Gas pressure drop between Tranny Shifts

sd2649 · #1 09-19-2007, 08:54 AM

I've had my SVX for three years now, and the tranny has always done quirky things under WOT. I am going to state everything I know about the tranny, and see if any of yall can help me out

The previous owner had the tranny replaced, TWICE. The first time, the transmission was slipping and not shifting properly, so they replaced it. The old tranny part number was: 31000ab870C1 the new tranny number is: 31000ab870R1. not sure if the R1 and C1 just stand for Core and Rebuilt

Then, It was taken in because, and I quote from the paperwork: "the customer is hearing a flapping noise and noticed the speedometer is not working and the air conditioner stopped blowing cold on the way to town. The noise happens when under acceleration." The shop detected a code, stating that it is the VSS2, they then told the customer that they would have to rebuild the transmission, "as it is an internal part of the transmission". So.... they rebuilt the transmission. The mechanic that put in my new tranny apparently didn't know what he was doing, and it "brakes" only when shifting while under WOT. It has done this ever since he had it replaced, but didn't notice it until a month after he had it replaced (over 6 years ago now). I have ckecked the tranny codes, and all I see is the same VSS2 sensor code, but it has to be functioning correctly, because the above symptoms are gone now!

OK, Here's my two cents on the matter. In this forum:

http://www.subaru-svx.net/forum/showthread.php?t=31895

there is mention of my EXACT problem, the issue shows its ugly face, when a member REPLACES his TCU with one from another vehicle. The 4 second "braking" while the tranny shifts from first to second, and the 2 second "braking" between 2nd and 3rd. NOTE: this ONLY happens while under full WOT, if you pull back just a couple degrees, the tranny will shift BEAUTIFULLY between every gear, no problems whatsoever. I have noticed, that if I have the car ignition on, engine NOT running, when I depress the throttle, I hear a click noise right where I have to pull the throttle to in order to have it shift properly. Is this a WOT sensor or something?????? There was noted on the previously linked forum, that the issue was linked to the engine cutting off fuel to half of the cylinders between WOT shifts. If so, then the forum also states that there was a way to stop the engine starving the engine for fuel in between shifts, if this is doable, it should fix my problem, right??? someone help me please!! I don't want to have to buy a new TCU just guessing that it would fix it somehow. Someone help me please!!!!!!!!!!!

-Steven

Trevor · #2 09-19-2007, 04:28 PM

Your report regarding what appears to be a clicking near WOT gives an interesting clue, particularly as no one appears to have previously investigated the Throttle Position Sensor. This component is a very likely culprit according to your described problem.

You should check the TPS, and the mechanical operation of the complete throttle system and locate the click. Refer to my notes in the how too section under TPS checking and cleaning.

Best of luck and report back as your experience will be of interest to others.

sd2649 · #3 09-19-2007, 09:32 PM

it's not the TPS, it's a click from farther underneath, it sounds exactly like a relay switch popping on and off, not felt in the throttle at all. It has to be electrically actuated. Try it, sit in your SVX, turn the ignition ON without starting the engine, then push the throttle, and listen for the click, bet yours does it too!!! Also, I replaced the TPS already, mine was worn where it sits at highway speeds and was causing the lock up torque converter to turn on and off sparratically.

sd2649 · #4 09-21-2007, 07:52 AM

I listened for where the click was coming from, and couldn't identify it from under the hood. Either it only makes it when pushing the gas petal, or it us on the inside of the firewall. I listened closely while pushing the throttle on the throttle body, and the clicking is not present. When sitting in the car, I still hear it loud and clear. I am going to have my wife sit in the car and press the gas while I listen up top. Then if I don't hear it, I'll have a look under the dash. Either way, Does anyone know how to disable the pause in throttle between engine shifts? It had been mentioned by a member in the thread that I mentioned earlier. I PM'ed him, but he hasn't responded, and it looks like he hasn't been logged on for a while. Please, anyone, help me!!

crazyhorse · #5 09-21-2007, 10:35 PM

As usual, I'm not SVX savvy yet, but I can tell you that both my XT's and my 97 Legacy have a switch on the throttle that disengages the A/C at WOT. Yes it makes an audible click.

