Early 944 running rich - suspects?

[Slam]

My nose is telling me what my MPG gauge is telling me. The car's running rich. FPR and damper seem fine - no fuel in vac lines, plenty of vac pressure on tap. The AFM was refurbished (by me) as per Wilks' tips. Car was tuned up last summer and driven very little since then. I did the fuel filter, plugs, wires, blah, blah, blah.

And yet my MPG gauge stays pegged to the left when I'm cruising on the highway, only to relax when I take my foot off the throttle. I doubt it's wiring, as I put in a secondary grounding harness last summer, too, when I had the dash out.

Car's the 83 944.

Any ideas?

[mikepellegrini]

Maybe the O2 sensor or the temp sensor?

[Marajit]

Did your tune up include the Oxygen Sensor and a check of the ECU Temp sensor?

Also, set the mixture on the AFM.
Lacking the instrument to calibrate it to spec, I've gotten good results by backing out the mixture screw 12 turns.

Then, read the spark plugs.

[Ctan]

I'm aving the same issue. It settled a lot (but is still there) after I checked the spark plugs. Some dumb f*ck put the plugs straight from the package to the head...no gapping. Spec's .028-.031". Mine were set above .06" ( don't know exact...my feelers don't go that high).

But I gapped them to spec and she's running better. Try timing your plugs as well so that the opening of the plug faces the intake valve.

[krystar]

i'm having same problem too. marajit, info on the ECU Temp sensor and the AFM mixture screw?

[Marajit]

Info on testing the temperature sensor can be found here:
http://www.clarks-garage.com/shop-manual/elect-19.htm#dme-temp

Oxygen sensor testing here:
http://www.clarks-garage.com/shop-manual/elect-19.htm#oxygen

As concerns the AFM mixture regulation, the Third World Quantum Mechanic procedure is as follows:

Run engine to operating temperature.
Check the reading of the MPG gauge. It ought to point to 60, often fluctuating to hover briefly over the 0.5 magical numbers on the gauge and back to 60. Turn off engine.
The mixture screw lives in the AFM hole that comes covered with a plug, although I have yet to see one that still has it. Remove if present.
The mixture screw at the bottom of this hole can be a simple slot head screw or a hex.
Screw it in as far as it will go, counting the turns as you do it, then back it out to the original number of turns. This will be the base-line reading. Start the engine.
Back out the screw one turn at a time while observing the behavior of the MPG gauge and stop turning when the gauge reads 60, or close to it.
Theoretically, it will be indicative of the ideal mixture. Turning the regulating screw clockwise will enrichen the mixture, anti-clockwise will lean it.

On my 84 NA, twelve turns of the screw made the gauge read spot on and the plugs to show the correct color.

hth

[Slam]

EXCELLENT info - thanks, guys. I'll run some tests this weekend, regap the plugs and tweak the mixture. Depending on what I find.

[krystar]

i think i have some other problem. i have a wideband o2 installed and even at idle with mixture screw turned all the way out, i'm still at low 13 AF's.

but it's running fine..i'm not complaining too much other than being smelly hehe