My original post from a few days ago is below. Since then I have verified the functionality of the Main fuel Pump, Tank fuel pump, mass air flow sensor, fuel pressure regulator, and throttle position sensor. Like I said in the earlier post, the fuel pressure relay was recently replaced a while before the problem started. I also attempted to find vacuum leaks using propane , but haven't come up with any yet. Inspection of the connectors for the ignition module and knock sensor were unremarkable. I retorqued the mounting bolts for the ignition module and its heat sink just to make sure.

I spent several hours Saturday reading up on the car then poking around trying to come up with a diagnosis. It seems that the car has several modes of symptoms. Sometimes, it will start and idle indefinetly, but will not take any throttle without stumbling. Somteimes the idle stays up at 1100 rpm, and the car stubles if you stab the gas pedal. Occasionally, it will barely run at all, or will not start. Occassionally, it will strat and drive normally for a few blocks, only to barely make it home running on idle because it won'ttake any throttle. The problems are independent of whether the engine is warm or cold.

I still am not sure what the diagnosis is. I am trying to figure it out before I just start throwing parts into it.

Any suggestions on how to proceed?

Steve C




"Greeting:

Today I had my 945T wagon quit a mile from home after a 5 minute warmup. Efforts to restar about 50 times produced no results. After about 15 min sitting, the car started, but alternatly sputtered, barely running, then would run fine for a bit. Engine felt as if it starving for fuel. Pulled codes, got two: one indicated that the fule pressure was either too low or too high, or that the engine was too rich; the other indicated that there was no signal from the knock sensor. The car has 126K miles, ignition tuneup and fuel filter within the last six months, and has the Bosch system, not Regina. This happened once about 8 months ago, but the problem cleared and has been running great since. How can I proceed to evaluate the problem?
Thanks.

Steve C"

Dear Steve,

Good p.m. and may this find you well. Cost-free, quick things to try:

(a) Wiggle the wire that runs to the RPM/Crank sensor. This sensor sits atop the tranny bell housing, at the 10 o'clock position, when you face the engine. If engine performance varies, when you wiggle the wire, that is a sign of a failing sensor. Usually, when the sensor fails or "goes bad", the engine simply stops. However, if a wire insulation failure is producing an intermittent or weak short to live, it might produce inconsistent engine operation.

The wire runs straight down from a connector on the center of the firewall, just above the engine. The connector is below a harness, covered in a ridged plastic coating.

(b) the constant idle motor might be dirty. It is located on a bracket, next to the intake manifold (driver's side of the engine, US/Canada models). See the FAQs under FEATURES, above, for the cleaning procedure.

(c) the fuel injection relay (radio interference suppression relay) is located in the engine bay, next to the power steering fluid reservoir (for turbo models). This relay should interchange with the cooling fan relay. If the fuel injection relay supplies power to the injectors. If it is failing, fuel delivery to the cylinders will be inadequate, even though the fuel pump, fuel regulator, and throttle are all working 100%. If taking the cooling fan relay and putting it in place of the fuel injection relay produces an improvement, then you've found the problem.

There are other things to check, but you'll need to get "analytical parts", i.e., spare parts that definitely work, even if used.

Hope some of this steers you in the right direction.

Yours faithfully,

spook

Dear Spook,

I believe there's a minor point in your list which might lead to some confusion, where you say, "(c) the fuel injection relay (radio interference suppression relay) is located in the engine bay. . . .".

On my '93 Regina 940 (and on LH too), these are two separate relays. The RS Relay is, as you say, in the engine compartment, and controls power to the injectors.

The FI Relay, probably what Steve meant by "Fuel Pressure relay" (and actually two relays in one case), is mounted in the relay rack behind the fuses.

Just wanted to make sure Steve doesn't miss something or get tripped up on terminology.

I think some of his symptoms might also be AMM related. I'll come back with that if no one else does. He says he's "verified the (AMM) functionality", but how? Meter testing has never been succesful, to my knowledge.

Bruce
--
Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

blocked CAT???, also try changing the plugs/leads/distributor cap & rotor arm...

either it aint getting air, aint gettting gas, aint getting a spark or it cant get rid of the waste...

sounds simple...i know it aint!