HELP! Tach dead, weird throttle response and shifting... WTF?
(I posted this in the W124 forum, but since the 500E has more mechanical similarity to the 500SL under the hood than it does most all the E-Class cars, I thought it might be appropriate to inquire here as well- pardon the intrusion!)
Hi all,
Hopefully someone can help me diagnose a problem. This morning when I started up to go to work, I noticed very weird and delayed throttle response from my 1992 500E. I had to push the accelerator down much farther than usual, maybe 40-50% of the way, to get any response. I looked down and saw the tach was inoperative. The car was shifting very strangely, perhaps a limp-home mode? And as I got on the freeway, I found the cruise control was also inoperative. The speedometer and other gauges all are working fine. No ASR light, no check engine light, no warning lights of any kind! All fuses in the fuse box (in front of the brake master cyl.) appear fine. Is there a different fuse box anywhere? The owners manual makes no mention. Idle speed seems a tad high, it is mostly steady but will drop and then rev back up every 30-45 sec. it seems. Without a tach it is hard to say what it is actually idling at.
I had removed the air cleaner assembly last night to replace the temp sensor for the aux. fans, but it drove fine for the 30 miles (and several restarts) I drove afterwards last night. I wondered if I could have disturbed something under there, but don't know why it would have been a delayed reaction before the problems started.
Does anyone have any ideas? I do not know where to begin looking. I would much rather try and diagnose this myself if possible, rather than taking it to our local dealer, who sucks...
I had a similar issue with a e240 1998 model. limp home mode thats what the mercedes dealer called it. if i remember right it had to do something with the airbox. or a sensor on the airbox? or airmass sensor? half an hour and 600 dollars later the car was better than new. good luck.
the part was the most expensive thing. it looks like a plastic cilinder about 15 cm in diameter and has a plug that plugs into the outside of it. i think they called it the airmass sensor. sorry i'm brain dead when it comes to mechanical things. i hope this has helped you more.
Thanks for the info... If I remember correctly, the 1992s did not use a mass airflow sensor to measure incoming air. Someone correct me if I'm wrong!
Oh, I also noticed the A/C was not engaging when I drove it to lunch (has worked perfectly until now).... and NOW the ASR light is on on the dash!!! Jeez...
(I posted this in the W124 forum, but since the 500E has more mechanical similarity to the 500SL under the hood than it does most all the E-Class cars, I thought it might be appropriate to inquire here as well- pardon the intrusion!)
Hi all,
Hopefully someone can help me diagnose a problem. This morning when I started up to go to work, I noticed very weird and delayed throttle response from my 1992 500E. I had to push the accelerator down much farther than usual, maybe 40-50% of the way, to get any response. I looked down and saw the tach was inoperative. The car was shifting very strangely, perhaps a limp-home mode? And as I got on the freeway, I found the cruise control was also inoperative. The speedometer and other gauges all are working fine. No ASR light, no check engine light, no warning lights of any kind! All fuses in the fuse box (in front of the brake master cyl.) appear fine. Is there a different fuse box anywhere? The owners manual makes no mention. Idle speed seems a tad high, it is mostly steady but will drop and then rev back up every 30-45 sec. it seems. Without a tach it is hard to say what it is actually idling at.
I had removed the air cleaner assembly last night to replace the temp sensor for the aux. fans, but it drove fine for the 30 miles (and several restarts) I drove afterwards last night. I wondered if I could have disturbed something under there, but don't know why it would have been a delayed reaction before the problems started.
Does anyone have any ideas? I do not know where to begin looking. I would much rather try and diagnose this myself if possible, rather than taking it to our local dealer, who sucks...
Thanks,
Brian Flanagan
Need More info.
Why did you have to replace the aux fan switch.
If I am not mistaken the aux fans are controlled by the switch located at the A/C
dryer/ accumulator.
There is a temperature sensor on the engine .
I think on your car that goes to the mas/ fuel pump module.
Before you go further put back the old one and see.
May be you installed the wrong sensor
I hope you don't have problems with the mas module sins is expensive.
The Mas / fuel pump module, gets the signal from the rpm gauge And on some cars the oil pressure gauge/ or both.
If car flips over no rpm/oil pressure , Mas /fp module shuts engine off
I bought a Cool Harness- K6JRF Auto Page , scroll down just a little from the top of the page- I had heard good things about this guy's products, it just kicks the cooling fans on at a bit lower temp. Worked as advertized, and I do not think that is the source of the problem, I just mentioned it to give the reason why I had the plastic cover off. But just to be sure, I unplugged it, and saw no change, all problems still present and accounted for!
And I was confused about the airflow meter, there is a hotwire unit right there on top, plain as day!
Thanks again to everyone for all the suggestions!
-Brian
Linear Mode
