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.

[95celgt]

i dont know much about the st yet, because I just got one like 2 months ago, but mine also idles at 1300RPM after the engine was swapped, and the only code it is throwing is a bad EGR, dunno if thats the problem. My "R" port on the throttle body has no where to connect to on the EGR system so im in a bind, cause after reasearching the ST, it seems it has a 96+ year 7afe than its original obd I 7a......

[shin]

you installed a afc, so maybe you're dumping alot of fuel into the engine?

[[Freemantle]]

you installed a afc, so maybe you're dumping alot of fuel into the engine?

0 setting across the board, same setting from the old engine as well.

As far as OBDI and OBDII, in my experience with Hondas, they run completely different ECU harnesses and ECUs. I'll go pop he hood and check the block code anyway though, good thinking.

[nik]

' date='Dec 19, 2005 - 10:43 AM' post='368937']

you installed a afc, so maybe you're dumping alot of fuel into the engine?

0 setting across the board, same setting from the old engine as well.

As far as OBDI and OBDII, in my experience with Hondas, they run completely different ECU harnesses and ECUs. I'll go pop he hood and check the block code anyway though, good thinking.

94-95 are OBD1 and you can loosen the bolts to change the timing
96-97 are OBD2 so the you have to change the timing through the ecu

[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.

[Kwanza26]

' date='Dec 20, 2005 - 2:17 AM' post='369123']
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.

You'll be leaking oil if the dizzy is loose...

Maybe it's the timing. Carb cleaner can find just about any intake leak under the hood.

[[Freemantle]]

' date='Dec 18, 2005 - 10:27 PM' post='368745']
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).

The only place where I may have not gotten carb cleaner was underneath the intake manifold. As soon as it stops raining, I'll pull the car into the garage and check the idle adjustment screw and put my interior back together.

[[Freemantle]]

Idle Air control was fine. Took it to the mechanic today. The noise I've been hearing that sounds like a whine is my water pump (which is going bad). He's replacing it, but he can't do it until next week Wednesday . The high rev is due to the bearings failing and the lack of proper load on the crank pulley. Thanks for all the suggestions.

[95celgt]

what bearings are failing? what do you mean on the proper load part?

[Kwanza26]

Hehehehe... funny.

[[Freemantle]]

what bearings are failing? what do you mean on the proper load part?

The waterpump failing changed the idle state to a lower load. This brought up engine rpms in a very "boost-creep" like fashion.

So I have the new waterpump in, but it is loud! I can't hear it with the stereo on, but it definately whines. Any way around that?

[Blakout16]

when i put in my new alternator from toyota that thing whined really loud too... nice tho but still...

[Hanyo]

the whines can be cause by the belts being too tight.

check your belts.