c200 hesitation
 

Hey guys,

After suffering from some problems with my 95 c200 ive replaced 2000 dollars of parts to no avail.

When the car is cold, it smells really rich, black plugs as in rich mixture and when pulling away it will hesitate. It will drop revs go like its going to cut out, then if you take your foot off the accelerator it will pick up. Putting your foot down further seems to flood it and stall. This is a result of a wiring harness going bad.

Have replaced

wiring harness
idle speed actuator (throttle body)
engine temp sensor
air temp sensor


Still got the problem! Also when reading from pin four of the diag plug I get four pulses, i think this is to do with MAF over upper limit???

Have also swapped out the MAF, makes no difference. Have also tried another OVP! Nothing!

HELP!

Check the fuel pressure regulator.
Do a fuel pressure test.

..
 

Where abouts is the fuel regulator on these? Im only familiar with the setup used on the old 190e's. Does anyone have the specs for pressure etc?

I don't have any specs on that engine . Only US ..
.. but if it has a fuel rail , [ EFI] it would be up front with a vac hose connected to it.. if so, pull the hose and see if there is any fuel evident. Should not be any.. if there is, it has a ruptures diaphragm and is allowing pressure over spec., which will cause the rich running and limit codes.
Is that a RHD car???

.
 

yea its a rhd ex japan model

Is it EFI 4 cyl. with coils over two plugs?

yep
 

Its EFI - HFM sequential fuel injection.

The coils are under the intake manifold however.

then it has a fuel pressure regulator..

Do a quick check for any vac leaks as well..although I suspect high fuel pressure.

Is that a 38 pin diagnostic connector??

round
 

yes its the 38 pin round one.

A comparable system US version would have FP of 3.2-3.6 bar at idle,closed throttle with vac attached...3.7-4.2 with vac line disconnected.
that will get you started.
I have no idea what Japan uses for engine management mandates for specs or codes/emmisions..

fine
 

Fuel pressure is fiine. Compared it with another c200 of the same year that has no issues.

Tried a new set of plugs too.

Something that might be related. The throttle acutuator hums with the ignition on (engine off) continually - but in a e230 it only hum sfor a few seconds... Related?

o yea
 

Not to forget the surging idle. it only surges when in gear.

update
 

Heres an update.

Got the dealer to check the fuel pressure for me - its ok.
Dealer re - read the codes and got lambda above upper limit and mass air above upper limmit.

Have got o2 sensor on order, however i swapped a mass air metter out of another car which is fine, and the error kept reccurring. Why?

Also I tested the 02 sensor and i get 0 volts cold. and it lazes around .6 .5 volts..... no fluctuation on rev increase - guessing its stuffed?

cheers

josh

....
 

O2 sensor replaced.....now back to the dealer. Know were getting a voltage drop at the ECU - Replaced OVP no change any ideas?