So my friend took my car out for a test drive yesterday, when he came back, the car was barely idling at around 500rpm and if i would cruise to a stop it almost die out. Vacuum reads extremely low 5 kpa. However it is driveable, during partial throttle it feels like crap and isnt smooth. If I WOT it feels normal, until about 5000RPM, then it just hesitates to go above that. I currently do not have a compression tester, but I did turn it over by hand and I get 3 puffs when I turn the motor over. Another weird thing that happens is that the BOV does blow off all the way and creates some turbo flutter, which is probably caused by the low amount of vacuum.

S4 T2 block
720cc Injectors (all four)
Haltech E6X
All GM sensors (TPS, MAP, IAC, Coolant Temp)

 

sounds like the same thing that happened to my engine. Im not sure what 5kpa translates to in lbs of vaccum.

But I was curising home and when i was getting off the freeway the car shut off on me. It had a really hard time starting I had to cut the fuel to get it to run and even then i had to hold the thorttle to keep it alive. Drove fin though

I ended up having 10lbs of vaccum and it barely idled after i bumped the timing. Turns out it was low compression on the front rotor. I didn't blow a seal yet but one of the seals was starting to give out. confirmed by a compression test.

One time before i also thought I blew my motor drifting, turns out I just ripped a cheap autozone coupler. so check anything visual first and compression test before you start tearing stuff apart.

So go ahead and do a compression test before taking it any further. I mean it could be that it blew off some vaccum lines. Ripped coupler, bad seal around intake manifold maybe.

 

5 kPa = 1.6 inHg = 0.8 psi
(http://www.wrh.noaa.gov/slc/projects...Conversion.pdf)

Vacuum gauges usually read in inches Hg, and around 20 inHg is ideal. 1.6 is extremely low, and it doesn't sound like a huge vac leak. That would likely keep the motor from idling at all or even starting. I had a vac leak between the UIM and LIM once that brought my vacuum at idle down to 10-15 inHg, and the motor barely started/ran.

Compression test time.

 

Your friend doesn't by any chance have a honda do they? If so, thats your mistake right there. Their a curse

 

no he did, i was working on his 7 when he was test driving it, im pretty sure its blown though, time to learn how to rebuild a rotary

 

check the vacuum line going to the BOV and any other vacuum lines, my vacuum hose fell off my bov once and ran like crap and wouldn't blow off, once it was reconnected it ran fine.