low power on acceleration - Page 2 - PeachParts Mercedes-Benz Forum

haasman · #16 12-09-2002, 02:37 AM

psteinke

A MBZ dealer tech told me to bleed the injection lines at the fuel distributor (be careful of raw fuel spilling over a hot engine!) and a lot of crap came out. I actually did this twice. It seemed to help quite a bit.

You said you "checked the fuel filter and fuel pressure" .... a clogged filter will definately slow you down.

On a long shot- you could pull the fuel tank sending unit and take a look into the the fuel tank.

Whats the history on the car?

Haasman

jjrodger · #17 12-09-2002, 05:00 AM

I had a C200 that wouldn't kick down or accelerate hard. Turned out the throttle cable was loose and so I wasn't opening the throttle fully, even with the pedal pressed right down.

#18 12-09-2002, 10:18 AM

I checked fuel pressure by putting a gague on one of the output of the fuel distributor and fourn 78psi there. This is really not a good test, though because there is no flow there. All that this tells me is that the fuel pump is good and the fuel pressure regurlator is not letting all the pressure go right back into the tank. THese are valuable things to know, but it does not mean that there is enough pressure when the injectors are allowing fuel to flow through them.

This is a great idea to bleed the outputs of the fuel distributor. Also, I suppose I could have the injectors cleaned professionally. Do they use back pressure?

Paul

Pilotx1 · #19 12-09-2002, 02:24 PM

getting new injectors might be both simpler and cheaper than having them cleaned, the materisl that the injectore are mde from does actually eropde after years of usage from the gasonile flowing thru them, nothing can be done to avoid this. a great place ive found to buy autoparts for our mercedes cars is www.expressautoparts.com they are cheap, deliver fast and if you spend over $50 in parts(not hard on a mercedes) you get free shipping.

#20 12-12-2002, 11:31 PM

I put a new injector in cylinder #4. #1 and #4 had a black spark plugs, and #4's spray pattern looked poor compared to #3, so I replaced #4, but this did not help at all. I still get low power on acceleration and top speed of 64mph.

blackmercedes · #21 12-13-2002, 03:33 AM

Have you tried a compression and leakdown test? I'd start there, and then if it's okay, isolate fuel and spark components.

Your black plugs are not a good sign...

...are they oil fouled?

keithed · #22 12-13-2002, 11:57 AM

Try a flow test before and behind the converter, to see that its not stopping up.

You'll have to bring it to an experienced exhaust shop for this. Its fairly cheap to rule out exhaust issue as power problem.

K

#23 12-13-2002, 12:02 PM

The plugs are not oil fouled. They are fuel fouled. Also, compression is 125psi on all four clyinders. I think spec is 130 - 150 for this car, so I am a little low, but absolute min is 109, so I am in there.

I tried manually setting the eha current with a potentiometer while I drove, but this didn't give me extra power either. STill top speed 60mph.

Paul

Pilotx1 · #24 12-13-2002, 04:18 PM

when you get to 60 what does the car do? is it like the engine hits a "wall" and just wont rev any higher? is the engine revving really high and has reached its rpm limit?

#25 12-13-2002, 07:30 PM

My car has low power at all speeds (rpms). In first gear when wind resistance is not big yet, the engine will go up to over 4000 rpm, but in top gear, it wont rev that high, because I am up to 60mph and the wind limits the speed.

Pretty sure the car is in mechanical mode and computer control is not working.

Though I manually adjusted the eha current while driving. between 0-6mA, there was not difference, and then between 6-12mA the performance got worse and worse. I never got better proformance, only worse by doing this.

Paul

Pilotx1 · #26 12-13-2002, 07:51 PM

Have you tried blanking the computer?, on my car it is located on the firewall about 6 inches inboard of the battery. disconnect the ground cable on the battery and carefully remove the ECU from the harness. leave the ECU disconnected for about an hour, this will allow the capacitors in the ECU to completely discharge and thereby erase any memory that may be stored onboard the ECU it wont however erase the hard-coded engine profile and operating data that the computer uses for engine managment. as a result of losing the volatile memory that the computer stored from data received from various engine sensors you may have poor drivability until the computer can rebuild its custom engine operating profile.

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