400E engine question
 

:confused: hi -

i have a 1992 400E with just under 106K miles. in park the engine revs fine until it gets to about 4500 rpm, then it starts missing in a big way. it shakes the entire car. i was having the a similar problem when the car was on the road (it's off for the winter), although at a lower rpm. it just felt like a little hesitation every once in a while - not a big deal but noticeable nonetheless. the plugs look good and we replaced the rotors and the caps, but not the ignition wires.

any feedback is appreciated

How about don't drive it above 4400 RPMs. I don't think I've ever had mine over 3,000.

Two things come to mind - ignition problem, fuel problem. I know, it doesn't leave much else :)

I had a problem with one of the coil wires of the S420 resting on a bolt head. You could see where arcing had taken its toll on the insulation. The car would buck in higher rpms under load.

Could also be a restriction in the fuel system like a clogged filter.

Some recent MBs have a rev limiter when not in gear. I don't think the engine goes into convulsions. It just won't rev beyond a certain point in P or N.

Sixto
95 S420
87 300SDL

thanks for the feedback....
i normally do not make it a habit to rev the engine, but there will be times (like when the engine downshifts during a passing maneuver) when the engine will need to rev, perhaps past 4500 rpms......

if it were a fuel supply problem, wouldn't it occur throughout the entire rpm range? when it was at the shop, the ignition wires were supposedly checked to see if anyone of them was bad - they were all good.

i will call the local benz dealer to see if they can tell me whether or not the car is equipped with a rev limiter.

thanks for your help

A fuel line can be restricted yet allow some flow. If your fuel system can flow only half of what it should, you'll have no trouble cruising which probably takes all of 25 hp. Step on the pedal to merge between semis and there isn't enough flow to support 250 hp.

Has the wiring harness been replaced? Do you get random check engine lights?

Sixto
95 S420
87 300SDL

sixto -

i guess i will have to have the fuel line checked. i do not get any warning lights on the dash. to the best of my knowledge, the wiring harness is original. is there any chance i have a bad ignition coil pack?

thanks for the feeback

There's a good change you have a bad coil... or both. They're not coil packs in the distributorless sense of the term.

Sixto
95 S420
87 300SDL

I can agree that this really sounds like a fuel filter problem!
They are so cheap and easy to replace anyways...

And at 100,000 miles... I would change it!

If you still have problems after R&R'ing the ignition system I would suggest the wiring harness. Do a search on M119 wiring harness and you will find that due to manufacturing these harnesses with some sort of biodegradable insulation, the harness (wiring insulation) does not last well at all. Very common problem for M119.

New harness is $400 - 500 IIRC, and it is a reasonable DIY from my research. More about this also at 500ecstasy.com.

Rgds,
Chris W.

thanks to all who have responded

what other symptoms might i expect if the wiring harness were bad?

thanks in advance for your help.

Maybe I missed this in the posts but when was the fuel filter changed?
 

Maybe I missed this in the posts but when was the fuel filter changed?

The fuel filter starts restricting the fuel flow from the very first turn of the key and slowly declines, reducing fuel flow more each day until you have to change it.

Symptom of filter plugged is fuel starvation, much like running out of fuel, especially when under heavier demand, Acceleration! You just don't have the fuel to meet the demand.

With higher and higher fuel costs we all start to look at lower cost stations. This can be a leader to more contaminated fuels, all fuel has the possibility of crud in it or there wouldn't be a filter. hence, possible premature filter failure? Even quality gas suppliers scrape lower into the ol' barrel when prices are higher! Than means quality decline!

trants4md :sun_smile
______________
85 500SEL
80 Leland TR7 Convertible
And Some American Stuff
94 Dodge Ram
93 Chev Lumina APV
79-81-83 Forzda

I pretty much have the same problem....engine cuts out momentarily at high RPM's while accellerating rather rapidly. (like you might getting onto a 2 lane highway when they are all going around 60-65 mph) I have had the wiring harness replaced and the fuel filter also. I also have a new ignition module (not cheap) new coils (one was busted), and recently, new caps and rotors.
Yet still I have this phenomenon. I suppose about he only thing left to throw at it (besides the kitchen sink) is new plug wires (cheaper than the module, but still nothing to sneeze at)
Then again, I could get some holy water and throw it on the engine...if it catches fire, I'll know for sure what the problem was...

finally! - somebody with a similar problem. i was beginning to think mine was the only vehicle doing this...
i have not replaced the fuel filter yet, but i will do so because it is probably still the original unit, and i do tend to let the car get low on fuel, so there very well may be some sediment blocking the fuel flow. i will start here and see what happens - i suppose i should check the ignition wires again to see if anything was missed at the shop - if they are good, i'll go onto the next thing and just start eliminating the probable causes. i'll hopefully catch it sooner than later, if at all. i've had no other electrical glitches to indicate that it might be the wiring harness - no warning lights and everything works as it should. i am aware that this is a common issue with these cars, but i also have to practical in terms of what i am willing to spend on the car and probably will not replace it unless it absolutely needs it.
thanks for all the feedback - i will keep you posted as to what happens

the car is equipped with a rev limiter that works when the car is in park or neutral.
however,i have experienced the same symptoms as larry delor when the car was last on the road in the early fall. there was hesitation in acceleration when the engine was under load. i hope to have the car back on the road for summer - i still plan to change out the fuel filter and check the ignition wires, too.
thanks to all those who responded - i will let you know how things go when she's back on the road.

Switch brands of gasoline. I didn't use the usual stuff last few tanks and I was getting the symptoms you describe and I switched back. Try it.