On the way to work and back home I had a few times where the car almost completely lost all power at almost exactly 3000 rpm under load. It seemed to be at about half to two thirds throttle. It doesn't seem to do it all of the time just intermittently. It felt as if the ignition was cutting out or it was being starved of fuel. When I floored the throttle it would clear right up and run fine. Later at home with the hood up and it running I didn't see any sort of light show or anything obviously amiss. It idles fine and when I rev it in the driveway under no load it doesn't stumble. So I'm not real sure what to make of it.

The car is an 81 US 5spd. Since I got it a year or so ago I've been slowly trying to bring her up to snuff. Its always had a bit of a flat spot in the mid range but its gotten better as Ive done things to it and driven it more. As far as the engine goes I've replaced the plugs, wires, cap, rotor, oil, fuel, and air filters. I've been planing on doing an intake/fuel system refresh (boots, vacuum lines, injector cleaning etc) but I'm not sure if that would or wouldn't have anything to do with it.

Thanks in advance for any thoughts tips or advice.

Eddie

 

Is it a CIS or FI engine? I recall when the change was made but the FI's AFM (air flow meter) can wear out and develop symptoms like this.

 

Its L Jetronic. If it was somthing like the AFM how do you test it? I assume their is a write up on the forum or in the wsm.

 

Remove the lower filter housing and the AFM unit is right bellow it. I can't remember for the top of my head what pin you need to check, maybe someone else can post this, but the method is to check the correct pin, with a ohm meter, while moving the "barn door" (flap panel in the AFM housing) and see if the reading is steadily rising or falling. If there is a flat spot, the multi meter will show it.

 

I had a guy come up to me in the Target parking lot and tell me he sees a black 928 in Cape from time to time. Probably yours as the only other one I have seen over there is white.
Sorry can't help with the L-Jet.

 

Yeah, its probably me. Its my daily driver, so it gets driven all the time. I don't know if I've seen the white one around at all though.

 

Clark's Garage (944 community) has an excellent write-up for testing and adjusting the pick-up arm on a Bosch AFM: http://www.clarks-garage.com/ Goto: Shop Manual/Air Flow Sensor Michael

 

Thanks guys for the ideas and links, I'm going to test it tomorrow after work. I'll report back with my findings.

That reminds me, the 944 I had did almost the same thing a couple of times on a long trip. I wonder if it was the same thing?

 

I tried to test the AFM according to the link that bigblock provided but the number of pins are different, so I wasn't sure which is what. Instead I just took the whole assembly out and cleaned it a bit, and adjusted the throttle cable a little and took it for a test run.

After about a half hour drive I didn't have any loss of power or hesitation like the past few days and it seemed to run a little smoother through the whole rev range. It wasn't night and day smoother but better none the less with no loss of power/hesitation. I'm going to cross my fingers and hope that that was it. Thanks for the help guys.

Eddie

 

Glad you got some improvement. I did not know about the difference in wiring. I have not done this on a 928. I was wondering if you were able to pull the cover off of the potentiometer. If there are grooves worn in the resistor track, you will get irregularities in throttle response (A/F) As highlighted in that DIY, you can re-aim the arm and give the resistor a new track.

 

See if you can find anyting here: http://www.nichols.nu/tips.htm