Issue with boosting, possible boost leak?

[Supra mn]

Background: 1989 7m-gte, automatic, BPU (turbo back exhaust, intake, bosch bpv, AEM Truboost set to 11.5 psi)

I can't seem to find this boost/vacuum leak. I can hear something at idle, and its on the driver side around the throttle body, but might be back behind the engine on the intake side.. its hard to tell.

Ive sprayed soapy water on all the IC pipes, up to the TB. I pressurized the system to 20 psi from the turbo inlet to the end of the 3000 pipe. No leaks whatsoever. I don't believe its the TB gasket either.

I sprayed starter fluid in damn near every place I could think of while the engine was idling, and there was no change in rpms.

I pressurized the whole engine up to around 12 psi, and couldn't find much else than the egr vacuum modulator and the tps bleeding air. It was somewhat hard to listen, though, since air was just flowing through the engine.

I just had a Coolant/Heater line break and spray coolant, but that was only under boost. I replaced it, (it was the one running from the valve by the charcoal canister to the top of the cylinder head) and no longer have a coolant leak.

Under WOT, I usually hit 11.5 psi through all gears. Now, I only hit 8.5 psi in first, spikes to 10 in second but quickly back to 8.5, and spikes up to 12.4 in 3 (without O/D on) and once again, quickly drops back down to 8.5. I have the truboost set so it will light up red as an alarm at 12, but it doesn't alarm me when it spikes up for some reason.
My idle is between -12 and -17, usually closer to -12. (now averages about -15 with the new injector insulators/O-rings and 3000pipe couple/t-bolt clamps)
My Tru-boost "A" setting is hitting 7.5-8 psi, "B" is 8.5 psi, and "OFF" is 7.5 psi.
I just installed a wideband, so if those numbers will help, I can get them. I know its between 14.7-15.3 at idle and like 10.4 under WOT.

I just bought a new boost solenoid as I thought the old one was malfunctioning, but that wasn't the problem.

I have a 2.75" coupler with t-bolt clamps, injector o-ring kit, and TB/ISC gaskets. Just installed them, they didn't help much other than a slight vacuum at idle increase.

I have a full intercooler kit ready to be put on, but I would like to wait until I find this leak before installing as I know this will mess with the boost settings, and I would like to know 100% that the leak is fixed.

I've searched the forums, google, TSRM, everywhere I can think. Just cannot find this leak for the life of me..
All help is appreciated!

 

[hvyman]

Sounds like a vac leak not a boost leak.

Tps shouldnt be bleeding air either.

Going to have to go over all the gaskets. Make sure the egr gaskets are good, intake manifold gaskets, tb gasket, and all vac hoses.

 

[jetjock]

Crack me up. Maybe there is no leak...

 

[3p141592654]

I'm with him! What boost leak?

 

[Supra mn]

Maybe the tps wasn't bleeding air, I don't remember if it was coming from there or that general area.
I replaced the TB and ISC gaskets today, along with the 3000-TB coupler and clamps. I also replaced the injector insulators, O-rings, etc. with the injector kit from DM.
Vac hoses are all good, I've traced every one of them.

Crack me up. Maybe there is no leak...

Maybe there isn't. But what else could it be? Nothing has changed, boost settings are exactly what they were previously.
And no, it's not a mental "I don't feel as much power as before" problem.

 

[Supra mn]

After reading a code 41 and finally buying a multimeter and feeler gauges, here are my numbers:

0mm VTA-E2: 1 (infinity, there was no deflection/movement on the multimeter)
less than .5mm IDL-E2: 047-055, multimeter at 2k, feeler gauge of .483mm. With a .508mm gauge, it read 1.
.9mm IDL-E2: 1 with a .889mm feeler gauge, and also 1 with a .483+.457 together. (didn't have a .9mm+ gauge)
Throttle fully open VTA-E2: 5.0 set at 20k
VC-E2: 6.38 also set at 20k

These comply with what the tsrm requirements are, but the infity with no feeler gauge is throwing me off.
Do these numbers seem correct? And if so, why else would I be throwing a code 41?
Could this have any effect on the lack of boost I'm seeing?

