90 300SE Start / idle problems
 

Hi,
The car is a 1990 300SE with 189,000 miles

This past winter the car would not start in the
morning when it was about 15 degrees F or lower out.
Car would turn over but would not start. On 3
occasions I had to add 2-3 bottles of dry gas each
time for it to start. Also recently the engine seems
to start rough in normal weather and idles roughly.
Once the car is going about 10mph it is as smooth as
glass without any hesitation, surging or misfires.
Engine does not smoke at all. Changed out fuel filter
and that did not help. Platinum plugs, wires rotor
and cap were replaced about 60,000 miles ago. New air
filter, EGR valve and O(2) sensor on 11/02,

When my car was in for an alignment at my local MB
dealer, I had them check out the car’s problem. An
initial diagnosis was performed but the technician ran
out of time. Below is what was written on the service
receipt.

“Performed lambda test, found intermittent
reading-possible control module for cold start
problem, may need fuel distributor and injectors,
possible coil”

what and where is the control module? Is it the engine
computer?
What are the symptoms for replacing a fuel
distributor? That is one expensive part!

When should injectors and a coil be replaced?

I figured the coil is fine because there is no problems
at above idle speeds.

Any help is appreciated, I really do not want to put
much more money into this car.

My 2 cents.

Fuel dist., injectors and possible coil....all 3 ???? Sounds to me like they're guessing - throwing parts at it.

There is a cold start valve on this vehicle. Could be an issue in the cold weather you describe. Check archives here.

You mentioned plat plugs. If you still have 'um, get rid of them and use Bosch spark plug H9DC0. There's also an H9DC, but it's electrode is not as wide as the H9DC0. These cars idle better on the plain copper plug.

MB says to gap at .032(that's what it converts to). Some say to go as high as .040. I set mine in the middle of this -> .036.

1991300SEL
thanks for your input. i will change out the plugs this weekend and do a search on the cold start valve. It doesn't idle smooth at all even though the tach does not move at all.
Dan

Could it be the OVP relay causing the problem?

It's been reported here many times that the plat plugs cause bad idle problems in the 103 motors. Mine came with the H9DC0's and have never had anything else.

I would start with the spark plugs since the one's you've got are not right for your car.

I've never had an OVP issue but seem to recall reading here that an ABS light is oftens times indication of a problem with this part.

The OVP gets blamed for everything conceivable.

Look at M.B.DOCs comments in this thread.

http://www.peachparts.com/shopforum/tech-help/45977-how-do-you-test-ovp-check-if-its-working.html?highlight=ABS