Hawk312

iTrader: (8)

I have a strange problem with this car. It is a `99 Trans Am with about 50,000, six speed. It is bone stock. It seems to stumble if giving it more than 1/3 gas in the upper gears at low RPM, between 1500 and 2000 or so. The more gas you give it, the worse it stumbles. However, it pulls really hard in the lower gears all the way up to the redline with no stumbling. It doesnt seem at this point that there is any significant change in gas mileage. As far as I know, nothing has really been touched under the hood. It seems the problem is slowly getting worse.
Thanks

CJDZ24_Z28

iTrader: (75)

My Formula had this SAME EXACT problem. It turned out to be a dirty MAF. Take out your maf and take a look at it. Use Non chlorinated brake parts cleaner and a Q-tip but do not move the push to hard and break the sensors. Also a tune up and new wires would help also.

Cole Train

iTrader: (30)

use ELECTRICAL contact cleaner. Looks like a smaller Brakeleen can. It's safe for MAF and a Qtip but be VERY gentle with it. Also may want to check plugs and wires if the MAF cleaning doesn't work~Cole~

1994Z28Lt1

iTrader: (1)

when was the last tuneup? missing and stumbling at low rpm in high gear is usually ignition related whether that be plugs, wires, or coil packs. If your plugs are stock it might be a good time to do a tuneup anyway. give that a try if the whole MAF bath doesn't work

Cole Train

iTrader: (30)

my '00 V6 hit 50k miles almost to the mile and started doing similar ****. Changed plugs and wires, all was great.~cole~

CJDZ24_Z28

iTrader: (75)

GM actually recommends non chlorinated brake cleaner. I used it on my Vette and Formula and worked like a charm. You could also use MAF cleaner that is sold in most parts store

tspence45

iTrader: (30)

I'm having the exact same problem with my car now, too. I just hope it won't be too expensive to fix. I'm pretty sure that it's the plug wires though. The guy I bought it from did say that it would probably need some new plug wires.

ws6_bandit

iTrader: (5)

Ive had the same problem before.. it turned out one of my plug wires were not fully connected to the spark plug.. good luck

speedshifterNC

iTrader: (1)

if all of those suggestions don't work which they prolly will try the IAC sensor...that was my problem

CJDZ24_Z28

iTrader: (75)

So Hawk is it taken care of or what?

Hawk312

iTrader: (8)

Sorry guys....I`ve been soooo busy lately. I plan to try all the above tomorrow. I`ll let you know the results.
Thanks, everyone, for all the ideas.

1FST-Z

iTrader: (6)

Similar problem here, as well...but not as severe as described in the thread. What I did was picked up a bottle of STP Jet Fuel...actually worked like a charm, no problems since. Guess my injectors were dirty?

tspence45

iTrader: (30)

Yeah, I tried that, and it didn't work. I think I'm going to do a full Seafoam treatment on my car though, since it has about 122k on it anyways. Then, I'll replace the plugs and plug wires. Hopefully that'll do the trick for me.

Hawk312

iTrader: (8)

Ok, I just got back from driving this after cleaning the MAF sensor. I hope this isn`t a stupid question, but do you guys clean the sensors too? I was afraid to touch them with the brake cleaner, as this stuff seems really nasty!
Anyway, I was able to find out that it seems to be worse as the car warms up. I don`t think I noticed it at all while the car was cold. It also seems to be at really low rpms in the top gears (3rd - 6th). If I pull away at 1000rpm in 3rd, it stumbles/shakes/rattles as it does in 4th, 5th, and 6th, up until about 2000rpm, at which time it pulls really hard up until the redline. I checked the plug wires and they seem to all be in.
Any thoughts?

1993camarolt1

I have the same problem right now. I've been having it for a while and can't seem to figure it out. I've changed the plugs, cleaned the MAF, changed both o2 sensors and still the same problem. My car is the automatic lt1 and it drives fine up until about 50mph in 4th where it stumbles. It only stumbles at 1500-2000 rpm then when it picks up you don't feel it anymore. My idle after WOT is also strange. The car idles really low at around 500-600 rpm, and while idling, it seems like it's missing for 3 seconds, then fine for 3, then missing for 3 and fine and so on. The oil pressure/battery voltage also fluctuate as this is happening. This is really starting to get irritating