sdrake

Hey folks -

Picked up my first 951 last weekend, so I'm a bit of a newbie here. Been wrenching on p-cars my entire adult life, but this is a first front engine turbo car.

Here's the issue - the car cuts completely out under hard acceleration about 80% of the time. It falls dead flat on it's face for a second and comes back to life if you lift on the throttle.

Car is stock with the exception of an auto authority chip and boost banjo.

The previous owner says that this issue appeared well after any upgrades or changes were made to the car.

I have searched all sorts of threads about this issue and it appears that I'm having the symptoms of over-boost, but the car doesn't go into limp mode. (Am I correct that limp mode takes a while to clear? some folks talk about minutes???) my car comes right back to life as soon as I lift on the throttle.

I've seen all sorts of fixes on various threads ranging from DME, TPS, bad coil, vacuum issues and fuel filters... just trying to get some advice since it appears that my car is not going into limp, but simply cutting out for as long as I hold the go peddle down.

Any thoughts or ideas would be greatly appreciated.

Scot

bw993

Do you have a wide band O2 monitor on the car? Sounds like you are running very rich and the stumbling on initiate throttle is a because of too much fuel. Common causes are air leaks after the AFM. Check you inter-cooler hoses. Another issue is to check your fuel pressure regulator to see it is still operating in range.

kyle951

Scot,
I had a similar issue with my 86 944 turbo. My car was completely stock with the exception of the Lindsey boost enhancer. Under WOT and the stock boost gauge reading 2 bar my car would cut out. This was due to the cycling valve and the car going into an over boost protection. My car would never go into limp mode, and would return to normal driving as soon as the boost came down to normal range.

I would be very careful with those auto authority chips because they are known to cause problems with our cars. There are countless threads talking about those chips and some of the problems they can cause. I would suggest a different set of chips or a rogue tune for your car if you are wanting a little more power.

Kyle

SeanR

Encountered this on a 951 and it was the reference sensors.

Jherriott

I had this exact same issue at one time. As soon as boost started it was like someone slammed on the brakes, not fun.

It ended up being a vacuum line disconnected right behind/under the Air-Flow meter box.

lart951

you don't know anything about 951's get out of here

lart951

You are hitting overboost protection, most likely your cycling valve is bad

Northern_aqs

It's not necessarily a defective cycling valve but certainly sounds like the cycling valve is acting as if the car is in overboost protection mode. I've experienced this without a clear cause and would check the simple things that can cause an intermittent over-rich condition first.

1) plugs not fouled, gapped to spec.
2) plug wires with good connection, good condition, no cracks.
3) verify in-spec condition of TPS throughout throttle range.
4) verify no vacuum leaks.

I got to step 3 when I ran into this problem with an intermittently bad TPS.

raleighBahn

I don't know if this will help, but it costs you nothing to try. Drive the car, reproduce the condition, and then without turning it off (codes do not save) connect a blink code reader (see Lindsey Racing tech info) to the test port and see if any codes were captured. Complete list of codes are the turbo workshop manual.

http://www.lindseyracing.com/LR/Parts/BLINKCODE.html

sdrake

Great advice folks - thank you.

Looks like I'm building a blink code reader... never even heard of one. Never thought I would say I miss OBDII ports...

Starting with new plugs and wires since at least the wires look like they have some age. Also ordered a cycling valve... the one on the car looks original

Next is adding a little pressure to the vacuum system and some soapy water to look for obvious leaks.

Scot

odonnell

Soapy water won't really help since you're idling in vacuum.

sdrake

going to pressurize the system with the car off to 8-10 PSI. I've seen multiple posts about this being a good technique, but if I'm about to do something stupid, let me know!

bw993

Best way to look for air leaks is with a smoke test.

Jherriott

Have a smoke while someone else tests it? That's my favorite!

I kid... I kid...

Jase.

sdrake

More like I need to be smoking something while learning the vacuum system on this damn car!