Now I dunno if this switch would cause the switchover to the WOT map in the ECU or not. However, IF it does, this could be the root of the trouble. I'd think the engine might lean out if the WOT map wasn't being used. That would cause a loss of power, as the knock sensor started pulling out timing

Trevor · #6 09-21-2007, 10:35 PM

Report back when you locate the click noise as this does not appear to be normal and should disclose the essence of your problem.

The pause between shifts involves the ECU and TCU and control via the ignition and it can not be readily disabled.

sd2649 · #7 10-02-2007, 12:04 AM

OK, I have not detected the exact location of the clicking noise, but I did take my intake apart today. Took off the throttle body, cleaned it up and sprayed the intake manifold down with some carb cleaner. I also took the resonator out of the fender, cut it up, put it back together, and have true ram air coming in through the wind diverter in front of the wheel. I'll have to post a pic later. While the throttle body (and TPS) are off the engine, I'll go poke around and see if I can get anything to click. I was also wondering what the second sensor bolted on the bottom of the throttle body did. Is it an idle control of some sort?? cold idle, warm idle?? It is adjustable, I was wondering if it could help me out with any problem I have.

sd2649 · #8 10-02-2007, 01:14 PM

OK, lets go back to yesterday. I had a perfectly running SVX in my driveway. Had a code 29 (crank angle sensor2) but no CEL showing. The SVX would idle kinda high on cold starts and shifts would be delayed at WOT. So.... I decide to take the throttle body off, clean it out, check the TPS and so on. While I had the throttle body off, I sprayed the intake manifold with some seafoam. I disconnected the little white wire connector that goes to the sparkplugs and turned over the engine a while just to clear out the seafoam. I spent a while messing with the baffle in the fender well (made a ram air intake out of it) and then called it a night (of course bringing the throttle body and other misc. parts inside).

Ok, this morning. I put the throttle body back, put the TPS back in the exact same position as earlier, hook up the intake and start the car. This is what I get for my trouble:

*The car starts into a high 2000rpm idle, a little rough and then smooths out around 1600rpm. Then the CEL comes on. I check the codes and this is what I get: 11 crank angle - 21 water temp - 24 bypass air control - 29 crank angle2 - 31 TPS - 56 EGR

*Sooooo.. I pulled down the idle with the bolt stopper to 1000(low as it would go) and take it for a drive, Good news is that the engine semms really responsive, I wouldn't say any better, but it REALLY is NOT any worse. The good news is that It didn't hesitate on the first run, so I did SOME good. So, I get on the throttle to clear it out, and it shifts at 3500rpm ALLL THE TIME. I floor it, and it shifts at 3500 without going above it. Honestly I don't know what could have caused so many code at once. Is there some master plug that could be disconnected? also, the tranny shifts REALLY hard, we're talking whiplash here.

Is this something that happens under "limp" mode?? could the high number of CEL's be causing this?? If so, why is the engine running so well??

PLEASE HELP!!

sd2649 · #9 10-02-2007, 01:28 PM

Good lord, I messed up something. It now has multiple CEL's and shifts hard at 3500 all the time under WOT. The details are in this thread:

http://www.subaru-svx.net/forum/showthread.php?t=41036

Someone please help!!! what to do??!!?!??

Hocrest · #10 10-02-2007, 01:43 PM

First, the TPS is way to sensitive to adjust it by lining up a paint mark. I just wen through this today. Use a voltage meter and adjust it to .5 volts.

Trevor has a good right up on adjusting it, here in the How To Doc's

That is probably affecting the high shifting and the idle.

For code 24, that is plugged in on the bottom of the throttle body, are you sure it was plugged back it tightly when you replaced the TB?

