My '89 300E was running great, all of a sudden it started blowing black smoke, low vacuum and the fuel range dropped in half.

I took it to a mechanic who swore it was ignition related and he replaced all the plugs, wires, and other ignition components. When I got it back, it ran exactly the same. When I returned it, he said it now needed a catalytic converter, Ox sensor, fuel pressure regulator, and fuel distributor. And he wanted about $4,000 to do the work.

I'm not convinced he knows what he is talking about, so I wanted to check here first. Does this sound right?

When I disconnect the wire on the EHA, it runs a lot better, less smoke and better mileage, but there is still some black smoke and I don't get anywhere near the mileage I used to get.

I appreciate any responses.
Phil

If you replace all that it probably will cure it... whatever it is but I doubt it's all necessary
1) When you say low vacuum... what does your economy gage do under what circumstances (at idle and under throtle)?
2) You can find out a lot with a multi meter with duty cycle setting at the X11 diagnostic port... (about$30.00) Do you have one? If so look at this link: http://www.landiss.com/mixture.htm

The oxygen sensor is a likley candidate for high fuel consumption. There is some about that at this thread: O2 sensor test and inverse duty cycle and others you can find by searching this site.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

I would start with some diagnostics.

Test the O2 sensor your self with a multi meter. You can unplug it under the drivers side carpet. Its a round connector. Connect your positve lead here and negative to ground. You should see a value between about .1 and .9 If you increase the rpm it should change. If no change it could be buggered.

After eliminating this then I would try adjusting the EHA. I had the same issues with a 190e. It was getting to much fuel ( your complaint). From memory I took the EHA off. Theres a screw on the back, remove this and you will see a little nylon allen screw. Turn this half a turn anti clock wise and see if it changes. Remember anti clockwise is less fuel clockwise is more. However fine adjustments are required. Have a play and you may get a setting which suits.

On another note if the EHA leaks it could be dead. There is no need to change a cat converter as it wont cause smoke and poor mileage. I think your dealer is a bit of a bush mechanic. I got taken for a ride when i took my c200 to the mechanic - always get a second opinion.

What I meant by low vacuum:
At idle, out of gear, economy gauge is at maximum.
At idle, in gear, economy guage is at the middle.
accelerating, economy guage is pinned at minimum.

When I disconnected the EHA, the economy guage showed better readings, but was still not running as good as before it started running bad.

I thought of the O2 sensor as the culprit, but I disconnected the wire to the EHA. I would think this would eliminate the O2 sensor from the equation, and the EHA would also then not add any fuel.

The EHA adjustment sounds promising, but why would it go out of adjustment so rapidly?

Thanks,
Phil

Sounds like a vac leak... Does it have power loss as well?
you can test for leak spots by spraying ether or propane around suspect areas and listen for an increased reving... might want to look at the breather hoses underneath for splits where they connect.
I wouldn't be suprised if you had more than one problem though...

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Yes, You mechanic is clueless!

He has already replaced a bunch of parts based on a false diagnosis.

Michael

__________________
Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E

Wouldn't a vac leak cause it to run lean?

Thanks,
Phil

Sorry. I think I got that backwards in my haste...
So maximum is all the way to the Left (best economy) and minimum is all the way to the right (worst economy).

Sounds like the needle should be a little further left in gear at idle than the middle of the gage though.

I wonder it that could indicate an exaust restriction.

Is there any power loss?

I still think your best bet is to get a DMM and check the mixture.

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html