KV6 lumpy running
 

Hi

I have a 2004 ZT with the 2.5 KV6 that's done around 84,000 miles. Not had it long but have looked after it since purchase.

I suffer regular but intermittent lumpy running when the engine seems to miss and progress from quite low speeds is hesitant. This is now usually accompanied by the Check Engine light flashing for the time the engine is struggling. I have had the light on solid as well but currently it's off and (as I say) just flashes and then goes away.

The rest of the time the car goes well.

Events: I had a flood in the car from a blocked plenum chamber weeks ago and learnt the painful and overdue lesson about rodding the drain hole.

I don't know if the ECU is in poor shape from water ingress/age? Or whether the ECU could even be a factor (I don't mind sending the ECU off to the ECU Doctor to know the worst). I suspect the flood I suffered wasn't the first time the plenum chamber has become blocked prior to my ownership.

Does anyone have a suggestion what the culprit might be or how to go about establishing the cause?

Many thanks!

The ECU on MGR petrol engines is watertight sealed - its the diesel ECU that is at risk of drowning as they are unsealed. Am not KV 6 man but a regular issue that can crop up is malfunctioning VIS motors/valves - might be worth running an OBD on the car to see what fault codes. In my Turbo first port of call for lumpy running would be the ignition coils and spark plugs - a failing coil will get cause a flashing MIL.

Just working on my newly purchased 04 V6 and despite the garage owner telling me the car had been recently serviced a few suspicious items led me to have a look at (first) the rear plugs (doing the cam cover gauze filters too). Anyway there is no way those “glued” in plugs are recent, the gap is about 1.4, brown deposits on the ceramics and original MG / Rover plugs. Might not be suspicious in UK but a garage in Sweden?

So give the car a good service yourself and you’ll know it’s been done properly, plus get yourself a code reader (Toaf is free) it could save you lots of guessing / time.

Regards

Thanks both.
I'd appreciate more feedback from anyone with similar experiences of course but will plug in a code reader.

This is going to sound silly but VIS motors/valves are super complicated/costly or something less than that?

The coils sound like a possibility. I had the plugs changed with the last service in October so they ought to be fine...

Sent from my G8341 using Tapatalk

Forum member Stocktake does a reconditioning (better than new) service for the VIS motors, at what I consider to be a very reasonable price. I supply local owners with replacements so quite a few have passed through my hands.

A code reader will pick up things like coils and sometimes even VIS motors, Toaf will tell you even more and let you activate the VIS motors, fan, etc.

Moral of my last post was you can't trust garages. The rear spark plugs are a job for Houdini and unless you do things yourself, or are 100% confident of the garage, you can never be sure.

I had a check engine light on my V6 but it was constant, low fuel pressure now sorted.

Regards

Hi - assuming you are in Wimborne in Dorset -there is a T4 guru in Portsmouth - CB750Chris he is a trader on this site - drop him a PM - T4 is great piece of kit and will soon tell you whats happening.

Problems with your VIS motors are more likely to manifest themselves in general sluggishness. A duff balance motor will make it generally sleepy and a dead power motor will mean you don't get that kick of acceleration at 3200 revs.

Your warning light could be related to unburned fuel in the exhaust as a result of a knackered ignition coil. The symptoms come and go as it goes into its death throes. Being an 04 vehicle yours will take the "short" type which are reasonably easy to come by.

I too think it more likely to be a duff coil pack. Had similar on a previous V6. Get an odb2 connector and app to try to determine the fault code or let a T4 guru ply their magic

Stubs