Folks:

My '97 is still stuttering anywhere from about 1600 rpm to 2800 rpm when a light throttle is applied - accelerating thru this range up to highway speed is fine - car seems to have normal amount of power. Driving at 70 mph/3000 rpm is fine, plenty of power and smoothness. Just cruising though, and it stutters and misses until you step on the accelerator or let off.

I had the car in at an indy mechanic, who reported the flaps seemed to be working fine and hooked up his Startek system - no codes, which also rules out failure of the resonator flap components. Changed fuel filters, no improvement. He did finally swap out the battery because they noticed it was the wrong kind - afterwards he reported the stuttering went away. On the way to work this morning, the drive was much improved. However, later on the drive home it was back the same as ever. Car starts and runs smoothly every time, no weird electrical issues.

If not the flaps, what could it be? I've been searching for ideas - others have had this problem, the following were suggested:

Resonator flap transducers/crossover valve (if these failed, would throw a code)
K40
Vacuum line somewhere - how do I diagnose?
Clogged vent line
weak lift pump
Fuel injectors - why would the car run well above 3000 rpm though?
Something electrical - alternator alternatively is put under load/not under load, creating a stuttering effect on the whole engine. BTW, turned A/C compressor off to see if that was causing it, did not change anything.

Any other ideas? Do any of these ideas merit further investigation? I gotta get to the bottom of this.

Thanks,

__________________
Charlie

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'66 VW 1300 96K miles
'97 E300D 239K miles
'85 300D 203K miles (sold Sep 2012)