Odd performance issues and cut out plus error code

[LeedsMike]

Very strange thing happened on a drive today. Was returning from a car show when on the way the car was running the best it has ever done.

On the return home, when I started the car the idle seemed a little higher than usual and when I was accelerating quite hard to 60mph, I got a backfire, then a cut out, then the engine warning light, then everything cleared and returned to normal....

Anyway, a little while later the car seemed a little down on performance and was quite warm. The turbo gauge all of a sudden stopped working but i think I was still getting boost allbeit not as much as usual...

Then, left the car to cool and attached Elanscan and went for a drive around the block - boost gauge working and performance back to normal - but the Elanscan did register a 4000 code and overboost "on" and it stays like that. Is that normal?

Worth pointing out, I have a mountain chip (Everest 4.5) and a sports exhaust but have never suffered from creep...

Any ideas?? Thanks is advance!

[MPx]

Sadly no ideas

...but it does sound very similar to the issue I'm experiencing at the moment - noted in the last few posts of the Castle Combe thread. Differences include: my turbo guage stays working; overboost was once and momentary and didn't coincide with the backfire; I have a V5 - issue is similar in Everest and Kilimanjaro; wastegate has been ported to 21mm - no boost creep. Will watch with interest how yours is solved, best of luck.

[LeedsMike]

Just had a quick read now.

I think I need to set some time aside for some recorded test runs. Luckily I have a 1 mile straight stretch at national speed limit nearby so I can at least try different engine loads/gears/throttle position/boost profiles….

Reading the thread you mentioned and others, it’s the combination of issues that led to the overboost and then the next 30 mins that followed (that then cleared up) which is odd.

The car was odd from the moment I started it up (idle higher than usual).

Does anyone know if the standard écu or Mountain chip upgrade would run a different profile if overboost was in memory? I did read somewhere that the écu has the ability to learn engine condition and adjust parameters accordingly. Perhaps something happened around startup….?

[LeedsMike]

So a little more.....I ran a few tests this evening and managed to recreate the problem:

Allowed coolant temperature to get to 3/4 on the gauge just before the fans kick in (this was to simulate the heavy traffic I was stuck in and to reproduce the coolant temp at the time). I did this by sitting still with a warm engine running for 5 mins. Temp was 111 degrees c.

I then ran at full throttle in 3rd gear and the boost was limited to around 0.25 - is this by design?

I then drove at around 20mph for a while to let the car cool down to 1/4 and tried the run again - this time the boost surged to 1 bar and overboost limits kicked in with engine light coming on. This was confirmed on Elanscan. I then repeated but the car returned to nearly normal performance.

The temp was 91 degrees when the fault was detected.

Any thoughts on this that could help ID the issue?

[LeedsMike]

So, another longer run today reproduced the fault but with a completely different build up. Suspect it is now something to do with a stuck waste gate based on reading other threads.

This could also explain the strange boost behaviour that is not in line with the Mountain programming….

What ElanScan plot would be best to prove this theory before I start trying “the wiggle”?

[MPx]

Again I can't help with the Elanscan stuff....but I would say its worth doing the wastegate wiggle regardless as its very easy (even for me!) and eliminates a potential issue. You simply need to get the shiny actuator rod right at the front of the engine bay, in a pair of mole grips and see if it moves. The word "wiggle" is unhelpful I found as it implies an ease of movement that isn't there. It takes quite some force to move the bar so there will be no wiggle going on. But basically if you can move it a bit left and it springs back right, then the wastegate isn't stuck.

There's other stuff that then comes into play. Pinky kindly replaced the short length (say 70mm ish) of pipe going into the actuator housing on my car, as if that is split/holed/leaking then its never going to be able to force the wastegate open....and so on, you can trace the pipework back. There was nothing wrong with mine it turned out. You can also test using a high pressure bike pump if you can get a reasonable seal on the bit of hose you disconnect.

Anyway, on my car my suspicions have moved away from an overboost issue to a fuelling issue as I'm getting a definite backfire before the CEL comes on and the odd pop and bang at other times, but I'm not really sure how I'm going to proceed from here as I appear to need a track session to test ...