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240 My 93 245+T and the phantom vac leak.

EivlEvo

Active member
Joined
Sep 11, 2012
So friends. 93 245+T

I have completed my 19T turbo upgrade, and the car is back together. I have my megasquirt waiting in the wings, but for now I'm still on the TLAO 2.4 chips.

If I run my HKS SSQV, the car will stall if I rev it while stationary. With the CBV installed, it doesn't do this BUT...

If I have a relatively quick transition from boost to braking... it'll almost always stalls (it fights hard though). I actually had Mike (TLAO) test the HKS setup on HIS car and it worked perfectly fine. So it is a sealed unit. For good measure I tried with upgraded o-rings and reported no change.

Mods.
93 245 +T. 19T. 3" AMM with 577cc/min injectors. Ebay IC. IPD turbo cam. Car was auto and is now T5. 3" exhaust with cat.

I have smoke tested and found nothing. I have sent propane around with no changes. I've sprayed starting fluid with no changes. I have boost leak tested (WITH soapy water) and found my oil dipstick tube o-ring needs to be sorted (this weekend). I have swapped AMM's around between known good ones. Same with IACV, TPS and O2's. My brake booster and my check valve "pass the tests" and there is no change in the stalling issue if I isolate them (with the HKS I can rev it while stationary and stall it).

I had the intake manifold off to clean the PCV system (which was remarkably clean tbh) so it has a new IM gasket and a new TB gasket with no changes.

Compression is GREAT and even across the board. Vac is generally around 22" at idle.

There's no change between the 15G and the 19T (for this problem) and this also entailed an entirely new downpipe.

Otherwise car drives great, boosts fine and is reporting fine mixtures.

I'm lost here guys... what COULD I be missing?
 
Mine did roughly the same.

Ran great when it was still NA. Immediately when I did the +T it would stall when going from boost to idle (with clutch in, stop go traffic etc).

Found that 'base idle' was set way too low. No you can not adjust idle rpm. But the throttle plate needs a certain opening at idle. Adjusted the set screw for the throttle stop, adjusted tps, no stall again.
I set idle with hose tot iac closed off to 500 rpm with a slightly warm engine.

Maybe this helps!
 
Sometimes it is simple mechanical adjustments like above that will fix things. I've had to fix that exact kind of thing on 240 turbos when people messed with the throttle plate adjustment.
 
If it adds to the flair, I have indeed adjusted the idle based on the book spec for LH 2.4. At least it seems as though I have. I'll fiddle again I suppose It's worth investigating further at least...
 
Alright so...

Today I yanked my throttle body because the LAST time I had it out, I noticed (via BLT) that the shaft seal was leaking. I had replaced that seal in the interim with some orings that seemed fine. I wanted to replace it with the correct seal (which is supposedly a valve stem seal). Did the swap (along with a new TB gasket, I replaced the green oring underneath the breather box because there was a boost leak there as well, and also replaced my oil dipstick tube to block oring.

This hasn't worked. I'm getting a massive air leak and I can't find it at all (ran out of light and blood for the mosquitoes). I suspect it's from the TB shaft seal. I tried going back to the old seal, no dice. I tried a combination of the two, no dice.

Questions:
1. WTH? How can/should I seal this?
1a. I suspect that my issue might actually be that that TB shaft is twisted because my TPS is adjusted to absolute MAX and I can BARELY get it to click with the plate (isolated) closed all the way.

2. Can I just swap my TB from my 2.2 car to my 2.4 car? Yes I know it has the idle adjust screw and 2.4 handles idle but... is it something I could simply back off?

I need help tbricks.
 
It is also possible the throttle shaft is worn creating a leak unto itself that no amount of o ring replacement will help. SU carbs and the old Solex carbs on Beetles are very known to do this kind of thing and it can probably happen on a throttle body as well.

Yes, the throttle bodies can be switched as far as I know. It's basically just the thrumbscrew for the base idle which you are already familiar with. You disable the idle control and use the thumbscrew to give youi base idle.

BTW what is your idle? Turbos should have a slightly higher idle around 900 rpms but the n/a idle is 750 rpms.
 
I think my idle has always been around 750 (based on the tach)... def not 900, but I suspect getting it to 900 would solve some of the challenges tbh.

How does one disable the ECU idle control? Wouldn't I disable the screw instead?
 
Yes, a 900 rpm idle is what you want with a turbo engine. I remember on 240 turbos there is a white/blue wire you ground. But I don't remember what you do off hand with LH2.4. A bentley or haynes manual should have the procedure or if you can find the online green books with that section.

It maybe that you clamp off the idle bypass hose and see what your idle is. Then adjust the throttle plate so it's got the base idle of about 750 and then with a turbo ecu and unclamping the bypass hose it should regulate at the 900 rpms. This is probably a setting you could talk to the person who supplied the chips for your ecu about if that isn't happening. You most definitely should have a higher idle than 750 on a turbo engine.
 
For LH 2.4 I always just adjusted the screw on the TB for the throttle plate adjustment. Very quick and easy.

There is no need to disable the iac motor. Then again if you want to just unplug it and cap off the hoses. My 12 sec 744 ran without an iac valve for years and I just used the adjustment of the throttle plate to set the idle and it had zero issues.
 
To that end... does anyone know which seal is actually supposed to seal the TB shaft AND how it's supposed to actually go in and seal?

The valve stem seal is whats called for I thought and yet here we are. I'm going to (for now) direct swap my TB but my spares come off of my (former) winter beater and while that car ran GREAT, rust and grime have certainly gotten all over everything.
 
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