Engine "cycling"

[Kiwibins]

My 1995 E320 Coupe tends to idle slightly poorly when sitting a lights. It "cyles" slowly and randomly from 400 - 1000 revs. What could cause this? I know the car is due for a service - will this cure the lil issue?

Greg

 

[Stevie A]

Erratic idle is usually caused by the OVP relay being faulty, but is usually accompanied by symptoms like harder starts, occasional stalls and erratic ABS light.

 

[television]

Yes OVP faulty, not a good year, either solder all joints on the PCB or replace.

Malcolm

 

[kth286]

I think the OVP was sorted previous to your model, so unlikely.

It could be a vacuum hose letting in air and causing cycling as the ECU tries to compensate and adjust.

You should get the codes read by a technician that does understand and has experience of your car.

Otherwise a failed lambda probe in the exhaust - perhaps.

 

[Myros]

Not sure about OVP sorting in 95

my late 94 C280 had a faulty one. That's what brought me here all those years ago.

 

[television]

my late 94 C280 had a faulty one. That's what brought me here all those years ago.

Myros is right,some made in the eastern block,others Irish,ones OK the other is bad, cant think which are the bad ones, I will take a look next time.

Malcolm

 

[Kiwibins]

Just the idling....

The only fault is the idling being lumpy with no acceleration. No other symptoms. So still OVP or something else?

Greg

 

[Myros]

The symptoms on mine were

the occasional non-start, which could last 5 mins or 3 hours. It did it to me in a french supermarket petrol station once, and we had to go shopping so I didn't flatten the battery out of frustration. A lot of wine later, it started first time. It would be okay again until the next time it did it. Final straw was a 3 hour session trying to get to work one day, and the increasing frequency of attacks.

It could any of a whole bunch of other stuff as well Greg. Maybe Malcolm has some ideas. An OVP will cost you £50 to find out.