Bare with me, electronics are kind of my weak spot, and using a multimeter is new to me.

 

[jetjock]

Other codes? Maybe a 51 all the time or just when the pedal is slightly pressed? If so, which?

You should not have infinity with the throttle fully closed. Should be the opposite: low resistance.

Code 41 is caused by one of three conditions:

1) VTA less than 100 mv (VTA is shorted to ground in TPS or wiring)

2) VTA more than 4.8 volts (VTA is open circuited in TPS or wiring)

3) VTA exceeds 1.5 volts with IDL connected to E2. (IDL remains shorted to ground when throttle is opened.)

That said none of this should have much to do with your boost issue. It should still be fixed though.

 

[Supra mn]

Jetjock, thanks for the info.

The check engine light has never came on, other than about a year ago when I was hitting fuel cut before I had the boost controller.
That being said, no other codes have been thrown. 41 is the only one that shows.
I can go re-read the codes and slightly press the pedal while doing so if that's what you mean, but i'm assuming you meant that while driving.

I tested the clip that connects to the tps to see if my multimeter was even working, and it read out some numbers, not sure if they meant anything though... haha
Anyways, is there a link as to how to fix this? I haven't seen too threads about this code. If not, could you send me a PM with some info on how to test/fix this? The info you provided is great, but I honestly have no idea what it means in regards to fixing it..

 

[jetjock]

...I can go re-read the codes and slightly press the pedal while doing so if that's what you mean, but i'm assuming you meant that while driving....

That's what I meant. Not while driving. Why would you think that? Using the MIL to output codes and having it come on when a fault occurs are two different things.

 

[Supra mn]

Just me overthinking things.
Well, you were right! Code 51 appears while depressing the pedal during code reading, and 41 is still there as well.
No IDL, NSW, or A/C current to ECU during diagnostic check.. with one of the possible trouble areas being the tps.

So this means bad wiring, short, etc. somewhere between the TPS and the ECU?

 

[jetjock]

The 51 means part of the TPS, the part associated with the feeler gauge stuff and *unassociated* with code 41, is working.

This however....

...0mm VTA-E2: 1 (infinity, there was no deflection/movement on the multimeter)...

...isn't right and and needs to be investigated. There should be never be infinity between VTA and E2 regardless of where the throttle is.

 

[Supra mn]

Hmmm, that's what was confusing me, and what was making me think my multimeter wasn't working. (since I tested those two first)

I'm assuming this is what is throwing my code 41 then; how can I investigate this? Or would buying a new tps and adjusting it be a smarter decision?
And i'm a little confused on the code 51.. Is that just to show that part of the tps is working, or is it a whole different problem area in itself?

I know i'm not the first person to experience this problem, I just cant seem to find any good information on fixing it.

 

[jetjock]

1) Unsure of why the corn-fuzion. The TSRM is pretty clear.

2) The TPS is obviously a wear item. Wouldn't hurt to replace it no matter what. Something is goofy with yours though.

3) 51 can be used to show the idle signal portion of the TPS is working. It can also be used to show the AC and neutral start switch is working but that's another story.

4) I suspect it's not the multimeter. More likely operator headspace error...

 

[Supra mn]

I did a little searching and found your write-up on code 51. When the TPS connector is jumped between IDL and E2, code 51 does not appear when reading codes, even with the pedal depressed; just as it shouldn't.
When I measured between IDL and E2 on the TPS itself, I came up with 013 ohms.
I also tried turning the AC on and putting it in R when checking codes, both times code 51 appeared, so the wiring there is good. But like you said, that's another story.

So, should I remove the TPS and see if I can find a problem, or should I just replace it altogether? If I can remove it and fix it, that'd obviously be my first choice. But if something is "goofy" with mine, I'm guessing it's not going to be a simple fix.
Or would simply adjusting the TPS fix this problem?

Corn-fusion, Nebraska.. Punny guy huh? Haha