Wierd 1986 300E idle problem
08-02-2008, 02:38 PM
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1986 300E
Wierd 1986 300E idle problem
My 1986 300e with 122,000 miles runs ‘normally’ when run every day. Especially when run 4 times a day. Problem only occurs after sitting more than one day – with no difference even up to six days.
After sitting those days, car starts perfectly and runs perfectly under fast idle. If you never stop it will run forever. But, if it is allowed to idle after approx five to ten minutes and BEFORE car even reaches normal temp – it will slowly begin to buck and miss at idle as if running out of gas and then quickly shuts down. (Running it to hotter temp makes no difference). It will then not restart for approx. 30 to 45 minutes.
Once it restarts after a little cranking, however, it will again idle not perfectly but well enough and begin to drive normally. Each time you restart it that day it will idle smoother and smoother and smoother and deliver you anywhere you want to go… as long as you don’t let it sit more than one day again.
(One can heel/toe gas and brake and keep car idling at 1500 in emergency)
Problems diagnosed by M/B mechanic so far: Lambda is 85% and is not sweeping and CO is not adjusting. Disconnect Oxygen Sensor or Idle Control Valve and Lambda will drop to 50’s. Once reconnected, however, Lambda will climb back to 85.
I am told Oxygen sensor appears to be working and acting normally when disconnected and then reconnected.
I am told Idle control valve appears to be working when disconnected and reconnected
2 year old Fuel pump measures a little over 6 amps.
OVP has been replaced with no difference.
Fuel pump relay replaced with no difference.
Spark pugs clean and perfect.
I would really appreciate any help offered.
After sitting those days, car starts perfectly and runs perfectly under fast idle. If you never stop it will run forever. But, if it is allowed to idle after approx five to ten minutes and BEFORE car even reaches normal temp – it will slowly begin to buck and miss at idle as if running out of gas and then quickly shuts down. (Running it to hotter temp makes no difference). It will then not restart for approx. 30 to 45 minutes.
Once it restarts after a little cranking, however, it will again idle not perfectly but well enough and begin to drive normally. Each time you restart it that day it will idle smoother and smoother and smoother and deliver you anywhere you want to go… as long as you don’t let it sit more than one day again.
(One can heel/toe gas and brake and keep car idling at 1500 in emergency)
Problems diagnosed by M/B mechanic so far: Lambda is 85% and is not sweeping and CO is not adjusting. Disconnect Oxygen Sensor or Idle Control Valve and Lambda will drop to 50’s. Once reconnected, however, Lambda will climb back to 85.
I am told Oxygen sensor appears to be working and acting normally when disconnected and then reconnected.
I am told Idle control valve appears to be working when disconnected and reconnected
2 year old Fuel pump measures a little over 6 amps.
OVP has been replaced with no difference.
Fuel pump relay replaced with no difference.
Spark pugs clean and perfect.
I would really appreciate any help offered.
