I just replaced the sparklugs and it seems that the car does not iddle smoothly as before. I stay around 800rmp for 10 sec then drops to 500rmp for 2-3 sec then back to 800rpm again. As the rpm drops the 2 fans in front of the radiator go On but go off then the rev. climbs. My question is, can the new plugs cause this irratic iddle? Or something else? BTW I used copper core plugs made by NGK. Any suggestion is greatly appreciated.

Larry
'92 190E 2.6 103K

Not sure on that model, but it does sound like some of the weirdness the OVP relay can cause.

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

Hi again,

How do I check for this OVR? Is this procedure involed or can it be easily repaired/replaced? I read somewhere in the past that jumping starting can damage the OVR. The last time the car was jump started was 1 yr ago, but I just noticed this erratic iddle right after I replaced the plugs.

-Larry

If it ran fine until you replaced the plugs, that would be the first thing to "double check"
1-are you certain all the wires are on the correct plugs?

2-Did you take care to remove the plug wires by (using special plug wire pliers) or pulling the connector itself, and NOT by pulling on the wire?

3-did you set the gap or check the gap before installing them?

4-did you drop any of the plugs before installing them?

Please don't be insulted by my questions. It isn't that I think you don't know how to change a few plugs. I'm just trying to make sure you didn't accidentally create a (miss or) problem without realizing it.


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Be sure that you used the right plugs. Only copper core plugs will do, no plats.

Thanks,

I did use copper plugs, checked the gap, but did not use a special tool to remove the wires. I changed one plug at a time so pretty certain that did not mix them up. I rechecked the wires making sure that they're tight and this probably was the culprit. For the last 2 days the car iddle fine at a steady 750rpm. I'm still confused as to why the fans come On and Off? Thanks for everyone comments as always.

-larry

Had a less severe problem with my idle, and other misc. weirdness. Got a new OVP for another problem and it smoothed the idle out. What that has to do with new plugs, I think that the guy that sold you the plugs didnt like the way you smiled at the counter lady he is working on getting so he went to the back and got part number 545 548 54 96KM.
the KM stands for "kill mercedes" this special plug sends an electrical gremlin through the plug wires all the way to the OVP and disables 1 small function of the relay thus your problem. Check your box for the KM. Well thats just one thought.

First things first. if the car was running good before the plug change, check your work again, also the replcement plug for that car or a 103 engine is a bosch H9DCO spark plug.

Coming in late to this one, but I find the fans to be the key in this diagnosis.

It sounds to me that you have bumped the coolant temp sensor, which is now making poor contact. This could affect the mixture and the fans. Just a guess.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

To all,

Was hot in Chicago today and the car ran fine. Aux fan seemed normal, iddle normal etc.... I will check the temp. sensor for any faulty connection. Thanks

-Larry
'92 190E Sportline