rocket951

I was driving my '88 951 on the interstate today for the first time and when I tried to pull off a couple of quick passes I experienced a major stumble from the engine. For example, I was in fourth gear cruising at 55mph and rolled on the throttle and quickly jumped up to about 70mph but at that point it just stopped accelerating and started bucking and lurching. I backed off the throttle ever so slightly and it smoothed out. I could then gradually work up to 70-75 but it happened again later as I was gradually accelerating. It seemed like a fuel delivery issue although I couldn't be sure.

Does anyone have ideas as to where I could start looking to form my diagnosis? The car seems to run great aside from the trouble this morning. This is my first 951 and I have only had it a week, TIA for any suggestions.

Rodney

OriginalSterm

O2 sensor

rhesus

o2 sensor isn't used at WOT

Russ Murphy

What's the boost pressure look like? How high is it going and is it rising smoothly?

Peckster

Clogged fuel filter? It's a cheap to replace.

Jason_86_951

Sounds like overboosting to me.
Check to see if the line going to your wastegate is ok.

Mike B

I would agree with the over boost protection kicking in. My car does the same thing since I added the Lindsey wastegate and Avcr EBC. When I'm in fourth and accelarate it shuts down as you describe.

I have the stock chips but will be replacing them in the next few days. Just in time for winter

rocket951

The boost read about 1.5 bar on the gauge and acceleration was very smooth up until that point. I did notice that this problem does not occur at slower speeds in lower gears, like hard acceleration in first through third. It seemed like it only happened during a roll-on situation.

Thanks for everyones input!

Rodney

dand86951

How long since you looked at your spark plugs? Take them out and look to see if you have any unusually large gaps or if it looks like you are running too rich or too lean. How about wires and distributor rotor.? If any of these are bad you could have this problem.

reno928s

I had a problem similiar to yours, as I was driving on the interstate the car would hesitate unless I gradually increased my speed. In the begining it did not happen all the time. Then one day the car could not hold a steady speed, each time it was less and less until it completely cut out. Tune in tomorrow, just kidding, it turned out to be my fuel pump. Reno

cpt_koolbeenz

Hmmm... It does sound like overboost though... I had that happen to me - I could get it to do it in 3rd going WOT up a hill. After it happens the first time, the DME goes on a "safe mode" till you shut off you engine. That could explain why it does it easier after that. In higher gears 3-5, the car has more load and causes the turbo to carge the input air more. Check your CV (if its stock) valve. Is it stock??

Stefan

Sounds too good to be true, but I had a very similar problem and to make it worse, it was intermittent. After checking vacuum lines and all kind of stuff, I eventually found 1 of my spark plugs had a loose electrode that would slide up and down inside the plug totally changing the gap.

TAKE A CLOSE LOOK AT THE PLUGS. It's an easy check.

ehall

http://www.clarks-garage.com/ It never hurts to check this site first. Rather than go high tech/ complicated, start with your fuel filter. I had the same symptoms caused by an old clogged fuel filter. Our cars seem to go through fuel filters a little more often than seems normal for other cars. People told me all of the things you've read above, and I luckily started with the fuel filter for 20.00 at Paragon, and the DME relay. I didn't need the relay, just the filter. It was instantly fixed. Keep in mind that some of these guys have spent big bucks on mods , and tend to knee jerk to the more "sophisticated" prob/solution. That's not to be an insult, it's just part of the techie make up. Try simple and cheap first. If its not the filter, it will be soon enough so you may as well change it. Goodluck. Check out the CLark's garage site. It is INVALUABLE!

Luke

vac leak, Make sure your IC pipes are on there good

Stefan

GREAT SITE! Thanks for the tip.

I definitely agree ... start simple. I was suspecting all kinds of things from DME computers to various vacuum lines.