INTERMITTENT Dying after Startup!
 

My '88 300E has developed the old "no idle after start up." In the Bosch Fuel Injection troubleshooting chart there are several items that can cause this, and I will work though the test procedures for each one.

My question is; which one of the items could be INTERMITTENT? I typically associate intermittent symptoms with either loose connections or electronic circuitry.

The car starts great and runs great. Sometimes when kicking it in neutral to coast or to idle at a stop light it just quits. It will start right back up, but you have to rev it a little to keep it running.

This happens sometimes when cold, sometimes when hot.

I'm just starting on the troubleshooting process which is always a challenge when the problem is intermittent.

Thanks for any experience you might be able to share.

Air flow position sensor, is common for that description

Thanks DOC! The unselfish sharing of your experience has ALWAYS been greatly appreciated.:)

OVP or idle control hose vacuum leak?

The OVP resolved the issues I had which sound sort of similar to what you're experiencing (although on the m104 engine, not sure if that makes a difference).

The symptoms I was experiencing was that the engine would quit randomly while at idle (usually if hot from what I remember). However, it would occassionally have issues starting back up (i.e. starter would turn the engine but it wouldn't fire up).

I can't find a source for the airflow position sensor. I guess I'll call the dealer next.

I have been looking for vacuum leaks to no avail.

Last time I looked you had to buy the entire airflow assembly from MB to get the airflow pot. I found this knockoff part on fleabay (Item number: 330732912918) which also references the original Bosch number in the writeup. You can always do a google search when armed with the Bosch nuimbers or just take a chance on the knockoff part. Good luck. Mark

Thanks alot Hook! This might be the clue I need.

Have you put a meter in the X11 port? CIS might be telling you whats faulty? If it sits a % value and does not change than its throwing a fault.

The joys of M103 ownership...

Check the fuel pump relay.

Yes I have checked both of the diag ports for codes and nothing. I have an LED and switch box I made a number of years ago as well as a Duty Cycle meter, so I can check both.

Problem is that it is intermittent, so I have to catch it in the act. Like you I'm an EE. I've chased intermittent electronic problems for about 45 years. I would rather something smoked and burnt to a crisp than be intermittent. Much easier to find that way.:)

I haven't bothered because when it dies it is due to being requested to idle. It starts right up immediately and ran fine before. The odds of the fuel pump relay quitting only at those particular times are not very good.

Thanks for the suggestion though.:)

Does it just quit or does it kind of sputter out?

My 87 Audi 5000 did this to me for a while (same CIS-EIII fuel injection). Never figured out why :confused: I figured it was a failed check valve or something letting air get into the fuel system.

-J

Focus on a complete diagnosis. It's worth the time spent on a 103. Also, don't overlook the basics. It can put u right on the issue!

basic check 103
 

i would start with the fuses , replace all with fresh ones . A clean-up of all the pins on the OVP, FPR . and the idle switch pins may sort the problem or set a good base for next stage testing .
i sorted mine with a new FPR.

good-luck
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