NCsabi

Well, after multiple checks, parts swaps and general aggravation I am still
stumped as to what is causing my dilemma.
To recap:
Motor starts, (hot or cold) idles fine. If you roll into the throttle you
can accelerate fine, motor runs strong..
If you try to gag it under 3K RPM or so the tac dives to zero and the
engine cuts out and will recover if you hold the pedal stationary or let it
return back to idle, (sometimes) other times it dies with a horrible KNOCK.
Over 3K it does not exhibit this behavior and I can throttle as I like!
This happens whether you are standstill or cruising. All the while, (that
the issue manifest itself) my DME relay clicks wildly.
I have checked for a vacuum leak numerous times. I have swapped the DME
relay with a fresh one, I have replaced the wires and plugs. I have checked
the fuel filter and the pump is new, (summer) FPR and FPD, (just installed)
are also new. I have checked the TPS and AFM over and over and all checks
out fine according to the service specs.
Everything was fine, (daily driver) until I came back from vacation, (the
motor car sat for about seven days) so its not a clogged injector, (new by
the way) or something stupid that you would expect from a long storage
motor..
Oil separator tube is new, fresh head gasket,,, bla bla bla!
I do not suspect the DME simply because the motor runs strong and as it has
in the past.
What the freak can it be!

Nick
87 944S
VA

Steve Lavigne

Sounds like an electrical problem to me. Possibly a bad battery, bad alternator, slipping alternator belt, bad ground, etc...

NCsabi

Thanks for the reply.
Well, the system is fully charged and an electrical fault I doubt would be RPM specific.
I buy it could be a short, but if that where the case it would occur at any RPM or heavy bump.
This issue only appears when blipping the throttle under 3K RPM.
ncsabi@imagemax.com

Rob

Have you checked your fuel pressure?

Rob

NCsabi

Thanks for replying.
No I have not.
I am going on the assumption that with a new fuel pump, FPR and FPD and that the motor runs strong under a load (3K to 7K) with no issues or starvation. Therefore I eliminated it as a possibility.
It is my impression that the motor is using much more fuel at high RPM than at idle, plus it does not correlate to the wacky DME relay clicking, (during its little episode when trying to blip the throttle).

SoCal Driver

Factory alarm.

NCsabi

Thanks for the suggestion.
How do I go about testing/disabling?

SoCal Driver

Pull the plug on the alarm unit and jumper 4 to 6 and 7 to 8.

4 to 6 is the break in the primary coil of the DME relay.

Another recent thread mentioned that the drivers door switch needed cleaning as they were having alarm activation problems.

Danno

"I have checked the TPS and AFM over and over and all checks out fine according to the service specs."

By this do you mean you've check the output voltage through the entire sweep of the TPS and AFM? The voltage should rise from 0.25v to 4.60v on the AFM smoothly without any sudden drops or jumps? The TPS should go from 0.50v to 3.75v smoothly as well?

The clicking DME relay is a clue! This sounds like the activation signal to the relay may be sporadic. I suspect the alarm box. You can try bypassing it completely.

I was talking to another guy that had a similar problem. Found out that his alarm fox was FULL OF WATER !!! A rotted out battery box had leaked water down the harness wires into the alarm box...

SoCal Driver

The TPS is the two switch type for the 87 "S" model.

NCsabi

Thanks for the help, im chasing down the wiring diagram now.
I see that it is located in the passenger foot well, I have been in there but I don’t recall seeing another control box.
Where is it located in relation to the DME control unit?
And SoCal Driver is right about the TPS, just off stop and just before WOT on the S.
Thanks again.

NCsabi

Oh,, and I did check the AFM.
Nice smooth progression of voltage with no binding or stickiness

SoCal Driver

The turbos do have a closed throttle switch but a resistor for the travel. As I haven't bought a 951 I can only guess what this is for.

Danno

Whoops, sorry forgot we weren't talking about a Turbo.

"I see that it is located in the passenger foot well, I have been in there but I don’t recall seeing another control box."

If you're refering to the alarm box, it's usually clipped to the back of the DME bracket. About the size of a pack of cigarettes.

NCsabi

I bypassed the alarm box. The issue is still there.
Im going to check all the sensors through the DME again tomorrow. I have to be missing something.
Thanks for the help

Nick
87 944S
VA