Missing Engine Oil Cap, EPC/Engine Management Fault?

[Eddng]

Over the weekend with the nice weather we've had, I was giving my car a good clean and general maintenance check.

My mate offered to help by topping oil up however I wasnt sure which was the right viscosity so we left that out until I could go check the manual.

On the way home to check the manual I noticed that my car was revving itself when coming to a standstill, about a 1000rpm. A few minutes after, the engine management light came on, yet everything still appeared fine until I stopped at a roundabout.

The EPC light came on and my car went into 'limp' mode. I pulled over straight away and lifted the bonnet to find that the engine oil cap had not been replaced. I was obviously panicking and I rang my mate who told me it was probably because the engine was loosing pressure through the missing cap?

Anyway the car now always goes into 'limp' mode if the car is at a standstill, therefore I have to put revs through it to avoid the problem.

I am going to contact the dealer immediately to get a replacement cap, hopefully this will sort the problem out. Would I also need to do a oil change for the engine as I imagine there would be dust etc inside the engine now?

 

[Chino_UK]

Hmmm I'd have it flushed and a fresh filter and oil in to be safe. You don't wan't anything other than oil getting into the engine really.

 

[Slimy]

A replacement cap should solve the problem. I don't know why, but cars struggle to run with the oil cap off, I've seen it a few times for various reasons (including the 'forgetting to tighten it up' option!). I'm guessing the ECU is seeing a 'low oil pressure' issue and putting you in limp home mode?

I'd also be tempted to do an oil and filter change, chances are there's nothing in there but it won't hurt to give it a clean. you may also notice a bit of mayonnaise due to condensation forming in the engine as it cools. That should just burn off without any issues though.

 

[Eddng]

Thanks for the replies lads!

I've ordered a replacement cap.

My car is due a service/mot in a few weeks so I assume they will do the oil and filter change then?

 

[Slimy]

My car is due a service/mot in a few weeks so I assume they will do the oil and filter change then?

Well, if it isn't, it won't be much more to add it on.

 

[danny_]

i have a spare cap i woulda posted for free aswell, bit late on the post there sorry

 

[FR3000]

A replacement cap should solve the problem. I don't know why, but cars struggle to run with the oil cap off, I've seen it a few times for various reasons (including the 'forgetting to tighten it up' option!). I'm guessing the ECU is seeing a 'low oil pressure' issue and putting you in limp home mode?

I'd also be tempted to do an oil and filter change, chances are there's nothing in there but it won't hurt to give it a clean. you may also notice a bit of mayonnaise due to condensation forming in the engine as it cools. That should just burn off without any issues though.

I believe the issue with running with the cap off has something to do with the EGR system in the engine. Generally EGR valves have a particular pressure operating range and don't function correctly if certain conditions aren't met. I would guess in this case that the oil cap being off is allowing the crank case breathing system pressure to go too low which could upset the operation of the vavle.