300te stalling when warm in idle and start up

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Ali_Boz
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300te stalling when warm in idle and start up

Post by Ali_Boz » Wed 09 Mar, 2016 5:43 pm

Hi,

Long time reader, first time poster

I'm having an occasional idle and warm start problem with my '91 300te (M103.983). Once the engine is going on the road it runs very smoothly and can barely hear it at the lights. Its fine on a cold start too but when the engine is warm it can be difficult to start it strongly again and will often start and rpm will fall too low and stall within a second. This often leads me stranded in carparks for a good 10 minutes or so. The engine will often stall in carparks when I'm not using the throttle and a few times under braking when in 'D', and will stall in 'R' in carparks. However I've also noticed a slight lingering smell of fuel I presume outside the engine when its running (had my exhaust fixed but still have a smell). I have taken the ICV out gave it a good clean and the hoses looked in good shape.

When it idles well its sits at just over 500rpm in D and just under 1000rpm in P, N and from the cold start. From what I know that seems pretty normal. I've done a bit of research on this but for my specific symptoms I don't know what the problem is or how to fix it. I hope that this is just an easy fix.

thanks.
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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Re: 300te stalling when warm in idle and start up

Post by AMG » Fri 11 Mar, 2016 2:31 pm

do a search for fuel accumulator - this is often a problem with hot stalling issues.

Also, occasionally the lack of pressure in the delivery line can cause the fuel to evaporate. Not often, but it can happen. sometimes this is indication the fuel pressure regulator or sometimes referred to as 'damper' is on it's way out. check to see that your fuel hoses are correctly routed also. Som info in the reference library (CIS-E)

accumulator is located next to fuel pump(s).
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Ali_Boz
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Re: 300te stalling when warm in idle and start up

Post by Ali_Boz » Tue 15 Mar, 2016 1:54 pm

thanks for the tip, i'll have a look around and do some more research.

In further checking the spark plugs and Oxygen sensor were all carbon fouled and will need to be replaced so I now know the engine has been running rich. I then checked for any fuel leakage from the EHA but it seems fine and so do the o-rings.

thanks again!
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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benzy53
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Re: 300te stalling when warm in idle and start up

Post by benzy53 » Thu 17 Mar, 2016 12:00 am

When your engine is warm the whole system is working that means a lot of testing
Engine at operating temperature starting and idling issues
1. Check fuel pump
2. Check for air leaks
3. Check if cold start valve is not leaking
4. Check CIS injectors
5. Check temperature sensor
6. Check voltage at EHA
7. Check the pot at air mass meter
8. Check O2 sensor
9. Make sure you have a reading of 45% to 55% when measuring with a duty cycle reader at pin 2 and 3 and it MUST fluctuate by 5 -10 %
If you haven't a duty cycle reader just use a multi meter, put it on DC V and the reading should be 6.7 to 7.5 V
I believe that keeps you busy for a while. I had the the same problem and it was the O2 sensor. Also make sure your throttle body is SPOTLESS
and check if sensor at the throttle body is working. It must recognize the fully closed and fully open position.
If that doesn't help we have to go into it a little more deeper, please let me know.

benzy 53

Ali_Boz
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Re: 300te stalling when warm in idle and start up

Post by Ali_Boz » Fri 18 Mar, 2016 5:07 pm

thanks benzy53 ill keep you posted as I run down the list when I have the time!
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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benzy53
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Re: 300te stalling when warm in idle and start up

Post by benzy53 » Fri 18 Mar, 2016 9:44 pm

Hi Ali
I read your initial post again and noticed the fuel smell. This puts the fuel system on the top of the list.
If you have a rapid pressure drop, the result is formation of bubbles in the system.
Check KE injection systems for leaks. The best way is to do a pressure test. To do this turn the ignition off.
Connect the pressure tester where normally the cold start injector feeds in. Remove the cold start relay and bridge
point 7 and 8 to enable the pump to run. The pressure must be between 5.3 and 5.5 bar. Is reading to low check the output
of the fuel pump. Is the reading to high disconnect the fuel return line from the fuel pressure regulator. Is reading now
correct, the return line is blocked. Is the reading still wrong the FPR is maybe faulty. Regarding FPR: diconnect the
little rubber hose and see if any fuel is coming out ( FPR gone ). Also make sure that rubber/plastic line is not
blocked, other wise the FPR cannot work proper. Remove the bridge between 7 and 8. At this point the pressure drops below
the closing pressure of the injection valves to about 2.8 bar. After 30 min the pressure must be at least 2.5 bar,. Before spending any money
you can check a lot by just observing and following the fuel line from the tank right up to the injectors.
Another " rough " test is to depress the air meter plate in the morning, you should fell the same resistance
as when you turned the engine off the night before. This is only a partial test.

