very Poor Acceleration 88 300E M103
 

Only when cold until engine temp is above 80 acceleration is non existent.
I have replaced many parts.Cap,Rotor,all new Bosch Injectors,fuel pump relay,air filter,cleaned IAC valve tested Iac under different voltages,tested o2 sensor (only 1 yr old) voltage fluctuates showing o2 sensor doing its job.
tested fuel pressures at upper and lower chambers of fuel distributor.both ok.
vacuum is good.Idle is ok for a M103,acceleration is great after warm up.I have also adjusted mixture at the x11 port.no help. adjusted bowden cable and throttle cable. no help!!!!!!! Need help! :confused:

How old/many miles on the cat?

Cats fine.

I suspect the EHA. Give it a 1/4 turn richer no more and see if it helps.

Test the air flow meter potentiometer if you have one (electrical gizmo similar to a throttle position sensor on non-Mercedes vehicles). That gizmo ONLY has to do with acceleration and telling the computer/EHA to provide more gas.

'88 M103s don't have an external electronic air flow meter, but I believe one was added in later years.

I'm assuming that there is no check engine light, but if there is, read out the codes.

Poor engine power below 80C engine temperature indicates a problem somewhere in the mechanical half of the CIS-E system. It actually goes into closed loop mode at about 60C, but I suggest you remove the OVP, which will disable the E part of the system and determine whether it still runs poorly at normal operating temperature. If so then the E part of the system is probably okay.

Do this when the engine is warm as all cold start enhancements are in the E part of the system, so it will be reluctant to cold start without the OVP. Also expect a check engine and ABS light when the OVP is removed.

Duke

I was referring to a Bosch mechanical fuel distributor which has a mechanical air flow meter. Tis a round disk inside the air cleaner which goes up/down as less/more air is drawn into the engine.

That mechanical air flow meter on some cars has an electric "air flow meter potentiometer" which gives an input to the CIS-E engine computer - adds more gas upon acceleration.

Here is a bit on that...
SG-Motorsports Air Flow Meter Potentiometer Replacement

Original cat and it has 148,000mi on it.

If it was the potentiometer would it not malfunction at all temps? Keep in mind as soon as the engine temp hits about 85c it is like a new car with no problems and great acceleration! this is why I am so puzzled :confused:

Excellent article I can test my current potentiometer and see if its bad or out of adjustment:cool:

Somewhat true...but it also influences/controls idle rpm. If its off, it will either not start, or idle at 700-1500rpm.

The cat would be one of the last items I would check. If you had issues under any condition, then it could be suspect, but its fine otherwise. Most people will toss the cat FAR before its useful life. I prematurely replaced my 300TE's cat which was fine. My old 260E was burning 1qt a WEEK for over a year and it blew through emissions right before I parted ways with her. The Genuine MB cats from this era are incredibly good.

I still think you need to look at the EHA and give it a 1/4 turn rich. If it doesn't do anything, 1/4 back and nothing has changed. All of 10mins to do it.

Fuel distributor pressure is close to worthless. Its USUALLY either in spec or not. If its in spec, it still doesn't mean the distributor or EHA is OK. It just verifies there are no restrictions in the "majority" of the fuel chambers, and it says nothing about EHA performance.

In the next month I will have to smog my 300TE which has historically struggled with emissions. I finally replaced my EHA with a new unit and it completely changed the acceleration performance, idle and fuel consumption even though pressure's were to the T. I have changed nothing else since last emissions. Once I take it I will post the results which should give a pretty definitive result of how the EHA affects emissions (namely NOx for me which is what I always failed, or borderline passed with some ISOHeet help). With the increase in acceleration and 1.5mpg increase in fuel economy, I am confident the issue is gone and I will pass no issues.

cold start valve ?
 

Could it be the cold start valve? does it just shoot extra fuel during start or will it provide some extra fuel during the entire warm up process,also is it controlled by the coolant temp sensor? how do you test the coolant temp sensor,does it ohm out differently at different temps maybe there is a chart. It is the green one with 2 prongs.I had replaced the sensor 3 yrs ago for another problem I was just throwing parts at. Maybe the new one went bad.
I will also try the EHA adjustment. There is a boat load of 124 cars at the local pick a part I will grab a couple of EHA's temp sensors,and cold start valves for $5 bucks you cant go wrong ,these are very pricey items:cool:

ps2cho, which way is rich on the EHA after I take the cap off?

I have a question, does fuel actually flow through the EHA? Could it plug from sludge and rusty gas?

EHA adjustment
 

Problem solved! adjusted EHA clockwise to make it richer. It idles better and accelerates cold great.Thanx for the advice ps2cho. When I took the EHA off and removed the cap I inserted the 2mm allen wrench into the adjustment screw and it felt very loose so I thought it was the wrong size but it was turning all along it is a very loose adjustment screw! So I can not say exactly how much I turned it in the enrichment direction but I was really lucky because the car has never run so good!:D

Im sure you meant a 3mm allen wrench.