Please help with strange problem! - PeachParts Mercedes-Benz Forum

BigMikeT57 · #1 12-15-2003, 03:22 PM

A friend with a '87 420SEL w/170 kmi, has had two of the same
occurances in two days.

Says car is acting fine. Stops at a streetlight/stopsign etc., no problems. When he presses down on the accelerator the car just
idles. Moves along at idle.

Thought it might be tranny at first, but says the tach is at steady idle, not revving up with accel pressure.

After a minute or two it is back to normal.

Any ideas?

I tried the search, but this seems way out of the norm.

Thanks in advance.

sbourg · #2 12-15-2003, 04:05 PM

First thing I would check is the accelerator linkage. The throttle may simply not be opening. Second check would be the airflow meter plate. If it is sticking, it won't open and let more air past when the throttle is opened.

Steve

BigMikeT57 · #3 12-16-2003, 01:44 PM

Steve,

Thanks for the suggestions.

I had thought of the linkage, but not the airflow meter plate.

I'll pass it along.

pesuazo · #4 12-16-2003, 02:48 PM

Read my post on "Please read-long-smog test-limp mode".
I was experiencing exactly the same problem on my trip from NY to NC. It sounds your friend's car is going into limp mode.

BigMikeT57 · #5 12-18-2003, 10:49 AM

Thanks Pesuazo,

All the posts that I've read dealing with "Limp Home" mode (except yours) have been for '92 + cars.

I didn't know the 126's had that feature.

pmckechnie · #6 12-19-2003, 07:34 AM

I had this exact problem on a customers 87 420SEL. On his, it turned out to be the throttle plate was sticking in its bore. It is a round plate in a round bore and is adjusted at the factory to close completely without binding. As everything wears and gets dirty, it will stick. The linkage has one rod (I think it is at the back of the engine) that has a spring in it so if something hangs it wont bend anything. This rod is only a safety device and I only mention it so you and understand how the peddle can go down but the throttle plate not open. If you follow the linkage to the front of the engine and see where it goes down , you will see where this throttle plate is located. With the aircleaner removed, carefully press down on the big round air valve. Look down and torward the front of the engine and you should be able to see the throttle valve. Spray this plate with carb cleaner, stoping every so often and start the engine so it won't get flooded. If this helps temporarly but starts hanging again, then the throttle valve will have to be removed and adjusted. This requires removal of the fuel dist assembly.

Good luck.

BigMikeT57 · #7 12-19-2003, 08:24 PM

Paul,

Thanks for the advice.
I will pass along the info to my friend.
This sounds like a very likely scenario.

Regards,

haasman · #8 12-19-2003, 10:20 PM

I had a similar problem but with a twist-

Years ago, I bought my first Mercedes, a 280SE. Really liked it, did well, a good used car while it lasted. But one day it would barely start, idled so-so but regardless of how I tried to apply the gas, it wouldn’t move.

I checked everything I could think of. I went to a second level of investigation- I took the air cleaner off and noticed the air sensor wouldn’t move down. I could grab the nut carefully in the middle and it would rise, but wouldn’t move down! Very strange.

With horrible visions of $2,200 fuel distributor in my mind, I started to look very closely. Underneath the air mass plate was a thin washer, stuck to the underside. I used pliers and grabbed it. One edge of this very thin washer of about 11/2” diameter was slightly bent.

I was shocked on two accounts: This damn thing has been whipping around in the intake! And could this washer have actually stood on end, prevent the air sensor from moving down?

I started the car and it worked normally! Wow. Talk about good fortune. Sometime in the car’s past this washer had gotten into the intake.

I still have the washer taped to the front of my tool box. Very few people understand why.

Haasman