Good luck, benzy53

P.S. I had a lot of issues with my 1990 300TE and I know how its like. The good news is it can be fixed.

Ali_Boz
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Re: 300te stalling when warm in idle and start up

Post by Ali_Boz » Sun 20 Mar, 2016 9:18 pm

cheers benzy! thats more depth and detail than I could've ever hoped for. When I find the time ill let you know how I go with it.

this is my 2nd 300te and this earlier M103 has been more trouble (to an extent) than my previous M104 2.8, go figure haha
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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Re: 300te stalling when warm in idle and start up

Post by Ali_Boz » Fri 29 Apr, 2016 8:36 am

UPDATE: IDLE ISSUE RESOLVED!!!

faulty idle control valve!! has been replaced with a new one and car idles great. previous one was disconnected an car idled fine

thanks for all the help, i've learned a lot!
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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Re: 300te stalling when warm in idle and start up

Post by Ali_Boz » Wed 31 Aug, 2016 3:31 pm

UPDATE !!!

I'd like to retract my previous post as with the brand new bosch idle control valve installed car not experiences a higher than normal idle in P (just above 1000rpm even when warm) and surges/ hunts between 1000-1500 rpm when rolling at 60km/h. when unplugged car runs perfect, just a bit sluggish from the lights then comes alive.

I've readjusted the lambda ratio with a multimeter achieving an average 50% in the duty cycle from the previous 75% so it was running quite rich. so with that leaned out the car has improved greatly at its take off.

could this idle surging be the result of a possible vacuum leak, a throttle issue or a wiring problem? just want to reiterate that the car idles fantastically when ICV is unplugged and worse when plugged in

sorry to be annoying but thanks
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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Re: 300te stalling when warm in idle and start up

Post by MMWA » Wed 31 Aug, 2016 7:07 pm

high idle on on my 300e-24 was caused by a worn out airflow sensor pot.

Plenty of documentation out there on how to test it for smooth operation across its entire swept travel with a multimeter. Anything over 180k km and its pretty much assured to be rooted, mine was.
MMWA

Ali_Boz
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Re: 300te stalling when warm in idle and start up

Post by Ali_Boz » Thu 01 Sep, 2016 10:09 am

great ill research into that thanks, and yeah look at 373k im sure it'll be on its way out.

ill keep you posted
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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Re: 300te stalling when warm in idle and start up

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Re: 300te stalling when warm in idle and start up

Post by Paps254 » Tue 01 Nov, 2016 9:02 pm

I have a similar problem with my 300E (2.6)

When I start the car in the morning, it starts first time with no issues. After driving for a short period and the car gets to temperature, the following problems can occur;
(i) When in traffic or at a stop light, the car revs can begin to stumble up and down and then stall. After it stalls, I cannot start the car, it just cranks over and over again. I have to wait for the engine to cool down (usually 30-45 minutes) and then it will start.
(ii) After driving for some minutes and the car gets to temperature, If I stop the car (like going from home to work), If I start the car again while engine is warm, the car will hesitate to accelerate and can stall. I usually have to put the pedal down so it does not stall.
I have had the same problem since I replaced the engine 3 months ago. I took it back to the garage but they couldn't pin point the problem. I replaced the OVP relay but the problem has not gone away.

Any thoughts?

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Re: 300te stalling when warm in idle and start up

Post by Ali_Boz » Wed 09 Nov, 2016 11:50 am

I have a similar problem with my 300E (2.6)


yeah well my solution to the problem wasn't a complete fix but my indi mechanic unplugged the idle control valve as he thought it was faulty. he adjusted the idle and it run quite smoothly. but when i came around to replacing it there was a different idling problem that I haven't fixed yet. i must have a throttle sensor or switch problem or a vacuum leak.

just to the usual checks like plugs, leads, dizzy, rotor and make sure they're all clean. check your fuel pressure regulator my research has shown that when these play up they present in the symptoms you're experiencing.

good luck!!
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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Re: 300te stalling when warm in idle and start up

Post by Ali_Boz » Sat 08 Apr, 2017 10:09 am

UPDATE:

finally got around to putting in a new air flow potentiometer in after waiting 6 weeks for delivery from china. yes the part was only $20 but if it lasts 12 months i'll be happy to replace it again.

car now idles like it should both when hot and cold and drives very nicely

thanks for everyones help :occasion5:
1991 w124 300TE
1993 w124 300TE 2.8 R.I.P

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