1989 420 SEL Engine idle frustration

[cazdav]

My 89 420 sel is a great car but we have been unable to accurately solve the problem of the irregular idle. I have been to an independent mechanic and a dealer here in San diego. (Suprisingly the dealer was absolutely useless, 150 dollars later they made it worse!! I don't recommend the local major dealer here Carlsbad)

Ever since we got the car it had an intermittent and irregular idle that progressively worsened over several months. In an effort to rectify the issue. I have had the plug wires, spark plugs, all fuel injectors, both fuel pumps and some lines replaced.

the car in Park idles at around 600 rpm and at that time the oil pressure gauge and the rpm gauge will rapidly fluctuate together in synchronicity. In Drive while holding the brake it will idle at about 450-500 rpm and also cause the oil psi and tach to fluctuate in the same manner. I have power braked and raised the rpm to about 650 and the idle improves however not completely and just seems to mask the real issue. It's almost like it's missfiring but nobody can diagnose why. I thought about a new cap and rotor but the current ones are 7 years old.

In reverse without holding the brake or applying any gas the car will not backup smoothly it will just "chug" along as if you kept applying the brakes off and on. the car accelerates beautifully.

Anyone out there own one of these 420 sel's and have had any similar problems?? thanks for your help in advance

Regards

Dave:flash:

[hotchkissscott]

i have the same problems with a 420sel -1986. no one will help me did you ever get yours fixed ???

[papatho]

I have a 420 sel 1987, lately my outside temperature gauge is reading 90-103 F and while it is winter right now, any comments on hoe to fix it?