944 pulsating acceleration

[sts]

My 944 (normally aspirated, 1984) is running OK but not great. When accelerating it seems to lose some power every second or two for just a split second, e.g. "pusating power". I suspect either a timing belt or injector system, but wonder if anyone else has ideas.

Things I have checked and are OK:

Air and fuel filters new

Spark plugs and distributor cap new, all firing

Coil resistances correct

Various sensors in the fuel and ignition system seem nominal

All injectors working (not necessarily perfectly)

[SoCal Driver]

Don't think it's the timing belt. Could be a vacuum leak in the small tubing to the fuel regulator/damper or somewhere in the intake system.

Back to the timing belt; when is the last time it was replaced? These are good for about three years or 30,000 miles.

[nynor]

vacuum leak.

socal: you are the man.

check your belts!!! a kitten will thank you!

[FSAEracer03]

1) Check all the vac lines with a quick visual inspection.
2) Check the injector electrical connections.
3) Check out your AFM connections (electrical contact points and rubber connections - namely the outlet side), especially concerning the intake bellows. With the engine running, knead the intake bellows a little bit, bending it in different shapes and such. If that effects the idle, replace it.
4) Do a quick vacuum leakdown by spraying Carb Cleaner around various vac connections and lines as the motor runs. If that changes the idle whatsoever, replace that line.

[BananaClip]

Originally posted by SoCal Driver
Don't think it's the timing belt. Could be a vacuum leak in the small tubing to the fuel regulator/damper or somewhere in the intake system.

Back to the timing belt; when is the last time it was replaced? These are good for about three years or 30,000 miles.

I had this exact problem back when I was fighting with the check valve that goes to the hoses on the damper and regulator.

[F18Rep]

Gee, I would have included the TPS...Bruce

[SoCal Driver]

TPS will give problems when you let off the throttle and the engine comes down to an idle.

I'm also thinking O2 sensor.