2008 XKR (4.2 Supercharged)

Am I incorrect in assuming the MAP sensor should be reading boost, at least off idle or at cruise?

Was streaming live from icarsoft reader and only saw vacuum ~14 @ idle to 42 give or take going up freeway ramp.

No DTCs or anything. Doesn't run rough or idle abnormally. Is there some sort of bypass valve that may have failed open?

 

There will always be a vacuum in the intake duct upstream of the supercharger.

Richard

 

Yeah, but Manifold Absolute Pressure is at the manifold, not above the blower.
My Torque App shows PSI whenever I mash the skinny. In/Hg at cruise or idle.

 

This was my train of thought. It should see some positive pressure. Unless I'm missing something, I'm not seeing any.

 

Have you hooked up any other diagnostic tool? I've never used an iCarsoft, so no opinion there.
Maybe bite the bullet and buy a bluetooth OBD2 adapter for like $10? Then you have the option to use several different apps to see which one meets your needs. I have Torque Pro and thanks to Sean, I have any part of the vast possibilities of Torque whenever I choose:

 

Haven't tried any other, but may look into that, if nothing else than to verify accuracy (or inaccuracies) of the icarsoft scanner.

 

There is a bypass valve that sits on the intake plenum in front of the throttle body. It opens to dump from the intercooler back into the intake for the supercharger.

The valve is normally spring loaded closed and opens when vacuum is generated at closed or partial throttle. i actuated mine with a hand held vacuum pump to verify.

I think it is unlikely to be your problem.

 

Maybe something to check though. It seems I'm not making any boost, but car is not running poorly nor are there DTCs. I can still hear supercharger wine, but still reading vacuum at MAP sensor. Butt dyno feels noticably off too.

 

Did the belt come off?

 

Lol no belt is still on. Can even hear supercharger whine when I get on it.

 

Found this. Maybe not cause, but def not helping.

 

Hard to see what you are pointing at - a larger resolution picture would help.

 

Sorry hard to get the phone down in there, the throttle body boot to air hat is split completely.

 

That boot is not available separately unfortunately, it comes with the aluminum tee fro around $1000. Other members have sourced a replacement boot elsewhere. I'd take it to a local auto parts store and see if they can find something similar.

 

Ah, now I see it. Some members have had luck with silicone plumbing fittings from Home Depot. Search this forum, should be able to find their stories.

 

Thanks all. Will browse other stories and see if I can't find a substitute. Definitely not keen on paying 1k for the whole assembly when just the boot is bad lol
And still need to find out why I am apparently not making boost. Will replace boot first then continue on. Will update when I find something.

Weirdly, despite the boot being split, no MIL. I figured the MAFSs would not like that.

 

When I had my valley hoses changed recently they managed to kink the throttle body gasket causing a vacuum leak.. Very rough idle at cold start up, when warmed up the car ran perfectly. At idle the long and short term fuel trims were very high. Have you checked them at idle?

I was not getting any DTC's with the vacuum leak.

 

May be check the map sensor and wiring, also check with another reader as icarsoft is good but I found mine gives some odd readings, if you were producing no boost the car would be very slow, the valve timing and compression is set for boosted engine and in my experience once you lose boost they are very slow.

 

maf sensor has to operate over a big range at lots of different speeds and loads, often they won’t throw an error code unless there is an electrical issue ie open or short circuit.

 

I checked them with icarsoft reader, I dont remember exactly the numbers, but at idle three were near zero, and bank 2 long term was around 5 or 6% or so. I'd have to look again to be certain on that. May do this afternoon.

Car doesn't run rough. No hard start, no sound or indication of a vac leak. Butt dyno telling me not as responsive. Would need to get to the track or use my Drag app thingy for some 0-60 to get numbers on any change (loss) in performance.

Was wondering if possible the supercharger internals just got deleted or ?