Chevy & GMC Vans

I know most of us have issues with the damp and wet weather with hesitation, missing etc. I have been having problems on my 99 for a couple of months now at least. It did eventually throw one code which I posted about. 'random misfire' that only appeared once when the problem was at it's worst and never has appeared again.

I've changed the cap, rotor, plugs and wires, trans fluid/filter and a fuel filter and the hesitation/ stumbling problem still persists.

I would lean towards a fuel delivery issue if it was at idle as well as under acceleration, at idle it's fine. maybe I'm wrong?

our weather here has been warm and dry for quite awhile now and I finally took the van for over and hour drive, at speed, twice in one day when going to my mothers house last monday.

the problem is still there, it's still as bad. and get this... it's also at highway speed. it happened several times while right around 120kmh (75 mph). under both acceleration and deceleration, right around the same speed. i rarely go on the highway and thought that my under 60kmh (40mph) driving was not helping and I figured the highway long run at speed would smooth things out. it didn't.

I'm not sure how else to describe it other than stumbling, hesitation or lurching. almost like either fuel is being starved for a spilt second or the tranny isn't sure what it wants to do, go don't go, ok go. remember, at idle it's fine, only under throttle is when it occurs... could it be a fuel pressure regulator? if so, where are they located on a 99? lemme guess in or around the tank? LOL

I'm really at a loss and can only think back to it feeling like my dakota 4.7L did when my TPS went bad. yet, I've never heard of you guys talking of TPS problems.

I can't really afford throwing tons of parts at the thing trying to solve the problem (the plugs wires cap and rotor were due) but, I'm not really sure what to do next. the tps ain't cheap, nor is a fuel pump, nor is pretty much anything else. one thing I haven't changed in the ignition equation is the coil.. but again, wouldn't this also cause a rough idle (which i don't have).

i'm totally stumped and just want to get this resolved.... thanks

Do you have an ohmmeter? If not can you borrow one from someone? TPS is easy to check, it's a varible resistor. Resistance should be smooth from closed to open throttle. Or you can measure the voltage from the center to ground. I believe it should be about .6 v at closed throttle and 2.5 v full. I could be off a little going by memory.

yeah.. I do have one. I'll give that a try and see. that's how I diagnosed it on my dakota. i know the dodges have huge (common) problems with bad TPS's ... I've never heard of one going bad from anyone on here before but I supposed based on my description it's worth a check ...

I had a similar cause and effect. Turns out, my 100k plug replacement was with a brand outside of the recommended GM brand. My mechanic, after some troubleshooting, replaced the plugs and wires with OEM and all has been fine since. I would have sworn it was the TPS.

well, I figure that the NGK platinum 3403 plugs are within the recommended GM brand considering the AC delco's platinum 41-993 are made by NGK ... LOL

The first thing I would check is Fuel pressure. You don't need much fuel at idle. At start up you should have 60 lbs or better.

i think i'm going to buy one today

i also found this site which talks about the what's, wherefores, and how-to's

http://www.aa1car.com/library/2003/us60324.htm

it's all a starting point for me anyway.

here's the update. I don't like to admit it but figured it was worthy of updating/sharing..

here's my second post in the seafoam thread that explains the resolution...

yes, a $10 can has cleared up the problems...

Gee Rob,where on earth would YOU find Seafoam,LOL

Glad you got er solved,I can respect the fact you've admitted your ( previous comment re: Seafoam,LOL ) may have been a little on the harsh side

like I said in that post Keith.. I can totally admit if I'm wrong. I really am still with the belief that seafoam isn't the 'all problem solver' that's it's made out to be.. harsh or not.. LOL It just help in this particular case.