reference sensor
 

hi,
can someone please tell me what are the downsides when one of the reference sensor are not working properly ? ( i am interested in seeing if it has something to do with fuel consumption as mine is eating ALLOT like 16mpg city driving)

thanks

What makes you suspicious of ref sensors?

one of the sensor is has pretty bad wires

Doubt it would be the cause. Frayed wire may still fuction. Bad wire would cause sensor to not work. Car wouldn't run.

Look at tire pressure, alignment, tune up, etc first

mine are the same way...mine are ripped open. my 944 isnt running. i assume yours isnt either.

mine is running ...i was just wondering what are the problems with a bad reference sensor

hmmm. i don't think your 944 will run with a bad sensor. But I don't know for sure.

then probably it is bad ? ...

its possible to hurt mpg and can prevent starting as well as running rough and intermittent no start, the ecu says:garbage in(signal) garbage out

If the sensors are not functioning properly there can be a multitude of starting and running problems.

Check with Clark's for a complete diagnostic for the sensors...

Clark's Garage Home Page

ok i know how to test it..i did the testing part and what i got isn't like in the manual...but i do not have starting problems...it is true that i feel that the engine isn't running that great..i feel it like it is running very rich...and all the ignition is almost new (coil,distributor cap,rotor,sparks -in good shape-wires -in good shape) ..so this is why i ask what are the symptoms of a bad reference sensor as i didn't find answer .

thank you again for reply's

isn't the speed and reference sensor the same ???

Unusual for a 2.5 to run rich, and unlikely that crank sensors are the culprit. When was your last O2 sensor? Is your FPR operating within spec? Are there any dead spots in your AFM?

fuel consumption
 

IMHO, first make sure the sensor connections are good and solid. Next check the grounds (all of em) and all the FI connectors. If the car is running rich you will be able to smell it in the exhaust and see it on the plugs as fouling. I am leaning towards an O2 sensor or lambda circuit thing. Vac lines, temp sensors and the usual should be double checked. Lastly try testing the MAF.

i do not have O2 sensors...vacuum lines seem to be ok..i do not know about the AFM if it have blank spots or not(i moved the potentiometer arm on different trail)...FPR is a adjustable and i haven'
t seen drop or increase of pressure on the gouge ,could not work properly in load? ...grounds are ok as i have cleaned all of them on the engine (are in other places too??if so where? ) .temperature sensor it was changed not long ago...and yes i sent smell on the exhaust and sparks are black

okey
 

OK then, you have gone over the usual suspects. My apologies for asking a bunch of questions that you have probably asked yourself. there is a tricky ground on the back of the engine that should be checked. Also, the system is voltage sensitive so check for running voltage within specification.

Assuming the signal to the injectors is good as far as voltage and duration (yea, oscilloscope stuff...ugh.) a high fuel pressure will deliver too much fuel. and so the FPR may (or may not) be to blame. There is an an adjustment on the AFM that I warn people not to touch as they can cause more harm than good. I have swapped out AFMs with known good ones for a test.

What are the exact specs on your fuel pressure? and...if it is high...could the return line be crimped, plugged, or deleted? I only ask because I dimly remember a plugged return will cause the same symptoms and render the FPR un- adjustable.

It is looking like a rich running condition and may not be related to the sensors. But, what do i know?

at what system are you referring ?
regarding to the afm i didn't touch the spring (only if it was moved before i bought the car)and i do not have from where to swap with a good known afm (nobody in around with 944 85.5 )
with the injectors i do not know haw is the signal as i dont have a oscilloscope
with the fpr on idle i have 2.5bar i do not know in load what are the readings as i cannot see under the bonnet :)

it is driving me crazy ..:(( ...could it be some electrical problem???i have inspected the DME and nothing seamed to be worn or bad in connections

i had 2 unusual experience - it happen' 2 maybe 3 times when i start the car and it was running very well -didn't felt that is running rich at all-i had very good acceleration respond and felt that engine is working very easy (not like in rich conditions) ...but then after stopping the engine and restarting ,well back to same problem...?!!!

looks like wiring for reference sensor are bad..i have an intermittent wire from the sensor to DME...i have the dash removed for upholstery and i will inspect all the wires.

I would like to ask - are the engine wires specials ? i mean do they have to meet some characteristics(i know they they have to be fire resistant and that they have different thickness) ?

Here is a great tutorial on repairing ref sensor wiring:

Harness Repair- Porsche 951 - www.texasblake.com

if the bad wiring is in an unknown location or not at the end near the connector its ez enough to replace the engine harness with a known good part