200 10V stumbles, poor mileage

[David Michael]

Konstantine,

On and off I have had several bouts of fixing my poorly running 200 10V.
Some of the issues it sounds like you are familiar with, but here are some
things I learned:

1. Air leaks. Double, then triple check. Use Scott M's site as a guide for
where to look.  Injector seals, valve cover gasket, rubber "igloo" and
intake hose clamps all good places to look. All are easy except for the
injector seals..

2. I fought a poor drive ability problem for very long time before I found
that the Hall Sensor in the distributor was sending false signals. I finally
found that when I hooked an O-scope up between the distributor and coil, and
found there were random "ghost signals" inter-spaced with the sine wave. New
dizzy fixed a world of problems.

3. When you set your idle mixture duty cycle, make sure you also set the
idle valve control current with the bypass air screw. It's best if you have
two meters - one for the mixture duty cycle and one for the bypass valve
current. If you cannot set the idle air valve it to 430MA, look for the
reason why......

How steady is the duty cycle at idle? It should not swing by more than about
30%

4. I had a very strange problem where my control pressure regulator was not
constant - it would randomly change the control pressure by ~5psi. But that
affected the part throttle accelerating, not idle. New WUR fixed that.

5. Make sure your air meter flapper plate moves without binding - there is a
roller bearing under the fuel distributor plunger, and mine was occasionally
sticking.  I fixed it by spraying some  lubricant through the idle mixture
setting hole. You have to bend the tip of the lubricant can little red hose
at 90 degrees to do this. It would be better to remove the fuel distributor
from the AFM but that is a PIA.

6. You need to find out if your car is hard to start because there is too
much fuel or too little. I did have  a drippy injector once, and it would
cause hard starting after 15 minutes - but you could also smell gas. It also
had no affect on idle.

7. Other things I have done that may or may not have helped: New coil, new
plugs, new TDC sensor, new air cleaner

Good luck

Dave
90 200 qa 240k