W124 500E M119 hard start- diode matrix ?

[ke6dcj]

It seems like the 500E is now having hot start problems.

The FPR is not leaking and holds vacuum.

After reading the LH Block Diagram (30-0010.pdf), and not wanting to spend for a new throttle body (engine wiring harness is NOT cracked), I'm going to throw some inexpensive parts at the problem:

Brake Switch: 001 545 01 09
Throttle/Idle Speed switch: 140 545 01 14
Air Temp. Sensor: 009 542 68 17 ( B17/7 )
LH Coolant Sensor: 008 542 45 17 ( B11/2 )

Another culprit could be the "Diode Matrix for engine speed increase".

Unfortunately, I cannot locate this part number, it's location is "V2" but from the diagram, I can't tell where to look.

I am also unsure about the LH coolant sensor pn#.

Together these should be under $100.

Wish me luck . . .

:-) neil

[Will_w202]

I have a similar issue I think, where the motor has begun having a rough, low, shaky idle for a few seconds after a hot restart. Doesn't seem to do this when cold. Any ideas? 92 500sl

[RANDY P]

My C36 did that hot start thing until I changed the MAF.

rjp

[Will_w202]

Interesting, although I spoke with a respected indie, and he says that symptom is not indicative of a maf. His response was, spend weeks trying to figure it out, pay us thousands of dollars to diagnose, or wait until the behavior gets dramatically worse, which it likely will in the future. Basically said consider it a quirk and live with it for now. His initial feeling was a fuel injector. I did just start running 100% gasoline (non-ethanol) 2 tanks ago. Perhaps it has dislodged some gunk in the tank.

[RANDY P]

Originally Posted by Will_w202

Interesting, although I spoke with a respected indie, and he says that symptom is not indicative of a maf. His response was, spend weeks trying to figure it out, pay us thousands of dollars to diagnose, or wait until the behavior gets dramatically worse, which it likely will in the future. Basically said consider it a quirk and live with it for now. His initial feeling was a fuel injector. I did just start running 100% gasoline (non-ethanol) 2 tanks ago. Perhaps it has dislodged some gunk in the tank.

How many miles on the MAF? I replaced mine due to drivability issues- car was dropping dead for no reason during operation.

It was as if someone turned the key off. Let it sit for 10 minutes or so and hot start was low idle, hunting all kinds of nastiness for a few seconds.

No codes present. Went through CPS, OVP, different gas from different stations, and then finally gave up and switched the MAF out and all symptoms went away.

Been perfect since.


Frankly, I would just leave it for now until the symptoms get worse and you can repeat them at will- you'll spend all kinds of $$$ at a repair shop chasing this ghost.

[Will_w202]

I don't have a record of replacement. Doubt it's 20 years old, but who knows. I'll sit on it til it gets worse, agreed. Thanks