BFMK2 issue just started: Full boost loses power and sounds kind of like rev limit

[traffic]

My car has been tuned about 18 months ago, I've got the X4, full exhaust, front mount, running max 14psi.

 

Been running perfectly until a couple of weeks ago. When I accelerate hard it takes off until it seems to be about full boost and then it loses power and sounds like it's missing/hitting rev limiter or something. If I back off slightly so it's just under full boost, all good car accelerates fast like normal, and perfectly smooth.

 

I couldn't see anything obvious with a vacuum hose come off or anything. Plugs are like new, and I just got it serviced.

 

Any ideas would be appreciated. Maybe there's a way I can log some useful info or something on the X4, but no errors come up etc.

[k31th]

coils, at a guess... or spark plug gap is too big (or a combination of both).

[Puffwagon]

It does sound like a spark issue. 

 

My car did the same thing when I turned it up. 

 

If the plugs are 18 months old then they could be due for a swap depending on the distance you've traveled. 

 

I run a 0.68 gap myself. 

 

My approach would be to first make sure there are no overboost cuts happening, check every gap, not just one or two and then swap the plugs. 

 

If that doesn't rectify the issue, I'd look to coils.

 

It's somewhere to start mate. 

[BAXRTUTE]

Could it be valve springs? 

[Puffwagon]

Not likely, as it happened suddenly.

 

That would be a gradual occurrence that starts in the upper rpm band and slowly moves down as they go soft.

[k31th]

and soft valve springs give symptoms of rough idle straight after giving it a flogging.

[traffic]

Thanks for the quick replies! I'll pull the plugs out on the weekend and check them. Is there anything I should look for/test on the coil packs to know which one(s) are the culprits if any?

[Puffwagon]

Grey marks on the coil packs will indicate that there has been a current leakage.

 

Also there could be swelling and cracking on the winding (top) part of the coil.

[ROB83R]

Any moisture near or on them renders them useless also. 

[discostig]

Coils and or plugs as a first point of troubleshooting, not toooooo costly.

 

My last set of Motorcraft plugs and VDO coils were in the car for about 150,000km (oops).  Car doesn't seem to go much better with the new ones I just put in hahaha!  320rwkw / 15 PSI tune but spikes to 20 on gear change in the ZF.  There wasn't a problem before aside from a slightly rough idle at times (which is still there) but I knew it was way overdue so did it anyway.

Edited 22/11/16 10:31 AM by -Stever-