G*d D**n s*n of a b***h!
just did some messing around and took it for another drive, i still have the same bloody problem, so now i know it isn't grounds... i've searched and have never seen anything like it.

SYMPTOMS:
1. turn car on from cold - all systems normal
2. let it warm up, revs drop to 800rpm and vaccum to -0.5BAR flat - no bounce or irregularity.
3. take it for a drive - boosts to 7psi perfectly and pulls strong (no pills or MBC)
4. do flat foot run - boosts to 7-6-7 at transition pulls strong all the way.
5. another boost run - fine
6. another boost run - reads 7-6-7 but my butt-dyno says it has bugger all power
7. return to idle - vacuum now reads -0.3BAR and is lumpy! loud exhaust note and popping in cat
8. shut down, reset ECU - harder to start and stays lumpy and crap
9. let cool completely
10. (see #1.)

does anybody have any idea why it is doing this? there are no heat problems, no smoke issues, no ground problems, no starting problems.

the only thing i can think of is a stickey seal?
maybe some ATF would sort that out?!

 

It doesn't sound like any kind of boost issue. To me, boost is about producing pressure in the manifold. Whether you have power from that boost makes it either a fuel, ignition, or engine issue.

I would take it to someone with a wideband O2 gauge and see if something funny happens to your AFRs when it gets goofy. How do the plugs look?

Dave

 

plugs look fine, pulled them and cleaned them today in the hunt.
based on the fact it starts and runs beautifully after cold until it gets some heat in it, and a 'ear compression test' the engine side of things is fine, and i have 3mm RA seals in there

which leaves fuel and ignition - i might pull the plugs and test them for spark against the block to see if maybe it is leads... could be coils.

doing my searches, the fact that it doesn't flood on start makes it unlikely to be leaking injectors... kinda makes me think i have an ignition problem - how would that only show up after a couple of boost runs?!

 

Also check your Intake Air Thermosensor - if it's reading too high, the car will lose power.

Dave

 

If it's the AIT it should throw a CEL code. 11 I believe. Could be 17? One is the AIT and the other is the o2 wire.

 

I don't know how common this is, but if the resistance is reading somewhat off it won't set a code but it will indicate an abnormally high temperature. So if there are no codes it might be worth testing the IAT the next time the manifold is off.

Dave

 

Could also be the harness going to the coils or the coils themselves - when they get heat soaked, you have ignition problems, and when they cool it's fine again.

I agree with Dave - I think this sounds like less of a turbo control issue than a fuel or ignition issue.

Dale

 

how would i solve the heat soaking? and/or the AIT?

 

oh, you guys are GOOOOOOOD.
my ignition coil harness had a loose wire in the plug... pushed it back in - idle fixed itself and vacuum went back to normal INSTANTLY.

my guess. under boost the engine moving around a little pulls on that wire... need to make a permanent fix.