I bought a 420 sel back in june. Actually it was really good deal. I paid 2200 for it. But it has few problems which i have been trying to trace to a right solution. I do have CD mannaul, but that does not include much of the trouble shooting section.
OK. Here is what one of the problem is.
a) Rough idle @ 1000 - 1200 rpm
b) Surge while driving. it almost seems like i am running on 6 cylinders instead of 8.
c) Lack of power.
Here following parts i have replaced
a) Distributor cap and rotor.
b) Spark plugs and ingition wires.
c) Fuel and air filter.
d) Fuel pressure regulator.
e) Checked the engine timing. Looks good
f) Checked the ingition coil. Test OK.
g) So far i have used like 15 bottles of injector cleaner.
h) Removed and cleaned the fuel injectors. Using proper procedure and used ultrasonic machine for ultimate cleaning results.
As you guys can see i have tried my best to solve the problem, but nothing seems to work. Also i read one of the posting mentioning about solder on controller.
which controller?.
Problem #2.
The rear heating duck does not want to close. Any clues how to close this vent?. The mannual does cover much on this topic.
And no leg heat on driver side.
[?]
1. high idle - usually the electronic module that controls idle goes bad. I had to replace mine.
2. injectors may still be clogged/dirty despite your use of injector cleaner in the tank. One or more might even be damaged. pull and see. Did you notice any of the spark plugs being fouled or very white? If they were all a light tan color on the electrodes, it's good.
3. lack of power and surging - you may want to check the exhaust system. My catalytic converters broke and clogged the exhaust. Took it to a muffler shop. They banged on the converter with a rubber mallet and we could hear rattling like a can full of gravel. Replacing the cats returned the car to full power.
I had some similar problem with my 420 and a smoke test revealed a lot of vacuum leaks. These cars are susceptible to this problem. Also, on the high idle, I just changed the control module only to find that the valve itself is sticky. Pull it off, hit it with 12V multiple time and you can hear the "clicking" becoming more authoritive. WD40 helped and now I need to get some carb cleaner and let it soak to finish the job.
Good Luck
Litton
'90 420 SEL
__________________
Litton
'72 280 SEL 4.5
'90 420 SEL
'98 ML 320
'86 560 SL
Hi
I forgot to mention. i did replace the ctl converter but it was used one and in good condition.
Thank you so much for replying. This is a awsome site for benz fans.
ajay
1. high idle - usually the electronic module that controls idle goes bad. I had to replace mine.
2. injectors may still be clogged/dirty despite your use of injector cleaner in the tank. One or more might even be damaged. pull and see. Did you notice any of the spark plugs being fouled or very white? If they were all a light tan color on the electrodes, it's good.
3. lack of power and surging - you may want to check the exhaust system. My catalytic converters broke and clogged the exhaust. Took it to a muffler shop. They banged on the converter with a rubber mallet and we could hear rattling like a can full of gravel. Replacing the cats returned the car to full power.
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