I have a 92 300e that occasionally stalls at idle after about a 10-minute warm-up. It will refuse to restart for approximately 20 minutes. Then it will restart fine but hesitates off idle and runs fine when RPMs get above idle speed. No dash lights are illuminated when the car is stumbling off idle and there are no trouble codes. After about another 15 minutes of driving it runs perfectly with no hesitation. So it runs fine when cold and runs fine after fully warmed up. Seems to happen if the car has been sitting for a couple of days. Last week it on a freeway off-ramp and had to get a push to the side to wait 20 minutes. I can definetly do without that experience again.

I've removed and resoldered the OVP, no difference. It is Hungarian and the larger internal coil heats up. That seems abnormal to me. I also checked on my 300te (which runs fine) and the OVP seems warm also.

What does the idle switch do? I connected a multimeter to the idle air valve (read 8v when cold, went down as the car warmed up) and watched as I activated the idle switch. I also removed the plug to the switch and directly bridged it. Nothing seemed to happen at the idle air valve, in other words the voltage didn't deviate. Is that right?

What's the best way to measure fuel pressure (I have two 300e's, so I'm fine with purchasing tools that are reasonably priced)?

Thanks,
Robert

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89 300te 222,222
92 300e 190,000

*bump*

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89 300te 222,222
92 300e 190,000

I just copied the last thread post to this;
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03-21-2005 09:38 PM
trants4md The good news is I have found the main problem, sort of! All you who assisted and said vacuum leak were correct. But where the leak is caught me off guard.

In tracking every vac line I came to the large line connector to the left of the throttle body air intake that goes into the intake manifold. Upon pulling the line and plugging the tap into the manifold my idle immediately smoothed out. The motor purred again! By this time the engine was warmed up.

Tracing down hose from there looking for a vac leak I tested every hose and connector under vac pressure. Every hose OK. Not a bad hose in the entire system. Then I reconnected it one section at a time. When the C4020-13554 Warn up regulator was reconnected it went ruff again and I had major engine hesitation on acceleration.

It appears that I have a vacuum leak internal in the warm up regulator diaphragm.

Does anyone know if a rebuild kit is available, or will I have to build my own diaphragm parts?

I am certain I can do something as the regulator is not staked together, but it never hurts to get a kit if possible!

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A medium rubber vacuum plug (1/4") lets you run this quick test to see if it responds!

The origianl thread is here!
http://www.peachparts.com/shopforum/tech-help/118279-started-no-power-when-cold-now-warm-also-post846283.html#post846283

trants4md
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85 500SEL
80 Leland TR7 Convertible
And Some American Stuff
94 Dodge Ram
93 Chev Lumina APV
79-81-83 Forzda

I'll try shooting some ether on the hoses and inspect them vacuum leaks. Do I have a warm-up regulator on a '92 M103?

Thanks,
Robert

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89 300te 222,222
92 300e 190,000

Read what Benzmac has to say in this thread.

M104 shuts down when hot

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'91 300-SEL

Robert,

Don't know the answer but am sure interested if you solve it. Have been a fellow suffering for 2+ years and although I've tried various remedies it's still not fixed. The symptoms you describe are so close to mine I already feel a bond between us . In particular the problems being only seen in that period post cold start but before fully warmed up, and most significantly, that 2+ days of inactivity cause the problem to be more acute, and never any trouble codes.

A couple of things to note though: (1) our cars are not quite identical – mine is ’92 but has the 104 engine which uses the KE-Jetronic injection system (CIS-E/EZL). (2) my problems are slightly milder than yours with a rough (hiccupy) idle being the norm, with an escalation to complete stall/20 min wait only occurring every 6 month or so.

Think I've read all the warm engine misfire/hesitation/stall posts on all the main MBZ forums, and have tried most of the proposed solutions - thus I have new plugs, leads, dizzy cap, crankshaft position sensor, OVP relay, fuel filter and air filter. I've also checked for air leaks, cleaned out the Throttle Body and Idle Control Valve (ICV), tested both the O2 and engine temp sensors and tried injection cleaner fuel additive.

There are more things on the list of people’s suggestions to try such as replacing the: coil, EHA, injectors, ICV, CIS-E, EZL, MAS, etc. but have been holding back mainly due to the expense. The thing that seems particular to me (now hopefully us) is the seemingly intermittent nature of the problem (car can run fine for several weeks) but that 2+ days of non-use consistently exacerbates the problem. My understanding is that these subtleties in our symptoms should let us rule out most of the proposed remedies.

Just recently in a post I received from a UK forum someone pointed me towards the charcoal canister that forms part of the EVAP system which was a completely new area to me. Reading up about this has lead me to look at the switchover valve and purge valve in the system – the interesting thing about them being that they only come into play when the engine warms up, intermittently cause air (fuel vapour) to be added at the intake manifold, and they are controlled by a vacuum (that I presume could dissipate over time – e.g. 2+ days!).

Not sure if I’m putting 2 + 2 together and getting 5, but on reading “trants4md”’s post to you I did start to get excited – not that I’ve a warm-up regulator either, but could I/we be suffering from a minor vacuum leak internal to one of the valves?

Going to have a good look tonight then the car will be left unused for 4 days over Easter. Will keep you posted if I find anything….

Regards,
Neil
Car: '92 300 CE-24 (LHD) cabrio

Thanks for your consolation Neil!

I've been out of town the last few days and haven't been near a computer...

I have two 300e's , one is a 92 and the other is an 89 (both M103). Now that the car has been sitting for a few days I'm going to pull out a bunch of parts from the *working* car, drive around until the problem manifests, and start swapping things. I worked in an auto parts store for a few years back in highschool and saw people spending lots of money parts they didn't need. I just can't get into that rythm with this car, especially since the dist cap is pricey. People would get new batteries, remanufactured starters and alternators and return their cores. We had a bench tester and probably 50% of the cores were in perfect working conditions. Dist caps can last a long time, so can wires and plugs (besides, I just can't see those causing this problem).. I might throw a new rotor in there, and maybe a fuel filter.

I do believe it is a fuel starvation issue, but not positive. I just received a digital mutlimeter (DMM) with an interface to my laptop. I'm going to connect the DMM to the idle control valve, temperature, EHA, and CIS-E diagnostic port and observe/record the various values and see how they change when the problem appears. The next diagnostic I'll be after is fuel pressure, though not sure of the best approach there...

Should take a few days to find the time and get the diagnostics set up.

Robert

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89 300te 222,222
92 300e 190,000