Throttle body change, vacuum leak?

[chris davey]

The other day I went from a traction control throttle body to a non traction control throttle body on my 1jz. The traction control wasn’t hooked up so the second butterfly never did anything anyway.

Last night I went to start it and it is now not starting. It cranks and starts for a second and then clonks out and you can hear a hissing sound like there is an air leak somewhere.

I didn’t touch anything except the throttle body.

There are 4 outlets on the TB.



The top left one was blocked off before and is now. It lets additional air into the pipe pre throttle plate.

The middle one was always just going to atmosphere as I think that is the one that carries coolant through the TB for cooling or heating. This is by passed on my car.

The black one on the right that is on the top goes to a small circular diaphragm sort of thing and is exactly how it was before.

The bottom right silver one seems to have had coolant in it but not recently. I have hooked this up to where it was before also.

The weird thing is the hissing sound appeared to be coming from the cam covers at one stage. It was hissing for a long time and as I pulled the oil cap off it was like it had finally escaped. This says that there is compression in the sump area and the only way I know that that can happen is if the rings are gone and it pressurizes on the way down. Is this correct?

What I was thinking of doing was doing the boost leak test as described here.
http://www.toymods.net/forums/showth...ght=boost+leak

I figure if it doesn’t leak then it must be at the end of a way one valve as I will be giving it boost whereas it will actually be a vacuum leak.

What do you think?

Thanks

Chris

[chris davey]

BTW blew into the middle one and it is definitely blocked. Can not blow any air out.

[Skip]

Chris the 2 silver ones circulate the engine coolant, which you don't want, so you should probably disconnect them. The top left black one won't make a difference as it's before the throttle butterfly.

Perhaps it's the throttle body flange leaking, did you use a new gasket?

[chris davey]

I used the old gasket as it looked fine to me.

I could disconnect the other coolant line but I don’t think that would do anything?

I suppose I should have a clearer idea of what is happening when I test for leaks tonight.

[CrUZida]

It would have to be a serious leak to stop the Microtech from starting the car, and I mean serious (like bigger than a golf ball).

Disconnect the TPS and see if it starts.

If it still doesn't start look elsewhere.

[chris davey]

thanks mate. WIll try it tonight.

[chris davey]

Compression Results

Date Cyl Dry Wet % Notes
1 120 148 23.33% Tested Dry first, 1-6.
2 120 137 14.17% Then wet, 6-1.
3 120 130 8.33% Cold engine.
4 128 135 5.47% Replaced TB earlier.
5 122 140 14.75% Suspected blowby.
6 120 125 4.17%


So here are my results. The engine was dead cold so I think that may contribute to low numbers. Also, I am actually not 100% sure the guage is accurate as the neighbour who borrowed it returned it saying that it doesn't work anymore. Then I used it and it seemed fine.

I did the boost leak test and found that the blocking plate for the old ISCV spot was leaking hardcore. I am going to get a 1/2" thick alloy one made up tomorrow. I will then redo the boost leak test and see how that goes.

I currently just have a nut with a very small hole in it that is in the spot where the exh cam cover usually vents to the intake. Because this hole is very small I think it is accentuating the blowby theory. We tested it out on my dads 3rz hilux with normal sized pipe and it didn't seem like much pressure comes out of there but through a 1/8" hole it would seem like more. But the weird thing is that I haven't heard it do that before?

[camrygt?]

I don't think any sized vacuum leak would stop it from starting.
For example cranking it with your foot flat and holding it once started should just hit the rev limiter.

Tried holding your foot halfway down? throttle not totally closed? as with microtech installs you usually need to set the stop screw to hold the throttle open a little especially if it doesn't have idle control hooked up.

The idle and running maps in a microtech are usually close enough to the same that it will run ok with or without a tps or any possible tps error.

If it starts and stops straight away check that the fuel line stays pressurised as it stalls.
there arn't many other things that can cause it to do that especially with a microtech.

[chris davey]

Thanks mate.

I totally forgot to even check the air fuel ratio. It doesn't have much time to get a reading though. I haven't got a fuel pressure guage but I know the pump is still pumping after the engine clonks out.

If there is a massive vacuum leak, will that affect the base pressure of the FPR?

[CrUZida]

Yes, but not enough to stop it from starting.

I'd say you have knocked something off while changing the throttle body.

Check for spark, check for fuel, clean the plugs, etc etc.

[thechuckster]

Chris - did you swap over the TPS from one to the other?

[chris davey]

no haven't yet.

Don't know what diff it would make if it doesn't work with TPS plugged in or not though?

[CrUZida]

If it works with the TPS unplugged (Microtech does, I know because I've driven mine with it unplugged, drove the same incidently), but doesn't work with the TPS plugged in, you know where the issue lies.

[chris davey]

nope, didn't work either way. That is why I don't think it will work even if I swap to other TPS.

I can't do anything until I get the new alloy plate made up on Monday to block the ISCV hole.

[chris davey]

Sorted it out yesterday

Got the new plate on there and did the boost leak test and she is all good now.

Plugged TPS back in.

It started and then died. Checked the datalogs.

Then just had to fiddle with the trottle stop screw a bit as I previously had it wound in pretty far. Upped the idle to 900rpm. Good to go and tune again