Missfire / rough idle CE220 1994

[crooksey]

My 1994 CE220 has developed a heavy missfire and irratic tickover when warm. The missfire is mainly on decleration and the tickover can jump from 500rpm up to 1500rpm. Plugs and air flow meter have been changed. I have been told coil packs and leads can cause this. Are there any other checks to carry out before I invest in some new leads and a coil pack???.

Many Thanks
Jason Crookes

 

[kth286]

Rather than guessing, the best way is to get an experienced Merc person to read the diagnostic fault codes to start with.

Where you based - perhaps someone can recommend.

 

[crooksey]

Hull

Thanks
Jason

 

[jibcl500]

The first thing you should check is the wiring loom around the engine, have you noticed the rough running of the engine more so since we had the rain ??

Where the air flow meter is the loom that connects to it, with the engine running handle that loom from the plug running backwards and see if the engine runs better or worse. Next the battery on the left side there is a small two plug, look at the condition of that also and that plug tends to lie on the bulk head and it gets wet, over time it goes green and stops the connection.

jib

 

[crooksey]

many thanks will try then reply

 

[crooksey]

checked all connectors and all seem dry and uncorroded.
checked for spark along leads when idle problem occured all seem to be working. no apparent air leaks. puzzled??

Regards
Jason

 

[crooksey]

the car can tickover happily for 5-10 minutes then all of a sudden will start loering and raising the tickover irrtically. Then it will settle again??

 

[television]

The OVP relay can give troubles like yours, you can check it from the N3 ECU and measure across pins 1 and 3 where there should be 12 volt

 

[crooksey]

Thanks Malcolm
Where is the n3 ecu? and the relay? situated

 

[television]

114 in the link for the ECU

http://www.detali.ru/cat/oem_mb2.as...GM=717.413&CT=F&cat=15T&SID=54&SGR=075&SGN=04

The OVP relay is 119 in the link or by the battery

http://www.detali.ru/cat/oem_mb2.as...GM=717.413&CT=F&cat=15T&SID=54&SGR=040&SGN=03

 

[crooksey]

do you test it with the ignition on or off

 

[roofless]

also check the throttle returns to rest on the stop & makes contact with the micro switch on the throttle body