Ben951S

*editing to update*
Hi RL. It's time. My car is back from the shop. Said the AFM was showing 15% out of spec. I replaced it with a known good from lart. Ran into the no start issue again.

89 944 Turbo.

Put in an A-Tune. Running 2.5bar fpr (will put the 3.0bar back in but it seems fine on the 2.5bar...)

Fuel pressure - Have a gauge on it, looks good, holds pressure
FPR or dampener - FPR was a new 3.0bar Bosche, now it's a 2.5, still rich. Dampener not checked.
Injectors - Not leaking, original. Removed plugs and replugged in, seem fine
AFM - Replaced with known good
Coolant temp - Replaced the DME Temp sensor, wiring seemed ok (did not make a crispy sound when moving it)
FQS switch - set to 0
O2 sensor - Is this looked at during a cold start? Is working as I am 14.7 at idle...
Vacuum/boost leaks - Nothing found with smoke machine. Low vacuum during startup, but car has a street cam so this I am told is to blame (~8psi, warms up to ~14psi)
Weak ignition system (can cause false WBO2 readings due to misfire /incomplete burn) - New spark plugs, not too many miles on the other stuff but can look into...
DME chip (although unlikely, it is possible to get a bad burn) - Maybe?
Grounds - Grounds look good according to experienced tech looking the car over.

I just don't know where to look now. We're talking <10.1 at start up, and it gets into the 11s (maybe a hair higher but did not discuss/has yet to be tested) on driving.

What would be telling the car to run rich, all the time?

Fara

If it's at a shop, have they used an O2 sensor at the exhaust pipe to measure your stoichiometric ratio?
if yes, what's it at?

Ben951S

They used my WBO2. I mean, the car is so rich it coats the back (white) and you can just smell it. WBO2 says <10.1 and I believe he said gets into the 11s once temp starts to climb. They had yet to road test it.

seafeye

Dirty or blocked air filter?
Wrong spark plugs?
What altitude are you at? Could the alt sensor not be working? Force the circuit closed. Does that help?

Fara

That is properly rich.

Our engines run on Open loop mode (without the o2 sensor) till the engine is up to operating temp.
They only switch to closed loop (using the o2 sensor) once they are at temp and if they detect an O2 sensor is connected.

while the engine is running in open loop mode, they base the fuel injection on the amount of airflow into the engine using set tables. It's extremely unlikely that these tables are your problem as they are stored on the DME Chip and you tried your stock chip as well.

Therefore, the next probable check is your AFM.
Are the contacts clean and have you got the tracking on it as per Clarks Garage?
If the AFM is reporting a lower throughput of air than the engine is actually getting, it will cause this problem. Not particularly likely, but possible.

Ben951S

Spark plugs are correct Bosche WD... I forget but what the car had before and some 944 online places sell.

Altitude is east coast, so low. I didn't think 89 had that.


AFM is original, and I do not believe has been checked. I can see if they have a spare to swap or to run a meter on it. Thank you.

ZR8ED

symptoms of "Too rich" can mean a couple of things:

1 Too much fuel delivery (pressure, dampner leaky inj, incorrect dme signals)
2 not enough air getting in (blocked passage, or afm telling the dme more air than actual is getting in)
3 loss of compression (compression test)
4 weak spark (coil/plugs/wires/timing off)

11:1 is way rich..pretty rich for WOT even.
Pick off the easy stuff first.
Does it get air (includes signals to dme regarding air and temp)?

Ben951S

I fwd'd the info from this thread and my search. Anything else fellas? I will post the results once we figure it out. I'm just bummed out because I want my car sorted and I'm tired.

gtroth

Engine temp sensor (NTC II) reading wrong?
Might be telling DME that engine is cold and to run cold enrichment.
Air temp sensor (NTC I in the AFM) might be lying and telling the DME that the air is colder than it is (denser so needs more fuel).
AFM itself has been known to lie too telling DME that more fuel is needed to go with the amount of air it thinks it's reading. I'd verify AFM is right first.

Ben951S

..

KuHL 951

Something else to check. I had a constant richness issue on my 86 951. I replaced the O2, the cat, cleaned everything, checked all sensors and it still ran rich. It turned out to be the AFM door had a weak return spring and would open too wide telling the DME to add more fuel to counter the 'added' air that wasn't really there. I swapped out to a spare I had and it passed smog better than the entire 7 years I owned it. The AFM door should snap shut, close fully with some authority, and take some pressure to move; mine could move by just blowing on it.

Ben951S

What's the best way to replace the AFM (source)? Just take a shot with a known good from some one parting out a car? So what you're saying is is that even if it meters out correctly if the spring is bunk it could still be the AFM.

KuHL 951

Can you borrow an AFM? The spring pressure is very precise and factory set. It requires a special instrument to calibrate it. The intake draws whatever air it needs to pull that door open to counter spring pressure. When the door moves too easily it lets in too much air, the meter says send more fuel but it will always be rich because it can't burn it all. I'm not sure what you mean by 'meters out' OK unless you are talking about the tracking arm voltage not having dead spots. If you know anyone with a 944 remove the airbox top, and press your finger against the door and compare how it opens and closes to the pressure on yours. My bad one didn't even have the spring pressure to close the door fully resulting in failed smog at idle and it ran rich through the entire rpm band. Maybe mine was just a fluke but it was easy to check.

I'm sure a request for a loaner AFM from other RL'ers would prove helpful. I was lucky to have 2 spares on hand when I found my problem. Good Luck