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On 1/17/03 I sent this out to the list: Here's my situation: 1968 Squareback w/FI all stock Start fine Idles @ 1100-1200 when cold Runs fine Idles @ about 800 when warm for a while Then drops to 600 jumps to 1000 and drops to 800 again But still runs fine and smoothly At night I do notice the headlights dim and brighten with the idle fluctuation Points/plugs/trigger points/timing/value adjustment all OK Check fuel pressure some time ago but was at 28-30 lbs Any ideas?? Throttle switch, recheck fuel pressure? Russ Wolfe, Jim Adney and Phil Cain all responded with helpful suggestions to check the throttle switch, Aux air valve, hoses and tack which I checked. I still have my problem. I looked at everything again Saturday and found something which I do not fully understand. When I disconnected the hose from the pressure sensor the idle quickly increased which I expected. When I covered the end of the hose with my thumb the idle dropped and stayed at about 850 as long as I held the end of the hose. I tried a spare sensor and the same thing happened. I am going to replace the hose in hopes of a quick, cheap fix but I doubt this will help. I understand the pressure sensor measures the vacuum and enriches the fuel mixture at part-throttle and at full-throttle. It seems like either the throttle switch or the sensor may have a bad wire/ground as it cannot maintain a constant idle. What happens if a wire to either the switch or sensor is open? Is there a default mode or would the engine just quit running? Can the pressure sensor be adjusted? This link would suggest that it is but I haven't tried it: http://members.rennlist.com/pbanders/manifold_pressure_sensor.htm I am going to test the continuity in the wires from the ECU to the sensor and the throttle switch. I also have a spare ECU I can try if the wiring seems to be OK. Should I look at any thing else? Thanks in advance, Norman ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/