fly89gta

iTrader: (1)

OK, so I'm having this wacky problem that I have yet to figure out. I'll give you some background info.

See the sig for mods. The previous owner did the tuning(years ago)...well the fuel pump finally died a while back. It was the original one so it was probably wasn't even pumping much when the chip was burned. Anyway, replaced it with a Walbro 340 and boy did it wake the car up. But...shortly after install there would be a very slight stumble around 2000-2500 rpm's. I thought nothing of it really. Well, since then it's getting progressively worse, A LOT worse. The car bucks really bad and the wideband shows dead lean. It doesn't matter if it's part throttle or if I'm on it. It's usually around those RPM's.

Now here's the kicker, if it's the first start up of the day it rarely does it...the car runs fine. But lets say I drive it a few miles and shut it off to get something from the store(lets say I'm driving to work). Once I start it back up the bucking and hesitation starts. I'm totally frustrated.

So far the IAC and O2 sensors have been replaced, the TPS read fine....could it be the MAF going out? I know the tune very well could be off now with the proper fuel but the issue has gotten progressively worse which leads me to believe it's not the tune. I'm certainly not super experience in diagnosing these issues but I have seen MAF's on their way out cause this problem. But why would it do it more frequently after the car has been started then shut off then started again? Any input or ideas would be greatly appreciated.

Guest

Get a scan tool hooked up and save a nice long log file. Recently saw a car do something similar with a bad VSS. Otherwise you're kind of shooting in the dark.

fly89gta

iTrader: (1)

Yeah, I have a tech 1 and tech 2 at work but the damn cigarette adapter for them doesn't work.

A VSS eh? Interesting.

Guest

Yea, VSS. I was a bit puzzled myself. Replaced it, problem went away. Go figure.

Those cars are also prone to injector failure, but I noticed you replaced those already so forget that idea. You may want to check the EGR and related parts.

fly89gta

iTrader: (1)

EGR is gone too, blocked off and tuned out of the chip.

I thought maybe it was an O2 so I got one of them(I can get them cheap enough(I work at a Buick dealer)). My next thought was the MAF, I've seen similar problems when the frequencies go all out of whack. I'll have to check on the VSS though. I still might try the MAF, just have to find a known working one. New ones are too much to guess with lol

Still, the VSS I never would have thought.