Hello my-1986-300E has a problem when engine is a normal temp if i turn engine off and restart 5 minutes later when i press the gas pedal to go the engine chokes for about one minute or two engine goes back to normal after the two minutes parts i replaced ovp-pot-roter cap plugs f filter 02 sensor f injectors accumulater cooling sensor And the air fuel mixture is around 50% Thank you for our help Tony

Did you use copper plugs or platinum?

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe

I have tried copper plugs now have platinum plugs at runs a bit better

Go back to copper bosch copper sparkplugs. And take it from there.

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

I agree, the 103 really does go much better with a copper plug. Platinum makes the 103 act very strange...

Hmm..Been struggling with this same problem: car stutters right before switching over to closed loop. Plugs ain't the problem, I can tell you that. Its something in the fuel system. Coolant sensor?

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

It sounds fuel related. Did you clean the idle valve and fuel pressure regulator?

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J.H.
'86 300E

iam going to give the copper plugs another try thank you pesuazo for your help tony

if i get my car to run the way it suppose to i will let you no and i did replace the coolant sensor tank you fahrgewehr2 tony

i will try the fuel cleaner and i did clean the idle valve but not the fuel pressure regulater iwill do that next and iam going to have the fuel pressure checkd tank you j. HIDALGO for your help tony

The issue is not "copper versus platinum", but resistor versus non-resistor. About the only reasonably available OE type non-resistor plugs are Bosch Supers, which are available in both resistor and non-resistor versions. Make sure you get the non-resistor version specified in the owner's manual, which should be H9DC. Don't buy HR9DC. The "R" indicates a resistor type plug, and almost all other comparable plugs, including popular "platinum" replacements such Bosch Platinums, are resistor type.

Resistor type plugs may cause increased idle roughness and emissions, but the evidence is mostly anecdotal.

Notwithstanding the above, I don't think the problem here is spark plug related.

Duke

you right Duke i replaced the plugs today and no change i use the H 8 DC BOSCH SUPER tank you Duke for the info tony

Check for hard hoses on the idle control valve, and for any other vacuum line leaks -- I'm guessing you also have some throttle lag on takeoff, hot or cold.

Also check the idle control valve for proper funtion, it if sticks you may have trouble.

I'd also clean the venturi on the fuel distributor and check for smooth movement of the air metering flap hot -- if the seals on the plunger are bad, or the plunger is scored, it could hang at idle, causing funny air fuel mix.

You could also have a bad throttle position senor pot. This will cause the same problems as a bad accelerator pump -- no reponse on throttle opening for a second or two.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Well Tony, you have inspired me to get get off my butt and fix this problem on my SE. Been living with it for a year now

I'm thinking this is a lambda problem. Like the car is in "lambda limbo." Something is hanging up when the systems electronic control comes into play. During this time the incorrect amount of fuel is being metered. Just my theory, and I am open to all suggestions.

Can someone explain exactly what happens during this transition (open to closed loop)?

A question Tony- Do you experience this problem when you first run the car during the day and it gets to about 60degreesC? I get a weird surging on the road for about 45 seconds.

Mike

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

My highly simplified understanding is that the during warm-up the coolant temp sensor is sending a resistance value to the control unit, decreasing as the engine warms. The control unit considers that along with air flow and throttle position, and tells the EHA how much to enrich. When the coolant temp hits 80 C - "cutover", the resistance has fallen to the point where the control unit is programmed to accept input from the O2 sensor and uses that to fine-tune the mixture.

Cutover might be sooner if you have a heated O2 sensor.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe