95 E300D won't accelerate around 50mph and loses power - PeachParts Mercedes-Benz Forum

djmono · #1 11-15-2012, 01:30 AM

The following is regarding a 95 e300d with 212,000 miles.

I'm having a hard time figuring out why my car is doing bizarre things on the highway. Here's a detailed list of things that may help narrow the solution for the experts on here:

1. I had several bad glow plugs and decided to replace them myself. I removed the crossover and manifold and got 4 of the 6 out/changed.

2. When I removed the manifold, I heard a clanging in it and noticed that a resonance flap was broken from the bottom of the manifold. This has since been replaced.

I drove it around the block and all seemed normal.

When I took the car on the highway it began to act VERY strange. It would no longer accelerate past 55mph, give or take 10mph. It is especially noticeable while going up an incline on the highway. It is losing power if I keep constant throttle and will hover around 50-55.

If I slam on the pedal at this speed (engaging the kickdown), it will downshift and rev to 4k rpms (nothing more) but will not accelerate. When I let off a little it will shift hard and go back to ~2200 rpms, yet I still won't have power. It feels like it is trying to change gears (a little surge, but nothing crazy), but there is nothing noticeable on the tach/revs that would lead me to believe it was slipping gears.

I then drove it up a hill at 35mph and it started to lose power. It seems to only happen under load.

Here are some other things to note:
-The EGR is not deleted and is functioning. I tied the flap open for 2 years and it drove fine. I untied it to try to narrow down the culprit.
-My mechanic replaced the other plugs
-The transmission fluid is at the proper level (checked while warm and running)
-The intake manifold has been fully cleaned, the GP inlets reamed and all crankcase breather plastic parts/tubes fully replaced
-There are no fuel/oil/tranny fluid leaks.

This car has been running like a dream other than the rough cold starts symptomatic of faulty glow plugs. The lack of power began after the glow plugs were replaced and the manifold, etc. were put back on.

What could possibly be causing the lack of power only at highway speeds or going uphill?

I hope this makes sense and someone has an idea of what the issue may be.

Many thanks, as always, to the bright people on this board. It has been a valuable resource for me for many years.

vstech · #2 11-15-2012, 05:25 AM

fuel filter?
air filter?
not sure if you can see the IP on the car, but if you could have someone floor the pedal (engine off!) and you watch the travel see if it reaches the stop? that much engine work, something could be out of place.

benedict · #3 11-15-2012, 06:07 AM

X2 on the fuel filter and air filter and tank strainer also a possibility.

A bit of a coincidence that it happened right after the jobs you completed.

It might pay to lift the crossover pipe off again and check with a torch that nothing has been bumped off the IP or any other vacuum lines bumped off - very easy to do.

vstech · #4 11-15-2012, 06:10 AM

note that above poster is in Australia! "torch" is not a flame producing device!!! it's a flashlight!

benedict · #5 11-15-2012, 06:47 AM

Quote:

Originally Posted by vstech

note that above poster is in Australia! "torch" is not a flame producing device!!! it's a flashlight!

Oops! I usually convert it back to US being a US forum but I didn't spot that one!

djmono · #6 11-15-2012, 07:55 AM

It's definitely oddly coincidental that this is happening after taking the manifold, et. al. off the car.

Another thing, when I was taking the throttle linkage off the top of the valve cover, I stupidly unscrewed the linkage to remove it. After I did that I noticed that all I had to do was squeeze a ratchet under it to get to the bolt holding it in place.

Is that Bowden cable that goes to the transmission? What's the proper procedure for reinstalling? I hooked up the linkage and tightened until there is no play...

I will look at those filters.

Thanks for the torch explanation

!

scottmcphee · #7 11-15-2012, 07:59 AM

Rescue the rag that you left in the intake manifold when you were cleaning it?

djmono · #8 11-15-2012, 08:33 AM

Wouldn't that be funny! I'm pretty certain that is not the case, but will look nonetheless.

NY300SD · #9 11-15-2012, 08:44 AM

Watch the fuel lines for bubbles.
Replace fuel filter.
Fix bowden cable. I don't think screwing it in all the way is the answer, needs to be adjusted.

vstech · #10 11-15-2012, 09:00 AM

Quote:

Originally Posted by djmono

It's definitely oddly coincidental that this is happening after taking the manifold, et. al. off the car.

Another thing, when I was taking the throttle linkage off the top of the valve cover, I stupidly unscrewed the linkage to remove it. After I did that I noticed that all I had to do was squeeze a ratchet under it to get to the bolt holding it in place.

Is that Bowden cable that goes to the transmission? What's the proper procedure for reinstalling? I hooked up the linkage and tightened until there is no play...

I will look at those filters.

Thanks for the torch explanation

!

that is certainly a problem. set this way, the transmission thinks you are holding the pedal to the floor... it may have even damaged the cable/bowden connection inside the transmission...

chazola · #11 11-15-2012, 09:18 AM

If your car was working ok before the GP work it's unlikely to be fuel/air filters etc.

Best bet is to work backwards and take the crossover pipe off again, and look for anything obvious. As you know there's a lot vacuum and electrical connections under there and one or two could have been left off or plugged in incorrectly. The flap next to the EGR is tied open/opening fully with full throttle right?

Also check the bowden cable is not trapped as it routes under the intake etc.

To adjust the bowden/pressure cable on these, it should be disconnected at the ball socket on the valve cover, then pull the cable 'till it starts to feel in tension. The socket should line up with the ball... if not, screw the plastic adjuster nut in or out. I've found the amount of thread showing on the plastic nut/screw is usually around 10mm +/- a couple of mm when adjusted properly.

djmono · #12 11-15-2012, 10:11 AM

vstech-
I don't think I worded that properly. I mean I tightened it until it has no play prior to pulling on the throttle. I will reset it per chazola's comment, but I believe that is how I set it initially.

Will report back soon.

Thanks everyone!

djmono · #13 11-15-2012, 11:41 AM

It looks like the Bowden cable is attached correctly.

I drove it around and when I hit around 50-55, it starts to lose power. It will slowly climb to 60-65 if I'm on flat ground, but it feels like there isn't fuel getting to the engine. At this point, the car does a slight surge, but nothing that lunges or anything. It feels like there's a governor.

I don't see any vacuum lines that are not attached.

I called my mechanic and he said to try replacing the fuel filter. That's on order and will be here on Saturday. I just can't believe it would coincidentally be that considering it was working perfect before I removed everything to do the plugs.

Jim H · #14 11-15-2012, 12:08 PM

I don't believe that a fuel filter would 'choose' this specific time to plug up...

I would go back and look really, really hard at the resonance flaps that you replaced, including all linkages and vacuum lines. Perhaps the flaps are binding and can't move? Perhaps they are not getting a signal to move?

Good luck!

djmono · #15 11-15-2012, 12:12 PM

If the resonance flaps on the manifold aren't moving, would it cause these symptoms? If so, what if I open them and remove the vacuum to the flaps? Would it still run like this?