4500rpm, rpm, spudder, rev limiter... - Benzworld.org

300E · 11-12-2007, 06:46 PM

Hey guys... Sorry I haven't posted in awhile, but I need your help. Thanks to you guys this site has become my bible to all things Mercedes. I haven't updated my profile but I've owned a 300E, couple of 400Es, a 400SEL and now a 600SEL since my last post. Nearly all of these vehicles had to be put to rest because of an auto accident. I'm thankful for auto insurance but pissed at the person who did not see the parked 3000 lb vehicle.

This post is regarding the 600...

I've performed a search using all the the keywords in the title and have read through nearly every post until the post got off topic, but nearly all (if not all) did not provide the final resolution.

Problem: The 600 acts as if it has reached the rev limiter around 4500 RPMs during heavy acceleration (just enough for a downshift with or without activating the kickdown switch). If I ease off the gas pedal, I can continue to increase in speed. But, I have problems at 4500 RPMs without fail. This is extremely frustrating when trying to pass a vehicle or merge onto the interstate.

I've read causes such as low modulating pressure in the transmisson, rotors, caps, wiring, harness, MAS, etc. But no one who posed the question issued a follow up.

What was the fix that did the trick?

skipinschool · 11-12-2007, 10:00 PM

could be a few things... lets start with MAF (mass air flow sensor) check that out. get some quick dry MAF cleaner, you might even gain horsepower doing that

That was my best guess. Another issue with the W140's is the fuel filter. Get that changed. Its not expensive and it can work wonders. You might not be getting enough fuel in your engine quick enough to ignite past 4500.
Also, get some injector cleaner.... you could have some cloged injectors.
Change your spark plugs, could also be some misfires.
change your air filters. you might not be getting enough O2 into your engine
check fuel pressure regulators. could have low fuel pressure.
finally.... your car just might be in limp mode. idk how to explain limp mode, but those are some symptomes. do some research.

Good Luck. and please reply on this post w/ whatever the problem was because my cars shifting point is 4500rpms and no sputters.

NZ Benz · 11-13-2007, 12:33 AM

Hmm, I'd be suprised if it was spark-plugs because a missfire feels like you reach a certain rpm and then ease off the gas even if your not. That being said those are all good places to start for general good running of a car anyway and they won't hurt to be looked at and replaced if they need to. I'd do all those before playing with the gearbox because that is pretty much without fail costly.

Brett San Diego · 11-13-2007, 03:50 PM

It's not clear from your post. Will the engine rev past 4500 at all or no?

Brett

300E · 11-13-2007, 07:38 PM

You are correct. The car will not rev past 4500 RPMs. The MAF and air filters appear to be clean and in good condition. Fuel injection cleaner through the system renders no change in behavior.

miloking · 11-13-2007, 07:49 PM

is it posible that you fuel pump can be on its way out....or even just pressure regulator, what you describing is like car with turbo that has been overboosted and is not getting enough fuel near limiter...(as injectors and fuel pump cannot handle the demand)
There are ways to check fuel pressure but you will probably need shop to do it...

300E · 11-14-2007, 07:11 PM

It appears that the engine was not getting the oxygen it needed at the higher RPMs. I looked at the air filters (which were clean) but also removed a clump of what I can only describe as insulation (fiberous like insulation but black in color) from the right air filter housing. I took the car for a spin after removing this stuff yesterday evening but felt no difference while driving. Today I was bored an decided to go for a joy ride and to my surprise I noticed that my RPMs shot up to the true redline of 6000 RPMs while trying to pass a transfer truck.

I guess this insulation stuff was getting sturred up at the higher speed and eventually covered the air filter.which prevented airflow.

Is it possible that I didn't see any immediate results yesterday because the ECU needed time to realize that it's able to take a deep breath at the higher RPMs again?