I'm not sure what caused 11, 21, 29 and 56???

sd2649 · #11 10-02-2007, 02:27 PM

OK, I tried to clear the CEL codes, and it won't let me, when I plug the wire in to clear, it still gives me the CEL for the TPS, so it must be the problem. I go check on the TPS and notice that it isn't plugged in all the way. I set it as close as I could to .5volts (it changed every time I tightened it down, is .45v good enough?) I then proceeded to start the car and voila! no CEL. I will pull the codes in a minute to see if anything is lingering without putting up a CEL. I will also let you know if it shifts properly. Even though no CEL, it was idling aroun 1600rpm, so I pulled the idle stopper back a little. This is curious seeing as it would idle at 900rpm before with the same idle setting. I must have cleaned up something that was restricting air flow for it to idle so high.

Just me thinking, but being it wouldn't let me clear the codes with the TPS unplugged, maybe it is still throwing old codes for everything else while I had them unplugged and was turning it over??????

P.S. what are the stock setting for idle warm/cold?? 650/850????

sd2649 · #12 10-02-2007, 02:56 PM

WEIRD!!

So, now the car runs PERFECT! it is better than ever. The only weird thing is that even though it doesn't show a CEL anymore, it still throws codes at me when I read them, AND they're the same codes!

11 - Crank Angle Sensor/Circuit
21 - Coolant Temperature Sensor/Circuit (PS my temp sens works in dash!)
31 - TPS (It is installed as it should be!)
24 - Air control valve
29 - Crank Angle Sensor #2
56 - EGR system

If I'm not mistaken, it would be running POORLEY if all this were true, soooo..... why can't I get the codes to clear???? any ideas???

Nomake Wan · #13 10-02-2007, 03:56 PM

If both 11 and 29 are true, you shouldn't have a working tachometer and the engine should probably die. Since those are both crank angle sensors...

I can't clear my codes either but I suspect they're true. Will be interesting to see what comes of this.

sd2649 · #14 10-02-2007, 04:28 PM

I agree, they must be working properly, seeing as the engine is running so well. It is interesting to me that all the codes thrown were items affected when I had everything apart.

Wiring harness: Both Crank angle sensors / Water temp sensor
Throttle body/ intake hose: TPS / EGR / Air Control Valve

However, other codes should have been thrown too; like the MAF or a hundred other things that are run off of the vaccuum lines.

Also, I was wondering if we might have some of the same codes, maybe certain ones tend to "stick around" until they run properly for a certain amount of time or something. What codes are you throwing and how long have they been unclearable Nomake Wan?

Maybe we're doing something wrong as far as the method to clearing the codes?? although I have cleared codes correctly before!

ON ANOTHER PLANET:

with the TPS affecting the Transmissions shifts I was wondering if there was someway to tweak with one of the crank angle sensors and adjust when the tranny shifts. I know that there are guys around that would love to raise the WOT shift points of their tranny to somewhere around 7250rpm or so. Just thinking out loud, probably couldn't be done because of something I know nothing about

Trevor · #15 10-02-2007, 07:33 PM

Quote:

Originally Posted by sd2649

Even though no CEL, it was idling aroun 1600rpm, so I pulled the idle stopper back a little. This is curious seeing as it would idle at 900rpm before with the same idle setting. I must have cleaned up something that was restricting air flow for it to idle so high.

N.B. The idling speed is not set by means of any adjustment relative to the throttle position and is dependent on the ECU. The throttle linkage should be set so that the throttles are completely shut/closed, and if anything a little free play in the linkage should be provided.

If you have the throttles set slightly open, the TPS will not be set correctly. You should have noted that my instructions include the following:-

"1. Connect all connectors. 2. loosen TPS fixing screws. 3. Turn ignition on. 4. Adjust TPS position while throttle valve is confirmed FULLY closed, to specified voltage, using a volt meter. 5. tighten fixing screws.

The voltage is specified as within a tolerance of from 0.45 to 0.55 volts. You should have no trouble in setting things at exactly half a volt."

You should note that for good reason, "FULLY" is/was emphasized.

You must set everything correctly first off, as an absolute must.