Hello,

I have a 740 Turbo wagon (89) with a tachometer that twitches. When you start the car up it will idle normally for a minute or two followed by the twitching tach. You can't feel or hear the engine changing pitch in response to the fluctuating tach except when the fluctuation jumps above 2000 rpms. Most of the time the fluctuation is from about 800 to 1500 rpms or so, but may only be a fluctuation of between say 800 and 900 or 800 to 1000. When an extreme fluctuation occurs the engine often dies in response. Now what I've done so far is just take apart and clean the Idle Air Control valve which at least changed my idle from 1000 rpms down to 800 rpms. Before I got the car, the previous owner replaced power stage, distributor cap, rotor, plugs and wires, fuel pressure regulator, turbo, intercooler hose coming out of turbo, coolant temperature sensor, and AMM (although I believe this was may have been a used unit). Any ideas of what to test or replace next? Help me solve this so I can drive my car. Oh yeah, when you do drive it, it will almost always die while sitting and idling, although while in motion when the idle stumbles (tach jumps), you can usually give it gas to keep it from dieing.

Thanks,
Matt Campbell