Overboost problem?
 

I bought an 86 951 (129K miles) two weeks ago and it seems to have an overboost problem, I think. It basically, sputters or cuts fuel when I floor it. If I leave my foot in it it sometimes even backfires. Accelerate slowly and its ok until 1.2 - 1.5 bar of boost or sometimes a little higher. I replaced some vacume fittings and the hose to the wastegate, since these were all dryrotted. I even found ones vacume line that looked like it could be leaking. No luck, car runs the same. Any suggestions, cycling valve maybe? Sorry for the long post.

Well when you overboost and get the fuel cut off it is VERY abrupt. It feels like someone slams on the brakes...is that the feeling? Or is the boost maybe just not working right. If you overboost..you'll know it. Just a thought.

------------------
ßrªÐL£µ
88' 951
2k VW Golf 1.8L TURBO
Reluctantly crouched at the starting line...

Its hard to tell. Sometimes yes it cuts out very hard. Other times it still builds boost but sputters, or misses, or cuts out while doing it. Can the wastegate be opening prematurely, or partially. Sometimes it pops or backfires. Is this what happens when the wastegate opens? Anyone here in the Houston want to take a look at it? It's a little hard for me to tell whats going on as I've never driven one before.

Before getting aftermarket chips though, we need to find out why he's overboosting.

You don't want to find a work around to the problem, you need to fix it first.

Do you have any modifications to your car? Have you done any of these rescently?

You're right PrerYdog. I want to find out whats wrong before any mods. As far as mods go, there are none. I think this car is bone stock/original - right down to the arcing plug wires. I have replaced the wires, cap & rotor(because the rotor broke), a couple of hoses and rubber vacume fittings, hoping to find vacume leaks. No luck yet. Most all the sensors have checked out OK. The best way to describe the problem is that its missing badly at high rpm and whenever I get on the throttle quickly. Getting frustrated. Will change plugs tomorrow, maybe try to swap out a wastegate later....

Had a similar problem in a different car awhile back. Never could find the problem. Sold the car.

Are you loosing voltage as you're getting on it? Maybe your alternator can't keep up. I remember looking at alternators for these thigns a couple months ago, they put out some MAJOR power.