No Throttle Response on Cold Start/'87 560SEL

[jcantor]

I've been lurking for a couple of weeks while trying to deal with some poor performance and very poor fuel economy on my '87 560SEL. Reading through a variety of threads has been very informative and given me some ideas as to what may be causing my problem.

However, just last week, the car developed another new symptom: immediately after a cold start, there is absolutely no throttle response. The car starts fine (always has) but now will remain at idle speed for about 10-15 seconds no matter what position the throttle is in. This can have the very disconcerting affect of lurching one forward when it does finally decide to respond. Hot starts are not a problem.

Here's what has been done to the car preceeding this new development as I've been trying to correct the original problems:
* new plugs and wires
* new cap and rotor
* new air filter

Since the dead throttle problem started, I've corrected a very plugged catalytic converter which seems to have improved the original performance and fuel economy somewhat and am about to deal with the O2 sensor which has also been implicated.

Any ideas on what could be causing this strange throttle response? I would not be so surprised if this were a much newer, drive-by-wire car but with an older car and a mechanical throttle linkage as far as I can see, I'm puzzled.

Jeff Cantor
Ewing, NJ

MBZ:
'87 560 SEL
Others:
'67 Dodge Monaco (my toy)
'88 Buick LeSaber (wife's)
Previous:
'96 Chrysler LHS (totaled)
'87 Chrysler 5th Ave (sold after 240K trouble free miles)
'73 Plymouth Satelite (sold after 175K ok miles, lots of rust)