I noticed today while cruising at 70 everything was fine....from a stop to seventy or so, with normal acceleration everything was fine. I was playing around and floored it from a dead stop and when it got to 68 -70 it started hesitating, then it picked up smooth, around 90 it started hesitating again. It wasn't a slight hestation, I felt the car jerking!!! It felt like the fuel was getting cut on and off. What could be wrong??????

P.S. '99 SS w/A4. The car did it with the HPP 3 tuning and when I changed it back to stock tuning!

 

sounds like a fuel line problem....might be the pump

 

When's the last time you had a tune-up? I guess first I'd try fuel filter and I'm assuming you're using 91 or 93 octane. If those are both good, I'd probably check plugs and wires next..

Just a few ideas.

 

It's still under warranty so i'm taking it to a dealer today. Hopefully it's nothing major, I'll keep you posted. Thanks!

 

Well took it to the dealer today and after 8 hours at the shop, the Chevy dealer stated, " It's not a miss, we think it is your O2 sensor." Keep in mind it is under warranty, the guy tells me to buy some O2 sims and that should do it! Does this make sense to anyone???? I spent $103 for this guy to tell me this, if he would have replaced the O2 sensor it would have been only $50 charged under the warranty. How can an O2 sensor affect performance, there's no check engine light and the guy says the O2 sensor is telling the computer to run the car lean under heavy acceleration!

 

That is total BS!!! First of all, the rear O2 sensors, which are what you replace with the sims, DO NOT have anything to do with your Air/Fuel Mixture. They are simply there to monitor your Catalytic Converter's function. Second, if you replace your primary O2 sensors with Sims, well, let's just say your car will either stay in Open loop operation, or it will run way rich or lean or not at all. Listen to the guys on this board on this one and check your fuel system first. BTW, I have never driven an A4 Fbody, but is your hesitation happening at the same RPM, especially at near Peak RPM? That would further indicate a fuel problem. That is a starting point, probably go with Ignition checks next. I hate to say it, but you got Ripped by your dealer. I would not stand for that and would take it back or even to another dealer and let them know. A dealer telling you to replace an emission's control device with a nonfunctional one while under warranty has to be one of the craziest things I've ever heard.
I would also consider trying to get in touch with a GM warranty rep over that dealer and try and get your $103 back. Unless you have a good relationship with the dealer, then try and work it out with them.
Good luck, keep us posted.

 

About the RPM's, I checked that. It will hesitate at various rpm's over 3000, only after 3000! That's only under extreme acceleration though, normal driving it does just fine, no hesitation. I took it to another dealer today, he said the other dealer is full of crap. He said he's betting on a bad plug wire, a bad O2 sensor or the PCM. He said he can get to me on Tuesday. Like I said it's still under warranty, I just want my baby performing again. To make matters worse, this morning a black 03-04 Stang GT pulled up next to me and started revving, what could I do? When I get my car running right I'll find that bastard!

P.S. I called the first dealer today and he said, and I quote " You have modified your exhuast and that's mainly what's wrong with the car!!!"

I laughed and said , Dude, you are without a doubt a dip****! So watch out guys if you running anything other than the stock exhaust because the dealer here in hicksville says it will mess your car up!!!!

 

Well, found out what's wrong! The PCM is causing the problem. Does it make sense that my car seems to run stronger without the PP#3 tuning installed??

 

Yes. makes perfect sense. The PP3 tuning works great on bone stock cars, but after modding, you actually pick up power by de-tuning it, dyno proven.

 

So my PP #3 is only good for shift firmness and fan temps basically?

 

yeah. Just use it for like gear ratio changes, tire height changes, etc.