05 R53 loss of power
 

Entering the ramp to the Turnpike today I decided for a nice uphill accelleration to increase some cool air in the face and for a quick blast. Unfortunately as I got off it and idled back down to cruisling speed i felt instant problem.

Engine felt way off, very little power and boost guage could barely go beyond vacuum. No lights came on, oils fine, coil pack???

Pulled over and took a look and found nothing obvious.... Was able to drive it home. Pulleys looked fine but skips and sputters.... thinking heat and coil pack or can there be something in throttlebody or fuel filter?

Any ideas out there

Thanks
Braxton

You're in what's known as "limp mode". Surprised that you didn't throw a CEL. Check all your possibilities for an unmetered air leak like IC boots, etc. If not, my guess: Possibly bad MAP sensor.

Check your belt tensioner and idler pulley. The belt should not skip and sputter. If the belts is slipping you will get exactly what your problem sounds like.

Check your bypass valve. Spring could have broke = not closing = no boost. This is a common problem. When the motor is off, find the little arm coming out of the bypass valve. Make sure that when you open it you feel spring tension....and when you release it make sure it shuts with some force. If it's "limp" feeling and doesn't snap shut.....the spring is broke.

Update
 

Thanks all for your help. Unfortunately my #3 cylinder valve i guess decided to fail. mechanic just took a pic of it and tested cylinder and no compression Valve picturecshows it pitted and some pieces broke off
Hes gonna check out lower end to see if there is any more internal damage


Its an 05 minis with a jan rmw tune. Am i understanding this correctly. Best case is a new head ? Worst case a new or rebuilt engine

Good oportunity to do a BVH if performance is an interest, will last as long or longer than a stock head and IMO, far better materials used.

(BUT, you should check with Jan or plan on getting a new tune asap if you do this, if you don't the old tune should be fine unless your mechanic thinks the problem wasn't stricktly a part failure.)

Good Luck

I don't see why your mechanic just couldn't install a new valve and valve seat....no need for a complete new cylinder head. Most machine shops should be able to take your head and repair that one valve pretty cheap......well, at least cheaper than a brand new cylinder head.