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Premium Member
W-1-2-3 Go!
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16,161 Posts
Discussion Starter #1
Hi folks,

Trying to get your collective wisdom to troubleshoot the odd acceleration issue my '89 190 2.6L has.

When the car is stopped, acceleration is weak. I stab the pedal halfway and it just jumps screaming but the pull isn't there. It's noisy but doesn't have much pull.

On the highway, it accelerates well. But it feels "too smooth" - I see the speedo move up but it has no "pull"...

The puzzling thing is that it USED to have this pulling force when flooring it.

This happened after replacing:

1. serpentine belt
2. serpentine belt tensioner
3. belt tensioner shock/damper
4. tensioner adjustment bracket
5. water pump
6. fan clutch bearing/bracket

In the same job I also replaced:

1. high tension wire from distributor to ignition coil
2. rear brake pads

I suspect the rear pads may be the culprit, but what are the chances that both sides could get stuck? How HOT or WARM should the rear wheels be after a 20-minute drive on the highway - are they supposed to be as warm as the front wheels?

The reason I suspect the rear pads, is one of my tests I saw the speedo drop as I just released the accelerator but my mind wasn't completely focused so it may have been in S (3rd) gear and that may have caused the heightened deceleration.

This has not happened before so I'm not sure how to go about inspecting the rear brakes. It's a pretty easy and simple job and I've done it many times before, but this is the first time it has happened to me (if it is indeed, the rear brakes).

When I moved the pistons back into the bore, I used the old pads as a buffer so I don't gouge the seals.
 

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1990 190E 2.0 Sportline
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17 Posts
I'll wager you suspect the rear brakes are dragging? if so are the rotors excessively hot after a trip?
 

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Premium Member
W-1-2-3 Go!
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16,161 Posts
Discussion Starter #3
Now I'm thinking it might be a few other things.

I've been reading on the transmission piston kits (K1, K2, B1) and I noticed this morning it doesn't just happen on 1st to 2nd, but maybe 2nd to 3rd also. So it could be a transmission or:

Do you think it could be restriction from airflow? It feels like the car is struggling to get power at 3 to 4k RPM. It sputters at that engine speed range (like when doing a U or a simple turn then you accelerate to speed). Above that, it's fine. However, it rocks the car a bit when it does this. The car feels like it's engine braking, THEN it surges forward once it overcomes this "obstacle"...

So since it's consistent at that RPM I would rule out the dragging rear brakes. I've read somewhere that they adjusted the duty cycle for this but if that's the case how does this have anything to do with the serpentine belt (and corresponding parts associated with the job) replacement? Does it now have more resistance due to a tighter belt?

I checked the transmission fluid - it's not red or pink, but dark colored. That's why I thought it could be a transmission issue. When I first got the car it banged into each gear (vacuum line was detached). However, the level is just right.

It's possible the problem has been there for a while, but never this intensity.

I'll be dropping by my mechanic tonight, and hoping for the best. I want to clean the throttle plate (not the MAS sensor plate, but that helps though it has already been cleaned before) and since the MAS + FD will be out when this happens, might as well clean the assemblies. Hopefully I don't see any cracks on the vacuum/rubber components! Some have been replaced before but not all.
 

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87 300D 5 speed
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5,320 Posts
Check that the throttle plate is opening fully when you move the throttle mechanism by hand in the engine. make sure your throttle cable is tight etc. The whole mechanism is overly complicated and prone to sticking. Otherwise it could be any number of things and it would be very hard to diagnose with out a thorough inspection.
 

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Premium Member
W-1-2-3 Go!
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16,161 Posts
Discussion Starter #6
Well, we tested to see if duty cycle was good. It was in spec and the needle fluctuated indicating O2 sensor worked. But it felt restrained so he thought it's a fuel delivery issue. Adjusted EHA a tad, reinstalled and readjusted duty cycle to compensate a little for the adjusted EHA. Felt better.

Made sure throttle linkage was in spec, bowden cable was okay, throttle cable was old and probably original.

Since I brought a new throttle cable we put that in. Felt much better (smoother) - I didn't know there was adjustment for the throttle cable in-cabin.

Now it responds better after a turn, at WOT (kickdown) and no more sputtering.

Glad it wasn't the transmission or anything major.

On my next oil change, we will have the transmission serviced with new filter.

This car is back on my "happy list" once more :D
 
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