Mercedes-Benz Forum banner

*Problem of the month*

1203 Views 14 Replies 6 Participants Last post by  teacher man
My car runs perfect when cold but after engine warms it does not accelerate correctly. A couple of people told me that it wasnt a mechanical problem since it runs fine but changes after engine warms.
I was wondering if the change in elevation was the culprit. I bought and drove the car from Seattle,WA to St. Louis,MO.
Because of this move do I have to retune the engine
1 - 15 of 15 Posts
+1 on Hunter
You list a 320SEL in your info. There wasn't a W126 320SEL. Maybe a W140 chassis?
I will have to go back and change my info. I have a 1989 560sec.

I dont think the FPR is the problem because I changed the FPR the fuel filter and both the fuel pumps two weeks ago (all new products from the dealer).

I do have a lengthy explanation if you car to read.

1. On May 2, 2008 I purchased and drove my 560sec back from Seattle, WA to St. Louis which is about a 2100 mile trip in which the car gave me no problems.

2. About a four months after I bought the car while I was driving for an hour-long period of city driving, a strange thing happened. For about a ten minute period when I stepped on the gas the engine would accelerate roughly sounding like a muscle car for the beginning stages of acceleration only. When I stepped on the pedal the engine would idle roughly only for about half a second and then respond normally. This only happened for ten minutes of the hour long trip and stopped happening during the trip and never happened since.

3. But after this strange occurrence my present issue started. Although the car idles smoothly and runs well it high speeds, when I push my acceleration pedal to the floor my 1989 560sec does not respond but if I lift off the pedal a little it responds. This problem only happens if I step on the pedal all the way to the floor. I'm not able to get maximum acceleration because the engine seems to flutter as if it does not know what to do if I push the pedal to the floor. I don't have to lift all the way off the pedal for it to start giving me acceleration but just lift off the pedal.

4. Strangely enough, this problem only occurs after the engine is warm. While the engine is cold I can get hard accelerations and the rpms go past 3500. After the engine is warm, movement of the rpms up to 3500 is slower and as it approaches 3500 it stops rising.
See less See more
How many miles do you have this might be key? Gosh it sounds like something is sticking. Does it only happen when you are driving or will it do it while in park as well? I am sure you have tried to do searches but maybe under "idle" or "acceleration". Wish I can help but not hearing or witnessing it is hard to diagnose. Keep it up here I am certain someone has been through it.
Have you cleaned the banjo bolt out lately? Back by the transmission dipstick. Here is a pictorial by the Benz guy.
Here is the link. apparently if this gets clogged you could have massive power loss etc.. Seems pretty easy to....

The car has 191,000 with a top engine rebuilt done at 160,000. After the engine is warm I cant get the rpms to go passed 3500 when I am driving or when the engine is at park. Ill try cleaning the banjo bolt and Ill get someone to help me put the problem on youtube.
What do you all think about the problem coming from the change in elevation? Could this be possible? Could the car just need to be timed for the change in elevation?
The difference in elevation between Seattle Wa and St Louis Mo, according to Google maps is only a few hundred feet at most so I do not think that is the issue. You said it will not go above 3500 RPM? Have you looked closely at the throttle linkage and cables? Is there anything that could be obstructing the movement? Something that could be checked for free.
You know what. I just thought of this. Get your cat converters checked. You could have a broken cat that is causing an obstruction in the exhaust. That could cause this problem after it gets hot. You could get universal cats welded on for cheap compared to the MB ones and at 191000 miles that may be the issue.
I did take it in to the dealer and they told me my cats were fine. I dont have any problem with normal acceleration or going up hills. THe problem presents itself when I do a hard acceleration only. THere is nothing obstructing my linkages.
Today I talked to a shop that said that it sounds to be running too lean. Something is telling the engine to run lean. On initial warm-up there is no problem because I lot of fuel is being sent. After warm-up the fuel sending is stopped because the outburst of fuel is not needed after engine warm-up. (Dont mean to sound like I know what Im talking about but this is what the shop said.)
What could cause this problem?
Running lean is usually a vacuumleak.

I would agree that sounds like vacuum if it is running lean.
Ill try spraying starter fluid to find the leak but I think that I might have to change the fuel distributor. I found another thread that describes the problems that Im having and he had to change the fuel distributor and that fixed his problem.
I found the problem. Thanks everyone.

I am very happy to say that I have my problem solved also.

I changed my fuel distributor and my problems are solved.

About six months ago I was at one of my favorite yards and I saw a flatbed bringing in what looked to be an SEL. How could I luck up and be one of the first ones to get parts off of this car. At a closer glance it was even the engine that I needed (a 560). As soon as they put the car in the yard I got the fuel pump assembly in the rear of the car, the passenger side mirror, the radiator, and the fuel distributor assembly. As I carted my treasure finds to the cashier he gave me a bill of $75. I happily paid this and took my finds home.
Today I put fuel distributor on in hopes that it would solve my problems and luckily it did.
After buying and driving my dream car from Seattle, WA I had the car for two months when my car stopped giving hard accelerations after warm-up. Although I could no longer get hard accelerations the car still ran fine on all other occasions. I spoke to other mechanics on-line and in person and also left my car at a dealership. All I got was a bill, advice to change my spark plugs (because they did not have any in stock), and an invitation to bring my car back so that more test could be run.
After finding this website and trying to work through my problems on my own (without spending money and dropping my car off somewhere) I finally found the culprit of my problem, the fuel distributor.
Thank you so much for helping me.
See less See more
1 - 15 of 15 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.