BretD 88GTA

A couple times recently my car has had a bad stumble when it's fired up for the first time for the day. It idles fine, it's when I go to drive off that the stumble occurs. The engine will miss, barley accelerate, and I get a popping sound out of the tail pipes. This seems to be taking place while the ECM is still in Open Loop.

It did it again this morning and I could clearly tell when the ECM went to Closed Loop. There was a noticeable change in the how the car ran and the stumbling cleared up.

Also, I have noticed that my car will develop a stumble after sitting in stop-and-go traffic for a while. When I go to accelerate the engine will hesitate briefly. My A/F ratio gauge will also indicate a rich O2 reading when the stumble occurs.

Anyone have this happen before? I want to try to pin down what the source of the trouble is. I'm thinking there's either some type of fuel problem, or worse, the engine is developing an internal mechanical problem.

james_85Z28

awe c'mon. I'm almost done with my suspension mods and here you are already complaining your car isn't running right. I want to get you out of the way before I demystify, consume and discard the horsepower-challenged RedRocket
There can be only 1 !

Hook up a scanner to check what the TPS and MAF sensors are reporting. Sounds more like a sensor problem than a constant mechanical problem.

BretD 88GTA

No SES light has come on, but I'll bust out the Auto X-ray and see if anything is outta whack.

injdinjn

Don't know if this will help, but I will pass it on anyway.
It isn't a TPI, but my 94 Chev van has poor acceleration mostly after a gas fill up. A friend that was a GM (corp not dealership) customer rep asked a few service mgrs and they said to check out the charcol cannister. It could be full or not operating properly.
I never checked out the cannister as I have never found a way to get to it.

BretD 88GTA

So far this is actually occuring on my car when the tank is getting low - 1/4 or less. I filled it up later on Saturday and it ran beautifully on Sunday. I like James' suggestion of a sensor acting up, but without an SES light indication, it's tough to say for sure that's what it is.

I'm also going to inspect the fuel lines. Mike's car was doing something similar when his fuel tank got low and it turned out he had a damaged fuel ine.

james_85Z28

when my MAF and TPS went out in my car I never got a check engine light and no codes were stored. The 165 ECM is a dumb ECM.

BretD 88GTA

A bad MAF should set a code 33. The TPS won't set a code if it's acting up.

demonchild

i know i shouldnt say this from fear of being flamed, but when is the last time the plugs were changed. my car did the same thing when the plugs were fouled.

BretD 88GTA

Plugs were changed just recently - Bosch Platinum 2's - so it's not likely, but that's not a bad suggestion. I haven't checked the car out yet, but it couldn't hurt to pull a plug and inspect it to get an idea of what's going on in the engine.

james_85Z28

Should and does are two different things. Unplug you knock sensor and see if you cheack engine light comes on. It should but probably won't. A bad MAF would set other codes before it actually set it's own. When my MAF went bad, when it did set a code, it set the EST code, not the maf. You are being too logical. You need to think like a monkey in order to understand the GM engineers.

12secSS

langss

I'm supposed to be having the "Bird" decal installed this coming saturday morning(I'm not holding my breath), but that should not take more than a couple of hours(the shop is only open 9-12) so if you would like I can come buy with the Scanner and you can try it out from first start up and see whats doing what.

BretD 88GTA

Lang,
What scanner do you have? I have an Actron/Sunpro and a new Auto X-ray unit. I just need to pick up the OBD I cable for the Auto X-ray since it only came with an OBD II cable, which works great on my '96 Cadillac.

langss

SnapOn

BretD 88GTA

(insert Homer Simspon voice over) Mmmmmmmmm Snap-on. (insert drool here)

I may have to take you up on your offer.

langss

Just let me know.

BretD 88GTA

Well, Lang came by today and we hooked up his Snap-On scanner. The car showed no signs of a problem and all the readings were within perameters. I guess I just had a fluke stumble due to a dirty spark plug or something.

demonchild

ya i tell everyone to change the sparkplugs now, but i dont tell them to do it theirselves. read my post about 2 months ago...i changed them. the stumble siezed and my gas milage went up like 5 mpg. the only thing is it took me 3-4 hours. i hope the next time i go to change them, it goes a little faster. at least it better, or im getting someone else to do them in the future. i swear changing the plugs was more diffucult than when me and leo037 removed the damn engine from my car.