Weird engine issues starting from cold....

[DuncanPoundcake]

ML W164 320 CDI - I have a curious problem.

On Sunday, I started the engine from cold and the idle was hunting up and down. It had no power when driving and kangarooed very slowly down the road.
I managed to drive it round the block and it eventually stopped playing up and worked fine.

On Monday, I started the engine from cold, auto choke came on, then dropped away and the engine died. Started again, choke came on and stayed on at 900 rpm but it was still un-drivable, as above. I said on the drive and let it warm up for 10 minutes and it was able to drive OK.

Yesterday. my wife started engine from cold. Revs held at 900 rpm, let it warm up for 5 minutes drove away, had a couple of kangaroos but OK after that.
This morning I let it warm up until the choke dropped away and it drove OK.

The injectors have just been replaced and the fuel system has recently been worked on, new fuel filter, new air filters and the pressure is good all the way through.

I fitted a new Y-Pipe in the summer, so the MAF sensors shouldn't be an issue (??)

On the face of it, seems to be temperature related, could this be an EGR problem, sticking closed until, with enough heat, it opens up?

 

[PR1]

I’m slightly confused when you say auto choke? The cdi is diesel so no form of choke. Are there any warning lights or messages? Including abs or esp? Is the glow plug light working normally, as in going off and staying off? I doubt that a sticking egr valve would cause it, and would most likely throw an engine management light. Is it possible one of the replacement injectors is sticking? Or did they work ok for a while before this problem.

 

[Dodipops]

If I had to guess then I’d say a back pressure sensor or turbo actuator from your description but that’s a guess.

Need to get it scanned and tested.

If no fault codes you’ll have to look through the data, I’d be looking at coolant temp sensor in case it’s reading wrong??

 

[mersum1es]

That sounds just like injector leaking, even they are new (or refurb?), do a leak test on next cold morning. Yep, back pressure does the same but it is not usually temp related. Sticky egr, perhaps... but again it would probably play up also at warm.