Ok here is my dilemma....

My 98' Suburban with 350 has a nagging "stumble" at about 1500-2000 RPM's while accelerating. I have done tons of stuff to this thing in the last 6 or 8 months and it is not better.....here is a list of the new stuff-

Intake gasket
Plugs-wires-cap-rotor
O2 sensor (one by the manifold)
EGR valve
belt-hoses-flush antifreeze
air filter



It is driving me nuts....anyone have any ideas?

Cosmo

I had the same problem. I would put in a new fuel pump and filter.

Check the fuel filter and pump. Check the timing.

Turns out to be a sporadic misfire on cylinder 6.....shop can't get it to duplicate now....just my luck [img]images/graemlins/wall.gif[/img]

Not trying to 'steal' your post but, I too have the same problem, except that mine's between 800-1500 RPM. I have virtually no excelleration, and dies on me inconsitenly while driving. I've replaced the cap, rotor, plugs, O2 sensor, EGR valve and have re-timed it. Also my Computer spits out codes for lean exhaust, low fuel pump relay voltage, and the EGR valve. Should I be checking the same things as Cosmo? Thanks.

Why not change the #6 injector? It's worth a try. About a $60.00 try.

Yours does sound like a classic EGR valve problem....maybe all clogged up. How long since you changed it?

Lean exhaust.....hmmmm....I wonder if you have bad carbon build up in your intake. I have a hunch that is part of my problem, except it doesn't jive that I only have an issue with one cylinder (although I may have 2 issues)....I know when I did the intake gasket on mine there was LOADS of carbon buildup and mine is a 98....so it stands to reason that yours is even worse on an older rig.

I am also going to check my throttle position sensor....they will give you goofy acceleration when they go bad. It is basically a sliding scale that varies voltage as your throttle input changes. Sometimes a particular spot on the slide goes bad and you end up with hesitations, etc....prolly not going to be my problem but can't hurt to look.

Uh, I don't have a #6 injector. They didn't offer MPFI, '87-'95 were the first and las years for TBI.

Well I did the EGR valve about 3 weeks ago. Also About 5 or 6 weeks ago I sprayed some Valvoline TBI cleaner in the intake and that's when it started running like ****. That and I know for sure this motor [yes it is a used '95 out of a G2500, and yes I swapped all of the sensors] always had cheap gas put in it, and nothing good. I usually run Shell Mid-grade. Also just as I encountered this problem my tach will no longer go above or let the motor get above 2500 RPM. Thanks.

I think he meant my injector....since my #6 cylinder is the one misfiring.

Guess it isn't the EGR then....brand spankin' new....

Sounds like you jarred loose some gunk in there with that cleaner...try a "mexican tuneup"..... [img]images/graemlins/chairfall.gif[/img] maybe it'll cough up what you jarred loose. For info on how to do it....go to the Suzuki/Geo forum and do a search.

Yesterday morning I hopped in the old girl and drove her and it was running terrible....while I was out I picked up a throttle position sensor and slapped that on....this morning it seemed to run fine. So....I am keeping my fingers crossed....hopefully that did it....I'll keep you posted.

Might be a good thing to put on your truck. The part is $25 or $30 at the parts store. Doesn't really jive with your symptoms but even if it doesn't cure your problem it prolly wouldn't hurt to replace anyway.