesitation. :hurray: thank god for girlfriends.:thumbsup:

 

[chvyscott67]

does the tbi have a i.a.c !!

and me !! just kidding, glad u figured it out, my buick 3100 had almost the same problem !!

 

[mad hooker]

the problem came back.

it ran great for a couple days.
today i changed the spark plugs (colder plugs) & the hesitation/stumbling came back. it dies right after hitting the gas at all.


what could be the issue?!

 

[mad hooker]

well i finally found the problem. its the little vacuum line that hooks up to my EGR valve. when its unhooked it runs great no stumbling or hesitation, when it is plugged in, and i hit the gas it stumbles and dies. so does that mean my EGR valve is really dirty? i would think with the line unplugged it would be a huge vacuum leak, but it runs awesome with it off and crappy with it on........ so should i change my EGR valve?

 

[bigdogD12cat]

I know what is wrong , you have an open or grounded
loop.
a few things will cause this
1- plug wires to close to coil or dist.
2- bad wire from computer to everywhere.


how to fix:
you will need volt and ohm testers and check
1 wire at a time till you find the little s.o.b


I just went through this ,I bought everything
just like you, plus went and bought autoxray
scan tool,it said (open or grounded loop)
anyway started at computer (about 100 wires)
and finally found a bad one, it was brown in
color but that was the problem.
Only took me 3 weeks but it runs great now

hope this helps, know its not going to be fun
but it is cheaper than shop rates.
good luck!
Ray

 

[ironhead]

well i finally found the problem. its the little vacuum line that hooks up to my EGR valve. when its unhooked it runs great no stumbling or hesitation, when it is plugged in, and i hit the gas it stumbles and dies. so does that mean my EGR valve is really dirty? i would think with the line unplugged it would be a huge vacuum leak, but it runs awesome with it off and crappy with it on........ so should i change my EGR valve?

The egr valve has an internal spring that weakens and allows the valve to open to rapidly at low rpm.replacing the valve is necessary.
You could sacrifice the small vac line by drilling a few holes in it for testing purpose.This will bleed off some vac signal and the current valve would roll open slower.don't worry about the tiny vac leak you created for testing..the ecu will adjust the fuel and iac to compensate.

 

[mad hooker]

when i have the vacuum line disconnected from the EGR valve the truck runs great. so the EGR valve is opening too fast?