odd revving C5 mark 2 138 bhp auto diesel

[kevino]

Hi guys, not been on here in a while. I've got a C5 estate, mark 2, diesel, 138 BHP, auto. The issue is if I gently accelerate the revs go up and down while i accelerate, approximately 300 revs difference., this happens through all gear changes, but if i put my foot down it accelerates as normal. Problem is i like to drive gently but this fault is starting to cost me a lot more fuel as i am having to accelerate quicker. Does anyone know what this fault could be? Many thanks in advance, Kev.

[moizeau]

First and easiest test is to unplug the MAF and see if the problem goes away. It will throw the MIL on.

[kevino]

I'll give that a try tomorrow. I've got a code reader so I can reset the fault after trying it.

[dulenator]

I have the same problem.

The diagnostic says there is some kind of issue with the EGR valve (can't remember the exact error and don't have access to the diagnostic tool at the moment).
In my case, this happens intermittently and usually when the tank is below the half mark.
I can also hear some relay clicking on the left side of the car in the interior fusebox when the stutter is about to happen.

It could be that the EGR is causing this issue because I think the valve should be open on low and closed at full load.
Maybe it gets stuck in the closed position, tries to open, and confuses the ECU.

I will confirm everything when I change the EGR valve. I have it in my trunk, but what I don't have is time.

[Rp0thejester]

I would ask, have you tried an EGR Cleaner? It may help to clean the EGR but also help possibly rule out an EGR problem if it persists. Could even be a faulty MAF sensor.

[kevino]

I have the same problem.

The diagnostic says there is some kind of issue with the EGR valve (can't remember the exact error and don't have access to the diagnostic tool at the moment).
In my case, this happens intermittently and usually when the tank is below the half mark.
I can also hear some relay clicking on the left side of the car in the interior fusebox when the stutter is about to happen.

It could be that the EGR is causing this issue because I think the valve should be open on low and closed at full load.
Maybe it gets stuck in the closed position, tries to open, and confuses the ECU.

I will confirm everything when I change the EGR valve. I have it in my trunk, but what I don't have is time.

I must admit it does it less if I put redex in the tank. EGR valve was replaced last year after it completely failed. Replaced with a new unit.

[dulenator]

I would ask, have you tried an EGR Cleaner? It may help to clean the EGR but also help possibly rule out an EGR problem if it persists. Could even be a faulty MAF sensor.

I will change the EGR valve these days and then see if it will change anything.
There is a "but" because I poured more expensive fuel with additives, and now I'm almost on an empty tank with almost no issues. There was one or two judders, and that's it!
It seems it is somehow fuel-related since @kevino had the same result with the fuel additive.

I'll try one more tank with "better" fuel and if everything is ok, then I'll try the cheaper variant.