So I finally thought my 944 turbo was good to go. I got it out on the track tonight and it's developed a new issue.

Acceleration seems fine on the straights, I brake hard and when I go to get back on the gas for corner exit, nothing. The tach still shows RPM, and if I lightly feather the throttle, the car will backfire mildy, sort of clear it's throat(so to speak) and continue on. The problem got bad enough that it finally lost all power but didn't die. I then drove it 1.5hrs home and stayed out of max boost and zero issues, it ran perfect.

TPS?
FPR?

It feels like lack of fuel but hard to tell. I'm stumped.

 

Do you have AFM or MAF?

 

Is it only in turns after braking, or does it happen while going straight after braking? How much fuel was in the tank at the time? Is it possible that the fuel pump is sucking air because a baffle has broken off or loose in the fuel tank? Does your car have a fuel pressure gauge?

 

Could be a vacuum leak, check hose clamps/condition. My diverter valve hose loosened up on the track causing the car to lose power sporadically as you describe. Luckily we fixed it and were able to finish the track day.

 

Thats a Tough one, The fact that is backfires when it finally "Wakes up" Leads me to Ignition, When the fire comes back its loaded up on fuel and Poof! you get the backfire.. But you really need to Troubleshoot this issue, Hook up a Fuel Pressure Gauge, At least you can confirm its one or the other very easily. Run it out of the hood and Tywrap it to the wiper so you can see whats going on.. once you know if its Fire or fuel, post that and maybe people on here can help further..

 

First off, the car does not have a fuel pressure gauge. Secondly, it does it not matter if I'm going straight or turning. I just replaced all the vacuum hoses, if fact I've replaced every hose under the hood and I went over all the ones I could get to and everything is good.

I agree that it does sound ignition related except that it seems to be induced by very hard braking. The car had 3/4 of a tank of fuel.

I took off the dist. cap and everything looked good. I did find a post online with somebody explaining a similar issue and they said it was the fuel pressure regulator. The diaphragm had torn slightly and created an issue like the one I'm having. It did seem the longer the section, the harder the braking, the worse the problem was, through the left right slower sections it did it but not as bad. Thanks for all the replies so far.

 

Yeah, either too much fuel and lack of spark or too little fuel. One might be able to tell by coming to a hard stop and then rather than turning or getting back on the gas, just stop completely, get out, and smell the tail pipe. If it's a spark issue, you'll smell gas. If it's a lack of fuel, probably no gas smell.

 

Good idea, I will try that.

 

Maybe my idea is flawed - this car might completely cut fuel when the throttle is not used above a certain RPM.

 

What's the recent history of the car...?

Was it wrecked and repaired...?

Is the fuel tank original to the car....?

I would pull the level sender under rear carpet and inspect the stand up plastic column with an LED pen light. Make sure it isn't displaced from the seat.
This plastic piece is like a swirlpot or auxiliary tank with a fuel cell. The pump pulls source directly from there.

Secondly, I would look at the fuel screen at the lower fuel tank that feeds the pump.

Not only does it have to be clear and unobstructed (I have seen a piece of cellophane stuck in there) but the screen has to be fully intact as if a new one because it actually works as a wick to pump suction.

T

 

Car has never been in an accident. It's a very original car in great shape. I don't know 100% but I would say the fuel tank is original.

Some great advice to check those areas. I will start that tomorrow night and report back.
Thanks!

 

Pic of the car:

 

We can only point you in the right direction, actual troubleshooting has to take place, What I meant was that you can get a cheap Fuel pressure Gauge hook it to the fuel Rail (There is a provision for it on our cars) and simply run the hose to the wiper to a simple gauge.. If you start with this simple diagnostic method, you can eliminate 50% of what is Guesswork at this point. (Ignition or fuel) These cars are fairly simple, however some diagnostics and equipment has to be purchased if you want to work on it yourself, other than that you are left with educated guesses, and shotgunning. Perhaps you might know a friend with a gauge? Or a shop willing to let you borrow one? At