89' 300E Hard Start, Stalls occasionally at stops, eratic idle - Benzworld.org

rayhalks · 09-22-2005, 06:37 AM

Hello All,

I have read alot of threads regarding this and have checked alot of this out.
89 300E, 62K, regular service:
Car started hard, 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. So I checked the car out. New plugs, distributor and rotor, checked plug wires - fine. Then I noticed that the vacuum hose was pulled from the fuel regulator valve, hose that goes from rubber house of air cleaner housing to valve cover. Reconnected that. Now when 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. I then came home and checked the OVP. I unplugged it and started the car. Car Started the same as it did before when hot, but cold start I couldn't get it started. Plugged the OVP back in and the started cold and started but same as the above problem. I then notice that the CO adjust on top of the throttle body, the long aluminum column that goes up into the air cleaner housing, had some weird drill marks near the top. The housing itself has a crack in it. Does air come in this housing or is it just for the hex screw adjust. When I put a hex down it it pushes down on the butterfly but I can't seam to turn the screw. What size hex is this?
Anyway, it seams to get worse with the more days that go by. Definetly worse once I repluged in the vacuum to the fuel regulator.
Any suggestions will be appreciated. I will post the solution once I find it also. thanks

GHM · 09-22-2005, 07:11 AM

The hex size is a 3mm ball tip. Gentle push down until it engages into the head and carefully adjust if you are sure of what you are doing. Left is lean and right is rich. The column you made reference to is to the adjustment screw, apparantly some are sealed and some folks gain access to it by drilling a small hole to remove the small ball bearing inside to reveal the adjustment screw. Check your motor mounts as well as I had similar problems intially with my vehicle.

rayhalks · 09-22-2005, 08:08 AM

Thanks for the info on the CO adjust.
I should of stated in my earlier post that the violent, one time, shake on cold start is a product of a low idle. It never did it until I reconnected the fuel regulator valve vacuum hose yesterday. I have checked for vacuum leaks and when I spray starting fluid under the air cleaner cover it goes up in idle some and idles great for a minute then back to eratic. Is this due to the crack in in the CO adjust housing. Is this crack a source of vacuum leak? It seams I fixed one problem and really exposed another.
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.

GHM · 09-22-2005, 10:58 AM

What I'd suggest go thru the forum and check similar syptoms that you are describing. That is what I did and the recommendations help my vehicle to run properly again. The motor mounts replacement seemed to help me tremendously. I have cleaned all (electrical cleaner)the contacts on all the relays as well. One other thing is to check the fuel filter as well. Just one more thing when I purchased my vehicle
I when thru everything that I could you know DIY's

So good luck and good driving

rayhalks · 09-22-2005, 11:01 AM

Thanks, I will continue to troubleshoot.
One thing I noticed is that this morning I fueled up with 93 and some fuel injector cleaner and at lunch the car idled great around town, no stall. Was still a little rough at start.

Does fuel injector cleaner lean or richen?

GHM · 09-22-2005, 11:05 AM

All I know it took several cans of Techron to run thru my system before I got the results I was looking for. As far lean or rich I know it cleans thats it.
I finally changed all my fuel injectors with a marked improvement in performance as well