Hi folks,

a little while ago, i was complaining of problems with my Idle Switch in the TPS...Having resolved (well tested the switch satisfactorily anyway) that issue, one of the cars symptoms still remains.

 

At anywhere between 35 and 50 mph, if you take your foot slowly off the thottle until its almost completely off....(Coasting along a long flat road for example). The engine revs will kick up and down between 1500 and 2100 rpm (@35mph). So pull your foot off a fraction too far and it drops to 1500 and then apply the throttle a little and str8 back to 2100...

 

Now its not kicking up and down gears, as dropping out of D into 3, results in 2400ish..

 

So its like the torque converter kicking in and out or something.

 

My basic question is, is this likely to still be a problem in the TPD or another sensor or something wrong with the Torque Converter.

 

Any tests or places to start with this diagnosis would be appreciated.

 

One thing i would like to understand, is how does the ECM interpret the idle switch at speed. If for example, throttle position is switching between idle switch on and idle switch off, what does the ECM actually do..

 

Also, tried setting the cruise control...Speed sits rock solid at 35Mph, but the revs slowly (and sometimes not so slowly) drift between 1700 rpm and 2000rpm...and the car has this awkward surging sensation to it.....:-(

 

hope someone can help :-)

 

cheers

Andrew

Sounds like a possible issue with the torque converter lock up solenoid.

 

How many miles are on the car/tranny?

 

Honestly, once these trannys reach a certain point.....they're just going to have issues....not much you can do about it, other then get a lower mileage one, or rebuild the current one.

The car has 238000km, but i had the tranny rebuilt only about 20,000km ago (i dont think they touched the torque converter though). Worst part about it is, the place that did the rebuild (they do a lot of Subarus) is an hour and a half away, so i cant just drop in and let them have a drive :-(

 

I just checked and there are no current codes on the Tranny, but it is reporting Vehicle Speed Sensor 2 as a Previous code... I have no idea if that would contribute to the problem.

 

Thanks Josh for your comments..

Yes, that could be fouling things up.

 

The VSS2 is in the dash, and controls the speedo, etc.

 

I had the base cable from the tranny go on mine, so no speedo. Without a speedo reading the ECU does not know when to engage the lockup on the torque converter. I had very similar issues on mine.

 

Clear the ECU & TCU and see what happens.

I will give it a try, can the TCU be cleared by pulling power from the battery for a while? Or what is the best way to clear the TCU?

 

cheers

Andrew

Pull fuse 14 it's in the fuse panel under the dash on the driver's side. It's labeled EGI/TCU. Pull that fuse for 15-30 min. That will clear both ECU & TCU.

 

here's fuse box diagram

http://www.main.experiencetherave.com:8080/subaru_manual_scans/1990_Legacy_Owner_Manual_Scans/119.jpg

 

and fuse listings

 

http://www.main.experiencetherave.com:8080/subaru_manual_scans/1990_Legacy_Owner_Manual_Scans/118.jpg

Thanks,

Ok, i have reset the computer, and now i will wait a while and see what happens...

 

One question i do have though, is does the '90 have two speed sensors of just the one.

 

According to the codes on your site, it was pulsing code 33, which is vehicle speed sensor 2...According to my manual wiring diagram there is no speed sensor 2 in the '90 to 94 models, and the one that is there, is only in the cruise control circuit...

If there is a Speed Sensor 2, is it located at the same place on the speedo..?...If it only has one, then what is code 33? :-)

 

If you folks havnt guessed i have been putting off dealing with a heap of issues in my soobie and now im in a mood to sort out all the gremlins :-)

 

cheers

Andrew

Yes it has two speed sensors.

 

Speed sensor 1 is in the tail shaft of the transmission. It reads the output speed of the rear wheels/driveshaft.

 

Speed sensor 2 is in the combination meter in the dash, which measures speed from the front diff, and also displays speed on the speedo.

 

The tcu, then uses both of those readings to determine how to adjust the AWD transfer.