M758

I have an 84 944 that is running rich. I noticed by a rough idle with a bit of roll between 900-1000 rpm when warm. It is just rough when cold. I pulled the O2 sensor wire and it ran much rougher with occasional puffs of black smoke out the tail pipe. I plugged the O2 back in black puffs when away. When I pulled the plugs I found them completely black. The car had been sitting for some time and I though the injectors might be leaking. I pulled them and found them very dirty. I had the injectors clean and serviced. They appeared to be good on initial testing.

I have not installed these back in the car yet and was considering that they might not be the issues. So what next? It looks like I have an overfueling situation. Could it be a bad FPR? I have checked for vacuum leasks, but everything seems fine. Also would not a vacuum leak cause more AIR and lean condition?

Should I check AFM? What else?

Thanks Guys!

Mike S

I'm not sure if this applies to the NA's as well...but on a turbo a vacuum leak will cause a rich condition like you're describing. Since they're aren't as many lines on the NA it wouldn't be too tough or expensive to replace those rubber lines if you haven't already.

Kevin Baker

Check the FPD it has failed if there is fuel on the vacuum side. Before you throw $$$$ at it check a little temperature sender that is under you injection boot. Blue insulation, three wires, sends engine temp to the DME. $37 versus $70 for FPD.

M758

Kevin,
The blue plug temp sensor. Can I test it on the car (check for voltage/resistance) or do I need to replace it?

nine-44

If you need the dampener, let me know man. To check it, start the car and pull the vaccume line off of the FPD. If bad, it should spirt fuel. Be careful not to start a fire man! I'd do that firt, alot less involved and I'd say it would be the most likely for the symptoms.

944Play

There is also the air temp sensor in the AFM....

These temperature = impedance charts ruthlessly stolen from Danno's postings, but he probably just got them from the FSM. DME water temp sensor (NTC II):
32F = 4.4-6.8k ohms
59-86F = 1.4-3.6k ohms
104F = 1.0-1.3k ohms
176F = 250-390 ohms
212F - 160-210 ohms

DME air temp sensor in AFM (NTC I, I guess. This is probably for a 951 so could be different):
32F = 4.4-68k ohms
59-86F = 1.4-3.6k ohms
104F = 1.0-1.3k ohms

Charlotte944

I had a similar issue with my '87. Car ran rough, used too much gas, plugs were black, cold idle was awfull.

I did all kinds of testing (fuel pressure, vacuum, temp sensors, ad nauseum), and nothing worked.

Finally I had a revelation and decided to check the Fuel Quality Switch in the DME. Turns out the switch was set to 3% rich. Set the switch fully CCW (stock setting), and the problem went away.

For more info check here: http://frwilk.com/944dme/ Click on Fuel Quality Switch in the left frame....

M758

Ok,
I have not had the chance to check the car out, but it here is my plan.

Things to do.

1) Put injectors back in & test engine
if still not good...
2) Check DME switch
if it checks good
3) Check Blue block temp switch to specs listed
if it checks ok
4) Check FPD (see if it leaks)
if it checks
5) Check Air Temp signal from AFM (check to specs)
if it checks good
6) Vacuum Lines??
if they check good
7) anything else?


Thanks

sm

Kevin, et al:

If the temp. sender fails, will the temp. gauge on the dash show funky temperatures?

My engine oil stinks of gas after only 80 miles of driving and this has been changed/checked:

FPR (2.5 bar - stock)
FPD
Resealed Injectors (checked for leaks - negative)
O2 sensor
FQS - full CCW

The next item is the temp. sender, but how will a bad one affect the gauge needle and A/F ratio?

Thanks!

JoeyMac

I vote buy a Apexi S-AFC, then dyno tune it.

MHT

temp sensor has no effect on gauge, that signal comes from a different sensor, have seen several problems with the connectors at the coolant temp sensor, try wiggling the connector and see if the engine responds. A vacuum leak in a non turbo car will not make it run rich, it will run lean. The FPR can stick and cause a very rich condition, it sends fuel pressure sky high when it does, the diaphram in the regulator or damper can fail and pump fuel through the vacuum line. A remote possibility is a flooded carbon canister and faulty purge system, try disconnecting the hose to the canister, the braided hose near the brake booster, and let it suck fresh air and see if that has any effect.

M758

Well I installed the clean injectors. I checked the FPR & FPD by blowing/sucking (no jokes please ) on them to test for ruptured diaphrams. They both seemed ok.

I also tested the block temp plug and afm temp sensor. Both appeared to be operating in the normal range of resistance.

DME FQS was untouched and good.

So I cleaned the plugs with some carb cleaner and put everything back together.

Car ran fine. Cold idle was about 1000 rpm, Warm idle was about 900 to 950 and steady. Gas milage gage showed 40 mpg on warm idle when before it showed abotu 22 mpg.

Looks like my problem was injectors not working right. I do plan on installing new plugs very soon.

Thanks guys!

AndyK

Hey Cliff-

Where is the DME fuel quality switch located?? I wonder if mine is set to run rich?

Rich Sandor

Heh.. I saw the post title:

"Causes for Rich Running"

and I thought, hell, a lotta things will make me run... snakes, rats, fat ugly women...