R33 GTST TPS DROPPING

[armog]

Link PNP in stock harness. Series 1 RB25 5 speed

Issue is that at around 3200rpm the TPS % drops to 0% causing a cut of throttle until more or less throttle is applied. Occurs intermittently but always in 1st gear, taking off from a stop. TPS analog values show 0.47 closed and 3.70 open, I have recalibrate the tps multiple times but issue persists. I have checked and the tps rises and lowers with throttle smoothly in voltage and position. 

I have attached the .pcl and log.

Issue can be seen at 21:17 in the log. 

tps logs.pclr tps logs.llg

[Vaughan]

Can you get a log with the analog 3 voltage, analog 3 status and 5V out in it? The more variables the better but specifically those three would be nice

[armog]

AN 3 and 5V OUT.llg

[Vaughan]

From that second log it looks like the TPS value is tracking the voltage correctly.

I can see a few sections where the MAP value seems to increase with no visible input from the throttle or idle controller, are these sections where the issue is?

I would be tempted to suspect the TPS sensor is faulty

looking at your first log again comparing the map and tp values at 21:17 it looks like the throttle is physically closing as you can see the dip in the MAP pressure at the same time

[armog]

50 minutes ago, Vaughan said:

From that second log it looks like the TPS value is tracking the voltage correctly.

I can see a few sections where the MAP value seems to increase with no visible input from the throttle or idle controller, are these sections where the issue is?

I would be tempted to suspect the TPS sensor is faulty

looking at your first log again comparing the map and tp values at 21:17 it looks like the throttle is physically closing as you can see the dip in the MAP pressure at the same time

I'm running an aftermarket manifold thats drive by cable still. The map pressure drop i want to say is attributed to the loss of throttle input and the engine shutting off maybe? The extra connector i assume is for an automatic. 

[Vaughan]

That grey connector is for idle and full throttle switch (neither is used by the Link), the tps in my stagea has two plugs, one for grey and one for brown. map pressure decreasing means more vacuum, if the engine was dying I would expect pressure to increase as it used less of the air coming in. On my S2 motor there were 3 different air valves, one for idle, one for when ac is turned on  (the ac also turns on a fan) and then there was a 3rd one bolted the water pipes on the bottom of the manifold but I haven't figured out what that one did yet.

I can't see any cuts being applied in that second log

Are you sure there isn't an issue with your throttle cable? Is the engine leaning under load affecting the the throttle position?

Unless you're using TPS as your fuel or ign load the tps value shouldn't make a difference to your engine power

 

[armog]

1 hour ago, Vaughan said:

That grey connector is for idle and full throttle switch (neither is used by the Link), the tps in my stagea has two plugs, one for grey and one for brown. map pressure decreasing means more vacuum, if the engine was dying I would expect pressure to increase as it used less of the air coming in. On my S2 motor there were 3 different air valves, one for idle, one for when ac is turned on  (the ac also turns on a fan) and then there was a 3rd one bolted the water pipes on the bottom of the manifold but I haven't figured out what that one did yet.

I can't see any cuts being applied in that second log

Are you sure there isn't an issue with your throttle cable? Is the engine leaning under load affecting the the throttle position?

Unless you're using TPS as your fuel or ign load the tps value shouldn't make a difference to your engine power

 

When I look at the wideband it does go lean yes, the throttle cable is the factory cable, I had to remove the pedal stop or the throttle body wouldn't open all the way, pretty sure I'm using MAP as load. Whats weird is it doesn't do it 70% of the time. 

[Vaughan]

Interesting that you are using the factory cable, as my factory Stagea cable isn't long enough to reach when using a greddy style manifold.

I suspect the lean patch is due to the overrun fuel cut. I've just noticed that the overrun fuel cut doesn't seem to show up under the percentage FCut runtime and if your throttle is dropping to 0% that cut will be being applied.

It really does look like the throttle plate is being physically shut. Does it happen only under hard load?

[armog]

12 minutes ago, Vaughan said:

Interesting that you are using the factory cable, as my factory Stagea cable isn't long enough to reach when using a greddy style manifold.

I suspect the lean patch is due to the overrun fuel cut. I've just noticed that the overrun fuel cut doesn't seem to show up under the percentage FCut runtime and if your throttle is dropping to 0% that cut will be being applied.

It really does look like the throttle plate is being physically shut. Does it happen only under hard load?

It does not happen under hard load, only under very light load when taking off from a stop or a light. I was able to use the factory cable by routing it differently. I can try an s14 cable as its longer and use the other location on the throttle body and see what happens as well as a new tps. 

I also noticed the throttle cable is different between my friends r34gtt (longer).

Edited May 1, 2020 by armog
additional information.

[armog]

On 4/30/2020 at 8:54 PM, Vaughan said:

Interesting that you are using the factory cable, as my factory Stagea cable isn't long enough to reach when using a greddy style manifold.

I suspect the lean patch is due to the overrun fuel cut. I've just noticed that the overrun fuel cut doesn't seem to show up under the percentage FCut runtime and if your throttle is dropping to 0% that cut will be being applied.

It really does look like the throttle plate is being physically shut. Does it happen only under hard load?

So i replaced the TB andd TPS and issue still persists, further testing shows that the throttle body itself may be the issue. the throttle body never seems to return tps voltage and position back to the same position, and about 5 percent movement is required to register on the tps. TB is appearance wise a generic 90mm TB and another friend of mine with the same type of TB also on link has the same issue with his 1jz car. now the question is wether to go oem with a q45 TB or something else.

[Adamw]

Pull the TPS off the throttle body and check how it couples to the throttle shaft.  I have seen some that have lots of backlash and a non-spring loaded TPS.  A dollop of silicone or similar may be all it needs.

[armog]

39 minutes ago, Adamw said:

Pull the TPS off the throttle body and check how it couples to the throttle shaft.  I have seen some that have lots of backlash and a non-spring loaded TPS.  A dollop of silicone or similar may be all it needs.

I assume your referring to a sloppy fit between the shaft that the TPS is actuated by and the TPS yes? The TPS  is a new oem RB25 series 1. I see what you mean, the tps is not spring loaded. 

By a dollop you mean to put some silicone gasket maker on the shaft to make up the slack correct? Upon removal the supplied adapter indeed has a horrendous amount of slop. Over 10 thousandths indicated by the dial gauge.

[Adamw]

1 hour ago, armog said:

I assume your referring to a sloppy fit between the shaft that the TPS is actuated by and the TPS yes?

Yes.

1 hour ago, armog said:

By a dollop you mean to put some silicone gasket maker on the shaft to make up the slack correct?

Yes on the shaft or in the hole to take up the play.

[armog]

3 hours ago, Adamw said:

Yes.

Yes on the shaft or in the hole to take up the play.

So I measured the tolerances of the oem TB and compared it to the aftermarket one and decided to make a shim to take up the play and used a 0.35mm shim(made from a feeler gauge). The issue is no longer present and the throttle is a lot more responsive. Thank you for the help and the support, very appreciative of the direction to fixing this issue.