XBLADE

Car: S5 TII engine streetport.Haltech RE ECU. 1000cc secondaries. FD pump. FMIC. KOYO. Full RB exhaust. Over boost in ecu set at 7 psi still since I was breaking in motor and have been driving it casual for the most part.

Last job I did on it was LIM and UIM manifold gaskets, fixed all boost leaks and the car idled and pulled strong in boost again.

A couple days ago I was getting up to speed @5 psi and it felt like I hit the fuel cut from the overboost function. The next pull was fine. Well its gotten worse of the past couple times I drove it.

Now the car wont make boost. It just feels like fuel cut as soon as I hit 0/atmospheric pressure. Feels like the fuel kicks back in as soon as I let off of the gas..

Checked all IC piping and couplers. Turbo has no oil in the inlet and there is no shaft play in any direction. I can open wastegate by hand.

The car drives 100% fine out of boost. Idles like normal. -19vac @ 1k idle. You can hear the turbo spinning faster as you get near boost (no funny noises) and it just cuts at 0. Tach still shows RPM so I don't think it stalls. As soon as I let off the gas its driving out of boost fine again..

professionalpyroman

Check boost leak. You might have had a vac line pop off or get a hole in it. Best place to start looking for this problem is the intake lines in the stream after the turbo but before the throttle body. The intake on a turbo car usually has little vacuum between the turbo and the throttle valves, so it usually runs well up to positive pressure. When there is a boost leak there, the mass air sensor says there's a bunch of air coming in, but its escaping somewhere before it makes it to the engine. Check for vacuum leaks too while you're at it

XBLADE

All emissions are deleted. All my vac caps are on tight and I only got 1 vac line (T'ed) for map sensor and boost gauge. I've had IC pipes come off and vacuum lines come off before and this is different. The engine hits like a cut when it gets to 0. If I had a leak it'd still drive normal just not make any/as much boost or have some noticeable idle problem. When I had the LIM vac leak (was a loud as fuh hissssssss) it would still go into boost but spudder at 3-4 psi.

Today I was able to randomly slow roll into some boost in 4-5th gear and got up to 5psi, then next time I tried it cut at 0 even when only trying to make 1-2psi this pull.

Maybe a trailing coil problem or plug wires? I did put new plugs recently and I got these wires with my JDM engine so who knows on their condition.

professionalpyroman

Ok then, is your wastegate stuck open? Did leave a rag in one of the intake runners?

Coil could be misbehaving, but you'd have to check it to be sure. Could have a TPS sensor goofy, oh the possibilities. FSM has a problem chart, with a priority of the likely suspects.

I don't know if you can pull codes off a Haltech, I haven't bought one yet. If you can, check those.

Rob XX 7

iTrader: (8)

before this goes any further- you said you are breaking in the motor, is this a rebuild with the same set up you had before? are you driving untuned?
it doesnt take much to blow an untuned engine once you go into boost. not even "just the tip" is ok

XBLADE

It's almost 2k miles now and never had a problem. Engine has been consistent and still is. Still runs good and starts as normal just as it always did. Just cuts at 0 on boost gauge till I let off the gas then its fine again. Doesn't seem to be lacking any power.

XBLADE

Thanks for the feed back guys, it's always appreciated. I finally got chance to mess with the car. I was inclined to believe it was an ignition problem so I swapped some T coil wires off of another 7 I have. The car fired up and drove into boost no problem. I usually drive the car 3k and under out of boost so it coulda been getting worse over time and I just didn't notice.
All in all, back in action