Fuel Supply Problems

[Dangerous Dan]

1984 944 N/A with a five speed, 58,000 miles and is in pretty good shape generally. However, I’ve got some fuel supply issues that I haven’t been able to figure out. The primary one is that the engine hunts for a stable idle. When the engine is warm and I’ve driven 15 miles or more, I’ll throw in the clutch to stop at a stop sign or park in the parking lot. The engine revs drop to about 800 and then they go up to 1500 and it justkeeps cycling up and down between 800 and 1500 rpm. The only way I can stop it is to slip the clutch while the brake is on to put a load on the engine. This problem occurs when the air temperature is below 35 degrees.
When the car is idling “normally” in warmer weather the revs go up and down rhythmically about 100 rpm.

Also, in colder weather while driving at 2400 rpm in 5th gear with cruise control, the engine was hunting plus or minus 100 rpm on flat or slightly down gradient stretches of road. It settled down while going up hill with a load on the engine. After traveling about 50 miles this way, I pulled off onto an exit and stopped. The engine then began to run very rough and would barely idle; about 600 rpm. I sat there for about 10 minutes trying to figure out what was wrong and all of a sudden the rpms went up to 1100 and the engine smoothed out. On the way home the same day on the same stretch of road at the same speed with cruise on, it was steady as a rock.

Now that the weather is warmer, I haven't had the above problems, except for the idle changing 100 rpm. However, last week I had the following problem, which I think is related:

I round a tight corner doing about 45 mph. On the exit I press down the accelarator pedal and the engine stumbles. I let up and it smooths out; press down 1/2 way it stumbles; press down just a little and it runs smooth and slowly accelerates. I stop at a stop sign and the motor will barely idle and runs very rough, so I keep the revs up. The problem persists for another 3 or 4 miles and goes away.

Any ideas?

[bluebullet]

sounds like maybe your idle air stabilizer valve might be getting stuck.

The severe idle hunting I hear is a problem with early 944 models, the wilks chip cures it. Fuel filter might need changing, and if it has 58k on it and it hasnt been changed yet, now is the time to do so. Check your plugs, wires, cap and rotor for the stumbling part at light throttle, and your AFM might have a dead spot as well. Youd have to pull it apart and check it out. Search around on here, there are a couple of topics related to it.