My 951 cuts out around 6100 rpm. While searching for a vacuum leak we noticed that all of the vacuum hoses were extremely hard and brittle. We replaced all (yes ALL) the vacuum hoses and all the rubber parts from the airbox to the throttle body. We still have the same problem. It appears as though the car is overboosting and cutting out. Does anybody have any ideas as to the source of the problem?

Thanks.

 

Is it misfiring?
Plugs, plug wires (are they brittle too?), cap, rotor.

Or is it hitting a brick wall and almost shutting down (overboost protection). What are your boost reading at the time? Are you running a stock chip or modified?

DanD

 

Stock chip, Boost Enhancer, Test pipe. It is the brick wall thing. I have some Huntley Chips that I have not yet installed. I wanted to sort out this problem before I do any other mods.

Justin

 

One more thing. I have only the stock boost gauge and it is reading 2 bar when shut down occurs.

Justin

 

Always at 6100 RPM? Every time? So you can get full boost for a couple thousand RPM before it shuts down, right?

Hmmmm.....
Bad KLR?
Bad cycling valve?
Bad TPS?

Just my .02......

 

Is it possible that the rev limiter is kicking in? I know it's supposed to kick in at 6500, but mine seems to hit around 6400- 6450, and I'm sure it's possible for one to have been set a little low... Of course, if this just started happening, it may not be the case at all, as I'm not sure how it could have been re-set w/out doing it intentionally. It may, however, be possible to change wheels and not get a close enough match to the rolling diameter, which may screw up the tach etc- this MIGHT affect things(?), but I'm not positive...

Good luck
Robby

 

Robby,
Good point on the tires.

sprbxr,
Normally, I would say make sure everything is fixed before you upgrade, but I think the HR chips might fix your problem. Sounds like overboost protection, or possibly rev limiter. I'd throw the chips in, you might have a repair and an upgrade at the same time.

Just my 2cents...
DanD

 

The tach uses the signal from the ignition. If it was based off of the wheels, it would not register any change in revs when you reved with the clutch in while parked.

I second the motion to at least try the chips. I am sure they will take care of your fuel cut.

Dave

 

I'm not completely sure but if it is the over boost protection then you need to turn the car off and then on again to re-set back to normal otherwise it might not be overboost protection.

 

There is now a revised scenario:

Car cuts off at 6100 in 2nd gear
In 3,4, it cuts off (the brick wall) at 5300-5500 rpm. After it does this anytime you create approx. 1.2 on the boost gauge the car hesitates until you let up on the gas pedal.

I installed a VDO boost gauge at the KLR tonight but did not have a chance to get a boost reading. The car has all new vacuum lines and rubber hoses. A test pipe, Boost enhancer (problem experienced w/ or w/o LBE). All new injector seals. Stock air filter and airbox. The car has original fuel regulator, damper and fuel pump. Tomorrow I am going to check fuel pressure.

Would lack of fuel and/or fuel pressure cause the car to abruptly lose power? If it begins to run lean, does the DME or KLR cut the ignition?

Any help would be appreciated?
Justin

 

That sounds EXACTLY like the overnoost fuel cut. The chip should fix it.

Dave

 

Yep, now it sounds like overboost protection. Don't think I would install chips until finding the cause of the problem. I believe (disclaimer-I may be wrong), that the Huntley chips don't have overboost protection, so installing them will cure the symptom of the problem, but the problem will still be there.

 

I think I emailed a mechanic about your problem?

anyway - find a blink tester and get the fault code from the port in front of the fusebox.

Let us know what it says.

 

Do you still have the cat on your car?
Might be clogged -

- yeah, I like that!

still have the cat?

 

Hey!

You said that you replaced all the vacuum hoses, but did you replace the CV (cycling valve)? Sounds like you broke off one of the plastic nipples on the cycling valve (it's plastic and gets really brittle over time due to the heat of the engine). When I refreshed my turbo I just touched the hose going to the CV and it broke right off! Did you also change the hose that goes from the CV to the wastegate? Is the electrical connector tight and clean on the CV?
This is overboost protection cutting in. No doubt about it.
Last thing to check (the most difficult in this list) would be the wastegate itself. The diaphram inside the wastegate can tear and make it basically useless (won't open at all).

good luck!

Dal.
--
'86 951
'90 944S2
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