Another 300E rough idle cure

[psfred]

My 300TE has been plagued by a rather rough idle since I got it about four years ago. I've done all the "normal" fixes (new idle control valve hoses, etc) and set the mixture, but it was never really right.

It had a serious throttle lag problem, along with a stalling on hard stops problem, fixed by repairing the vac leaks and cleaning the idle valve.

Last week my mother complained that it was stalling again, and sure enough, it did, but only on stopping, or so I thought. Cleaned the idle valve again, checked for leaks, checked the mixture, etc. Worked fine for me, then stalled again for Mom the next day, but this time while driving off idle.

Pop, on goes the light bulb and I scurried off and bought a new fuel pump relay.

Wonder of wonders, the rough idle and most of the low speed vibration is gone, and the gas milage seems to have jumped up, too!

Who'd a thunk that a bad fuel pump relay would cause rough idle? I suppose the real problem was continuous on/off cycles on at least on of the fuel pumps, cuasing oscillating fuel pressure, which in turn caused the EHA to float around all over the place.

Sure does run nice now! All I have to do now is get the new evaporator in next week -- Mom is having a cataract removed on Wed, so I figure since I'm gonna take two days off, I could start the removal process Tuesday, get any parts I still need on Wed for Thurday delivery, and button it up on Thursday evening.

Always something....

Peter