Intake Leak (can't find it, can't compensate with fuel) Options

[[Freemantle]]

I recently lost the rear main seal on my ST on the freeway, 700 miles from home. I siezed up #3 and beat the hell out of the sleeve.

So I replaced the engine. The mechanic royally screwed up my ECU harness and disconnected MAP signal on accident (I have a V-AFC wired, yes, I am using a V-AFC on purpose). I took the car home in limp mode to re-pin the harness myself.

Did it and the car ran great, stronger than when I bought it and smooth as all let out. I drove the car to work the next day without incedent. I came home for lunch and noticed that I was Idling very high (about 1200 RPMs) and the engine was making some unplesant noise, namely some raspyness in the intake note.

I tapped the trottle to make sure it wasn't stuck. No dice. The VAFC read an idle vacuum of -7.6psi. Prior to the engine swap, I was used to seeing -9.1psi (so the engine was under higher load now at idle than it ever was prior.

And the Idle climbed to 1250

and then 1300

and then I shut off the car.

When I fired the car back up 20 minutes later to go back to work, it was still idling that high and quite noisy in the front.

When I got off of work I bought a can of carb cleaner and some high-quality 22GA butt splices and male/female connectors. I redid my entire harness, and the Idle RPM still stays steady at 1300 RPM. Driveability is still supurb. I added fuel with the V-AFC. I added more fuel with the VAFC. I could get the RPMs to momentarily dip and manifold pressure to drop to -8.6PSI for a little bit, but it would regulate to the same idle speed and pressure a moment later.

I bathed the engine bay in carb cleaner. No dice. Can't find a leak althought I can **hear** the leak when driving (sounds like a supercharger spooling, if you've ever had an intake manifold leak you know what it sounds like).

Causes for concern:

A) Fuel economy is **** when at idle now.

B) The VAFC MAP sensor isn't to scale because I don't know the correct sensor type. I use 6in 6out because it gets throttle and everything else right. I was accustomed to the old motor Idling at about -9.1 PSI and pegging up exactly to 7.6psi when at WOT (I know it's wrong, just keep following me). Now I Idle at about -7.6psi and I WOT at 3.2psi. That means that I am getting worse performance @ wot than previously. I can't say that I feel difference, the ST isn't exactly a stunner, but just knowing that sucks.

So the Queston:
It has the symptoms of a leak, it sounds like a leak, it looks like a leak, but why can't I find it? And why am I pulling less vac at WOT?

Any help is mucho appreciated.

[Hanyo]

it could be 2 things, you need to adjust your idle screw, or you intake manifold gasket is leaking.

[[Freemantle]]

it could be 2 things, you need to adjust your idle screw, or you intake manifold gasket is leaking.

I'll check the idle screw, that never occoured to me because the VAFC reads 0% off the TPS. I am unsure if adjusting the idle screw will manifst itself through the TPS.

I thought it might have been the dizzy slipping because the mechanic didn't tighten it enough, but it is bolted very snugly. If the idle screw adjustment dosen't work, I have an apt to have him fix it @ 1pm tomorrow. I'll let him screw with the dizzy because he gave me a year P&L warrenty on the engine, and I don't want him to void it from some bull**** adjustment to the distributor.