'86 300E rough idle - PeachParts Mercedes-Benz Forum

bigschot · #1 07-30-2003, 07:58 PM

My '86 300E has 160k miles on it. After sitting unused for a couple of years, I started driving it again about one year ago and have had serious, ongoing driveability problems. I have replaced - or have had replaced - the following parts, but still have a minor idle problem and more recently difficulty restarting after it's warmed up (and a strong gas smell when it does start):

- Fuel pump (new Bosch), fuel filter, and pressure regulator
- Injectors incl. plastic sleeves, fuel distributor, and rotary idle actuator
- EHA valve, overload relay

All the obvious things like plugs, wires, rotor, cap, etc. are new or close to it.

Cylinder head was completely rebuilt at 145k; compression is +/-175psi in all cylinders; oil consumption is minimal; mileage is consistently 22mpg. Aside from the problems mentioned above, it runs great (after replacing all those parts).

I'm far from a skilled mechanic, particularly at diagnosis, but I have figured out how to replace lots of parts.

The dealer I took the car to, MB of Princeton, was beyond useless.

Any suggestions on what I should try next?

Thanks,

Gary

mike690003 · #2 07-30-2003, 11:56 PM

Buy a bottle of Chevron "Techron" fuel treatment from the auto parts store. It might be moisture in the tank from those years of storage. If that doest work, keep us posted.

bigschot · #3 07-31-2003, 12:06 AM

Thanks for the suggestion. I tried Techron and a couple of other products. They made no difference. Also, I forgot to include in my original post that all vacuum leaks were taken care of as well.

Gary

mike690003 · #4 07-31-2003, 12:31 AM

As a matter of fact, my car exhibited those same symptoms. I had two problems:

1. One of my spark plug holes in my engine block was not enabling the spark plug to tighten. I had to buy a "Helicoil" insert to fix it.

2. My spark plugs were tightened, but were not tightened enough.

My car is still running rich, my air/fuel mixture is off.

I also had the my new spark plug wires tested, my #2 wire was defective and not providing enough spark. I had to buy another set (long angry story).

Get a new air filter and clean the throttle plate.

Keep us posted.

#5 08-01-2003, 05:52 PM

Do a search on "air mass potentiometer," you will see that this is what your problem most likely is. You do need to somewhat understand a multimeter and how to test, but that will get you started.
Tim