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Dumping fuel...

bladwin

bladwin

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My '89 350 just got a new tranny today after being down since sept. + we just got a boat, as you can imagine I'm ready to use it. Here's the problem,

starts/idle's fine, seems to take throttle in P or N ok but when under load it will give a big hesitation and lope just as you give it gas and on the tail end like it's getting to much gas.

I pulled the cleaner and confirmed that it's dumping fuel into the bowl during this frustrating behavior:mad:

Any advice for a tbi newb?

Jason
 
Basics? Plugs, wires, cap/rotor in good shape? Good visual inspection, no vac leaks, etc.?
 
Yea, roger that. Replaced some vac hose that looked bad... problem still there.
 
Thanks for the reply, thought I needed a obd1 scanner. Checked codes, throwing a 33, "MAP sensor signal voltage was too high (low vacuum) for 5 seconds when throttle opening was under 4%".
This describes my problem as it happens when I'm easing out of the driveway.
So it sounds like a vaccum leak?
 
Isn't the check engine light on constantly?

Try removing the ECM fuse for 10 sesconds, put it back in, start the vehicle, and see if the code comes back.

Possible you did fix the problem, but the code is keeping it in "limp" mode. Quick and easy to check.
 
Negative, the light isn't staying on, but I'll disconnect and see what happens.

Thanks!
 
blad nab it!

cleared the code, still doing it... but the 33 hasn't come back yet. My wife and dog are gonna get pissed if I can't get this boat in the water:(

Would this code mean a vaccum leak or the map is bad?
 
Hey Dorian, what about his fuel pressure regulator. Think that might be involved?
 
I guess it could be, if the pump is moving fluid at more pressure than the engine requires and the regulator is bad. Dunno how you test a fuel regulator, can you just remove vacuum and see if the engine runs differently? Make sure the regulator holds vacuum?

TPS is another that ties fuel into throttle, that you can test.
 
If it were a carb I'd say the choke was stuck... I think I've at least figured out what all these little black boxes are on top of my intake.

When pluging the vent on the egr module and giving it throttle at the tb in Park it does the same thing as driving. Lopes along as the injectors rain fuel. ideas? Mabye when I was messing around w/ vac. is when it got the 33...

Thanks
 
EGR shouldn't be coming on at idle, what happens if you disconnect the wiring connector, plug the vacuum line from the intake, and take it for a drive?
 
Changes!

So I unpluged the vac line going from the egr to the diaphram looking thing on the top of the intake (vac regulator?) and it ran fine.......

what does it all mean:eek1:?
 
I think It means you found your problem. The diaphram thing on your manifold is your EGR valve not a vac regulator. If you unplugged the line that goes from the little black box (EGR solonoid) to the EGR valve and it runs fine the little black box( EGR solonoid) is bad and stuck open allowing vacuum to the egr all the time making it open. The MAP sees low vaccum when the throttle opens. ECM thinks you are accelerating at WOT and starts dumping fuel. Thats why the code 33 and excessive fuel problem
EGR should only be open in very light load and highway cruise conditions.
Get a new EGR solonoid should be a cheap easy fix. You can usually find them at auto zone or other autoparts stores. Guenine GM is the best but in a pinch get what you can.
If you cant get the part and you still want to try outthat new boat.You can run your truck with the vac line to the EGR valve unhooked and plugged without harm. Your CEL will come on when you get over 45 MPH with an EGR code. But it wont hurt your engine . All the EGR does is helps fuel economy and emissions at cruise.

EDIT********
The only thing that bothers me is it should have been throwing a code 32 not a 33. But it is possible to set a 33 With EGR fully open to lower the manifold vaccum enough.
If a new EGR solonoid does not fix the problem. The MAP sensor is bad. It is a black box on the right side of the TB near the EGR solonoid with a 3 wire connector and only one vac line going to it. Check the map sensor to make sure the electrical connection is good and the vaccum line is hooked up with no leaks.
Have no fear! You will get your new boat to the lake this weekend:D
 
Last edited:
I'm digging it, bigtime. Thanks so much for the diagnostic time gentlemen!

One step closer to operation, it's been 8 months to long...

need tabs now!
 
Sounds to me like either a vacuum leak or plugged hose at the MAP sensor or a bad MAP sensor.
 
update

So I replaced egr module and the map sensor today w/ delco units and it's still the same problem, crap. I guess I'll double check my hoses...

Mabye leaky manifold?.. I haven't seen anything obvious. Can you have a vac leak somewhere in the TB unit itself?

Hope you all had a good weekend, we got the boat out, just had to use a friends rig... Thanks for the help!
 
more info

So after replacing the MAP and EGR and having the same problem I unplugged the elec connection to the new egr solenoid and the problem is gone again.

So I'm ruling out a manifold leak, anyone have any ideas?
 
Just a wild guess, is it possible the wire to the EGR solenoid is grounding?
 
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