Gas pressure drop between Tranny Shifts - Page 3

Trevor · #31 10-05-2007, 05:24 PM

Quote:

Originally Posted by sd2649

any luck with that revised method to clearing your codes? It still didn't work for me.

The data I quoted was from manuals for right hand driver seating cars.

Nomake Wan · #32 10-05-2007, 07:24 PM

Didn't try it actually, since I actually reset my ECU recently. I figure resetting the whole thing will clear the codes outright, but I haven't actually plugged the lead in to see.

sd2649 · #33 10-06-2007, 09:48 AM

how did you do that? what do you mean by COMPLETELY resetting the ECU? pull it out? disconnect the battery terminals?

Nomake Wan · #34 10-17-2007, 02:33 AM

Quote:

Originally Posted by sd2649

how did you do that? what do you mean by COMPLETELY resetting the ECU? pull it out? disconnect the battery terminals?

Sorry for the super-late reply, I've been away. I removed the negative battery terminal for about two hours. It was for an experiment related to Phil's ECU Dump project. Since the "working values" were reset by this and since my error codes vanished, I assume that this is a complete reset method.

But then I hit a bump and check engine and now I have a code 37 again. Tch.

The Code 11 is gone though.

Myxalplyx · #35 10-19-2007, 06:01 PM

I have been reading your threads off and on. Wish you good luck in resolving this matter. My car actually shifts fine but I don't think it is acceptable for flat out speed and such. The clutchpacks shifts to slow for me and that generates heat. Will be looking forward to you coming to a conclusion on this matter. Good luck!

sd2649 · #36 09-15-2010, 06:51 PM

Ok guys. I still have the shifting problem at wide open throttle. My output shaft recently sheered, so I recently had it rebuilt. I told the shop of the issue and they assured me it would get fixed. Well, I still get a vss2 error and my engine still cuts off throttle for a whole 2 seconds at wide open throttle during shifts. Also, the first time I pull out of the driveway every morning, the car stays in 1st gear for entirely too long. Not mechanical, this is after the rebuild.

To recap, I have a fwd 94 that had its tyranny swapped by a shop 7 years ago. Since then it has done this weird shifting thing. With the advent of the new shift control mods out, I was hoping more light had been shed on this subject. So... why does a fwd tyranny need 2 vss's?

NiftySVX · #37 09-15-2010, 07:28 PM

I stumbled across your thread. I can help you with a number of things.

The Click you are hearing is the Magnetic clutch on the compressor clicking off. This is not a switch. It is an output of the control system. You would have to change the computer program to change it.

The screws on the throttle body are calibrated at the factory. If you adjust them, the correct repair procedure is to replace the throttle body as it is calibrated at the factory. The Stopper screw for the blades themselves is one of these, but you can usually fix it. Never ever touch it. It does not EVER require adjustment.

You are thinking about the engine control system as a bucket of parts, remember it is a system. Inputs->processing->output. Changing the cam angle sensor will cause an unknown problem with the system ALL of the inputs are used TOGETHER to process an OUTPUT. Don't do it. The engine very briefly changes the pulse of the injectors, and causes a reduction in power output between gear shifts. It should not be thought of as a fuel issue, it does nothing with fuel pressure or volume. Only the injector "skips a beat". this happens all the time, not just at wide open throttle. A change in any input to the control unit will not change the output, only cause problems.

It only has one speed sensor for FWD. The one that reads off the differential side case via a gear. It is called NO.2 because in AWD the rear one is NO 1. However, there is no NO 1 in fwd. Keep in mind this transmission was designed for AWD and then a variant was made for FWD.

FWD ecu is installed in your vehicle. If there were an AWD ecu installed it would show all kinds of codes for the missing parts it wants to see in the AWD unit like the duty c solenoid and speed no 1.

You need to make sure that you have a TCU for an SVX and a transmission for an SVX. I think I remember this problem happening when a TCU from a legacy was used in a SVX. Or maybe it was an SVX tcu in a legacy. Respond with the part number written on your TCU.

sd2649 · #38 09-17-2010, 09:40 AM

Thanks for stumbling! I will get the part number as soon as I can.

sd2649 · #39 09-21-2010, 09:46 PM

Well, amazingly enough... the FWD tranny apparently does have 2 vehicle speed sensors. Apparently I had a wiring problem going to the rear vss. That vss is INSIDE the tranny... Got the wire fixed up and BAM smooth shifts at WOT. It shifts a little bit later on all the time too. Very nice to have my car back to normal!!

So.... why on earth do they have the second VSS?? And why on earth is the ecu/tcu using both for shifting info.... so weird!

NiftySVX · #40 09-22-2010, 09:36 PM

I'm going to have to look this up. Maybe I drink too much but i really don't remember that back sensor being there... what color was the wire you repaired?

sd2649 · #41 09-22-2010, 09:42 PM

I will have to look. I had a shop repair it, but they pointed out the wire harness that they tapped into. Hopefully I can discern which one it is that the fixed. Also, it is INSIDE the back part of the tyranny, so it should be fairly well hidden. Like I said in a previous post, the previous owner had this sensor replaced ( I have paperwork from it) and in that paperwork, it says that they had to remove and open the transmission to repair it... the $4000 bill from 10 years ago proves that they fixed SOMETHING.

sd2649 · #42 09-22-2010, 09:45 PM

I still don't know why it would have 2 vss's... maybe to allow for the use of one transmission computer? Is an awd tcu different from an fwd tcu??

oab_au · #43 09-23-2010, 05:45 PM

That speed sensor may be in the case reading the parking pawl rota. Like the one in the Euro AWD gearbox.

Why? Maybe it is to detect wheel spin, if the out-put shaft and the diff sensor don't read the same, it cuts power. I always thought that there was something, in the FWD box's that prevented them from blowing up the front diff, if there was some wheel spin, that is lacking when the AWD looses the rear drive to blow the front diff.

Harvey.

NiftySVX · #44 09-23-2010, 06:49 PM

Harvey you are describing traction control, but unfortunately the only subaru that had that in 2WD form was a VERY few 1995 only legacy L and LS, as an option. I always thought it was odd that it was not offered on the 94 LS SVX or the 1995 L 2wd models. I can almost promise you there is no rear speed sensor, the one in the AWD reads off the output to the rear drive which is not there. I will have to look at my wiring diagrams again when I get to them. The reduction gearset in the back of the 2wd has no place for the speed sensor to read.

sd2649 · #45 09-23-2010, 06:55 PM

Found the wiring... it makes sense what oab_au is saying... when the sensor wasn't giving a reading... it cut power to the engine during all shifts at full and nearly full throttle... sounds like a good way to keep the tyranny from exploding the diff to me! No, its not traction control (no braking... blah blah blah) but it would save the diff.... either way, this sensor, which is there, was definitely cutting fuel to the engine during shifts...