89 300E, Rough Idle, hard start, stalling solved, thank you all

[rayhalks]

Thank you to all that helped out with my 89' 300E idle, start, stalling problem.

I will outline all that I did in the hope that it helps someone else, I spent over 12 hours
working on it and hours reading on the net.

Here was the problem:

89 300E, 62K, regular service:
Car started hard, hot or cold, need to give it gas to keep it running. Then once I put it into gear it wants to stall. Once it was running, say a mile or so, car was fine. I started having this problem when my dumb head put 87 octane in it. Since then I have ran cleaner and 5 tanks of 93. Still was happening. I start the car it runs real rough, shaking at idle and at 3000 RPM for a minute then once I take off smooth. But when I come to a stop, it idles a little eratic, 500 - 700 rpm, almost like the AC is kicking in, but it is not.
Anyway, it seams to get worse with the more days that go by.

More: Violent, one time, shake on cold start is a product of a low idle.
When the car stalls in D while driving and then stopping is a result of low idle. It drops to 600 RPM at a stop then will just shut down, like I turned the key off, no rough idle then stall. I simply double foot it and gently press the accelertor to maintain 600 RPM.
It starts easily but idles rough, need to flutter the accelerator to keep it going then brake and accelerate at the same time to put it into Drive or Reverse. Once rolling though, from 600 RMP and up, the car runs great.


OK, here is what I did, in sequence.

- Replaced Distributor and Rotor since it had some erotion in it. Didn't help much.
- Went to Bosch Platinum 4 spark plugs. Didn't help much.
- Tested ignition wires. Fine.
- Cleaned throttle body and butterfly. Helped idle some.
- Tested OVP relay. Tested fine.
- Checked all vacuum with Starting fluid, found hose off Fuel Regulator Valve to Air cleaner housing, easy to accidentally disconect
if not carefull in removing the air cleaner. Check this!
- Tested O2 sensor. Tested fine.
- Ran Chervron Techron complete fuel cleaner. Helped some.
- Replaced fuel filter. Helped a little.
- Cleaned ICV. Helped start problem.
- Cleaned the fuel injectors offline. Smoothed idle out some.
- Adjusted Idle up a hair. Helped start and smoothness.
- Lubed all the throttle linkage and springs, it appeared they were sticking a little causing idle to be eratic some. Helped some.
- Adjusted CO adjustment. With all above and this the car runs perfect.
Starts cold/Hot fine now, idle in P, D, D w/AC, etc. at 600-700 RPM. No
more surging, stalling. Can't tell car is started when at idle in D.

All the above is outlined in various places in this forum, so search for it.
All of the above was just routine maintenance that was needed. Just
bought the car a month ago but with 62K it sat a bunch. 3 last things to check,
for that I see can easily occur: Check for fuel leaks, especially at the
filter and fuel pumps. Check to make sure fuel pumps humm and function, this includes
checking fuel pump relay. Check your injectors offline. On my car they were
part mechanical assist and on one the ball valve was not seating properly causing
a injector leak.... this contributed to hard cold start.

My problem was a combination of things, all stemming from what I believe was crappy,
dirty fuel. Car sitting a bunch before I got it.

Hope this can help someone as you all helped me!
Happy driving![:D]

[bisser01]

man this is the best post ever! there is alot of 124es that are with idle problems its a major problem.
by the way talk to my frend in germany he works in daimler and he said that for the older cars the simple spark plugs are better so i tuke the 4res out and tryd the 1nes bosh just to test if dhere was a diference well let me tell you he was corect the reason was that the 4res are spiting the electricety and they dont burn as well im back on the 1nes bosh it runes a lot better.hope this helps ,anyway if someone has a diferent opinion about the spark plugs please pot it and any other problems with idle.

hope this foum gets big,allot of idle problems out there w124

[rayhalks]

Bisser01, thanks. I had to fumble through hours of reading to get it but saved me a bunch. Just for giggles I stopped at the MB Dealership to ask them their opinion. Didn't tell them it was fixed already and they told me it was 90% the fuel distributor on that car. Yeah! If I want to throw 2K away, I know better ways......lol

Anyway, I've read that these older MB's like to run rich. And when your running rich and at lower RPM's around town (these cars are meant for 3000RPM + so I drive in low around town), the spark off the spec plug may be impeded by rich gas. This is very similiar to my old shovelhead and panhead Harley's. I run hotter plugs to keep them from fouling. Gotta be careful though not to run to hot of a plug and burn a hole in the top of the piston, have seen this on harley's. Anyway, I'll swap to my old plugs once I get a fuel economy reading from the fixes of the car. Then I'll swap and get a reading again and compare performance and economy between the two since I already dropped the 40 bucks for the BP4's.

[rayhalks]

As an update, I passed my emissions test today.
Finally I can get plates and get rid of the temp tags.
Also, don't know if it was checking all connections or the crappy low idle performance but my cruise control works.
Now it all works, even cold A/C.

[GHM]

Glad to hear your up & running again.

[Cyberbach]

Please excuse my ignorance but what does this mean - "Checked all vacuum with Starting fluid" - How do you check vacuum with starting fluid?

[lazuli]

first off i want to say that this kind of post is what the forum is all about in my opinion.

being a moderator i read all the posts and i have to say this is one of the most helpful i have seen. i can see that you spent a lot of time on this issue but i am sure that you enjoyed it. i also enjoy working on my mb not only saving big money, but getting the job done right. i have been undoing five years of shoddy repairs on my current vehicle ( '89 300te 200k mi ) and now have it running perfectly thanks in large part to this forum....

also my brother-in-law ... who showed me the starting fluid vaccuum check: if you spray a fine mist of starting fluid or similar around the vaccuum lines where they connect or where you suspect a leak, the engine will rev a bit when the fluid mist goes through a leak

good luck and thanks everyone

[GHM]

A job well done. Lets keep this forum rolling. Precise and educational

[GHM]

One more other thing. I have totally repaired my vehicle and it now runs like it should all due to the posts that I have read since joining. Thank you again to all the replys and posts. Good Luck & Good Driving

[neanderthal]

the platinum plugs are designed to be used with high capacity/ discharge ignitions sytems as found on modern cars. you are NOT doing yourself any favors by using those.

just a thought.

but congratulations on logically and methodically attacking and solving your problem.