4EAT Cutting Revs, Overrevving. Please help. JDM UK owner

[brendan]

Car: JDM Legacy GT [EJ20G] 4EAT 1992

Sorry for jumping on the forum and asking questions already, but this problem is going to make me go insane.

After much searching of this forum, i cant find anyone elese with the same problem.

I have just bought the above car, JDM Import, with 54K miles.
It has been sat in a garage for 5 years, and only been used by an old guy for the last 5 months.

Anyway, The problem:

When in 'D' and flooring it, box changes between 3/4th rapidly, cutting revs down to zero while doing so. when it tries to grab a gear, the rev's race round to the redline.

Driving slowly, the box is fine - if i feather the throttle - i can make it go very fast without fuss.

1, 2, 3 are pretty much OK - Although the kickdown is ULTRA sensitive. Its quite hard to drive without it jumping gears.

I've changed the fluid tonight - its a bit smoother. But still feels as if something is wrong.

We dont have many Auto's here in the UK - so me and my buddies are all at a loose end. Can any of you guys/girls help?

To sum it up:
- When flooring it, car overrevs, and cant figure out what gear it wants to be in (Surging around while doing to)
- Performance is 'cut' @ 5Krpm
- I also suffer from torque bind while turning tight & slow.

Whats going on?
How can i fix it?

Thanks in advance, for any help.

Oh - the car is not modified - its totally stock.

[Legacy777]

Wonder if the TPS may be out of whack...

[brendan]

Wonder if the TPS may be out of whack...

Hi Josh, Thanks for the reply

I studied your site also, brilliant resource.

You think that may be part of the problem? I'm guessing the TPS is located somewhere externally and not inside the box itself.

I just feel as if i'm at a loose end, i dont want to begin to spend heaps of cash replacing stuff if the box itself is on its way out.

The box has been replaced before, and i can see it's clearly new (still got stickers on it and whatnot), thats what leads me to believe that it cant be dead, as the whole car is basically showroom condition.

Any more ideas will be greatly appreciated.

Thanks again man

Brendan.

[wtdash]

Did you try pulling the tranny codes? HEREis the USDM method (thanks to JC).

The TPS is on the throttle body/intake.


54K and a new tranny? And torque bind? That's unusual.

Do you have the FWD fuse option under the hood, by the passenger (or maybe driver's side in UK)? If the torque bind goes away it's the rear clutch pack; if it has no affect it's the Duty C solenoid.

Much info on HERE.

[Legacy777]

The TPS if bad can cause some issues with downshifting/upshifting on the trans.

Here are some scans from the US factory manual which tell how to test the TPS.

http://main.experiencetherave.com/subar ... sting1.jpg
http://main.experiencetherave.com/subar ... sting2.jpg
http://main.experiencetherave.com/subar ... sting3.jpg

This may also be of help

Code: Select all

http://main.experiencetherave.com/subaru_manual_scans/1992_FSM_(Engine_&_Electrical)

[brendan]

hi guys,

Thanks for all the info, at the very least - at least now i have somewhere to start.

Yeah, its unbelieveable that the car has already had a new tranny at 54k, and is Torque binding. The car has been sitting, un-used - for 5 years, this may have has some effect on the sensitive parts inside the box, i'm not sure.

I'll take all this info away now and begin to perform some tests. I have a new TPS on its way just to be sure.

I'll let you know how i get on, in the meantime - if anyone else has info, whack it on here.

Thanks for the help so far boys, absolutely legendary.

Cheers
Brendan

EDIT:
No tranny codes or CEL's, which also worries me.
& yes, i do have the FWD fuse thingy under the bonnet - i'll give that a shot also.

The only serious thing is that i'll have to order any parts i need from the USA - Its like trying to find rocking horse you-know-what over here.

[wtdash]

Replace the fluid 2-3 more times to ensure you get most of the old (stale?) stuff out.

Drive it for a few miles between changes.

Probably cheaper than any other remedy, @ this point.

Good luck
TD

[log1call]

Given that it's been sitting, I'd bear with it for a while and hope he heat and use frees up a valve or solenoid. If it doesnt, then the inevitable overhaul won't cost much extra from totally wearing out the clutches, which is what sounds like what is happening.

In the mean time you could change the fluid, checking that the filter is clean and that the old fluid doesn't smell acrid or like burnt clutch pack.

To do a proper diagnosis you need pressure gauges and to carry out the test procedures as per the manual. You can do some of the tests without the manual... change speeds, stall test. time test etc.

[brendan]

Ok - Update on this:

Thanks for all your help, i have found (through testing) a few things.

1. The surging was infact, massive boost cut. My MBC seems to be defective, so i'm turning that down to see if it solves things. (although when fully screwed OUT i'm still reading 1BAR boost, instead of the 0.6 im getting with the solenoid hooked up - Is 0.6Bar standard boost, or limp home?)

2. The misfire is NOT due to plugs or coils, as i've changed them all. and cleaned the MAF

3. No tranny error codes, or ECU codes being thrown up. (Although tranny has stored codes for Vehicle speed senors 1 & 2, probably defective when the box was changed)

4. TPS is throwing up wrong resistances but more worryingly - Zero volatge from one of the pins noted in the documentation supplied to me, i've traced the ECU pin and connector, no Voltage there either, so i have a broken wire somewhere between Loom & ECU.

5. Still feels like its binding, but infrequently - i'm guessing it still needs a good flush and lots of heat to free things off.

The TPS is my main concern, its not throwing a CEL, but its obviously beyond destroyed. lol When i trace the broken wire and get a new TPS i'll update again, but it seems that the ECU would not recognise WOT if it was buggered, leading to fuelling issues at the top end of the rev range.

Just for kicks, i'm also going to disconnect the KM/Miles convertor and put it back to KPH, incase it was installed badly (the wiring under the dash seems like its been done in a rush.

Anyway, any suggestions or additions to the above are welcome, thanks again for your help.

[Legacy777]

On the TPS, which pin do you not have the correct resistance and no voltage?

[brendan]

Hey dude,

It was my friends error in testing the ECU pins, i had a bash at it tonight and the voltage is correct, but the resistance on the pins was out by a fair bit.

I used the testing guide you posted for me on how to adjust the TPS, works a charm. Awesome info.

Tonight i did the following:

1. Added massive earth wire from battery to body - just incase old ones were shot.
2. Hooked up OEM boost solenoid and all vaccum hoses.
3. Roughy adjusted TPS so i was getting continuity as stated in instructions.
4. Re-set ECU

Took the car out for a blast, and its performing better, but not 100% still.
Gearchanges are lots better, and the misfire/fuel cut/whatever at 5K rpm+ is not as bad.
The over-revving has stopped (normal change points seem to have been resumed)

I'm thinking further adjustment of TPS is in order, but im hunting for a brand new unit as i'm sure its knackered.

I have Iridium plugs in right now, OEM spec with regard to temperature, but i think i may go for copper ones and gap them a bit smaller to see if it makes any difference.

All in all, a productive night (It's only 1045PM here right now).

Thanks again for the info, this i'll keep updating this thread each time i make progress, i'm thinking it could turn into a "Problems with a 4eat Legacy turbo - look here!" kind of thread. hehe.

Right. Bedtime.

Cheers
Brendan

[Legacy777]

Good to hear you made some progress Brendan.

Can you provide some more info as to which resistances were off of what they should be.

There will be some variation, but if they are way off, like you're thinking, you should probably try and find a different TPS.