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F4A22 tranny issues

Not sure if this is the right section since it’s a DSM, but it’s a technical issue. Move it if need be.

So I had a pretty crappy weekend revolving around my 1993 Plymouth Laser RS (N/A w/ auto). Drove it to a show, and it drove fine. Went to leave, backed out of spot, put it in drive and it just free revved. Same for 2 and L. Park, reverse and neutral work fine, but all forward gears are out.

-RPMs don’t suggest any load being applied
-Fluid levels appear fine (though technically hard to say since it hasn’t actually been run through gears, but no signs of any leaks and I had checked it a couple days before and it was good)
-All sensors and connections looked good (didn’t have a multimeter or values to check against though)
-Shifter linkage and position sensor are set correctly

Unfortunately the FSM points to Rear clutch or One-way clutch. Seems odd that they would go out so suddenly though. I’m honestly hoping it’s the valve-body (N-D control valve or Rear clutch exhaust valve seem most plausible) since I have a spare and it can be done w/o pulling tranny.

Who here has experience with the autos (F4A22)? Have you had, or known someone that has had similar issues, and what the cause ended up being? Hopefully it’ll be back at my house today so that I have tools to work on it and properly diagnose. Any inputs would be greatly appreciated though.
 

Launch

Well-known member
end clutches, which really isnt hard to do. Make sure to soak the disks in mitsu ATF for a few hours atleast prior to install
 

Wizardawd

Well-known member
End clutches is 4th (OD) only. Even with totally shot end clutches you still have 1-3. The usual symptom of failing end clutches is a flaring going into OD (IE, rpms jump a bit before the gear actually engages).
When they totally fail it will shift fine from 1-3, then when it goes to shift into OD (4th) it acts like you just shifted into neutral. But, leaving the OD button off will still allow perfect 1-3 operation.

Wiz
 

End clutch is only OD. Already had the end clutch issue and it's already been done.

Appears I did find issue. Got home and started with electrical diagnosis. All resistances checked fine. Checked for fault codes and it just kept flashing half second on, half second off /ubbthreads/images/graemlins/confused.gif Pulled control unit and popped case open, small brown dot creaping from under the 47uf cap. Pulled it and theres a nice ring of acid. Cleaned it up and the traces look fine, only ate two solder holes. Going to replace and see if that was it or not.
 
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Bad news. Did some research and apparently the tranny normally defaults to 3rd in all forward drive gears with faulty/no TCU. Find out when I get home today I guess.
 

Hi. We need to talk. I have the exact same problem in my 1990 laser. Will go all day in reverse, but nothing forward. I rebuilt my tranny myself 2 years ago and dread the thought of having to haul it out again /ubbthreads/images/graemlins/banghead.gif. The three most probable things that could cause this problem are a blown piston seal in the rear clutch, Planetary Failure, or electronics. When I bombed out my tranny previously it was failure of my planetary gears. I remember there being a bunch of noise when I would try to put the car in gear as the planets would try to engange. There was also a lot of metal chips in the pan. The planetary gears in these trannys have a small undersized roller bearing behind them that burns up and then the planets die later. I dont think this is our current problem. Either a blown seal (in the middle of the tranny), or bad electronics. Hopefully your bad capacitor is your (and my) problem. I think I am going to pull mine out and take a look.
 

OK, I went out to my car and unpluged the solenoids and my car went forward /ubbthreads/images/graemlins/laugh.gif. The solenoid plug is the one near the dip stick. If you need help finding it, let me know and I can email you a picture. I am hoping that means the problem is electronic and that the there are no internal issues.
 

Terry Posten

Well-known member
I also clean and replace TCU caps. /ubbthreads/images/graemlins/hsugh.gif
 

Made the discovery myself by accident. Also glad its not the tranny, but also not sure its the TCU since I did the cap yesterday and there were no signs of damage from the leak.

-Replaced the TCU cap yesterday and reinstalled.
-Still same issue, so I drop the pan and swapped in a spare valvebody and solenoids I had laying around.
-It worked, but then I relized I also hadn't plugged in the solenoid pack. Plugged in then nothing.

Just going to leave it unplugged and in limp mode till I figure out whats up.

Also made the interesting discovery when I went to take it around the block that I lost my turn signals. Was getting dark so I only checked fuses 7 & 12, but I'll go through all my fuses today.
 

Here are a couple of interesting threads from DSM talk that you may find helpful.

1) Another guy with a bad capacitor. click I think the lesson here is that bad capacitors can screw with other stuff on a board, so dont give up if you replace a leaky capacitor and everything is the same. A new TCU may fix it.

2) here is a nice cross reference for TCU's if you decide you need to find another one. It seems to cover everything but the car I own:

click

Re: Compatible TCU's

These are TCU part #s

MD738998 91-92 FWD, 1.8L
MD750092- 90-92 AWD
MD750093 91-92 FWD, w/turbo
MD750525 91-92 FWD, 2.0L, w/o turbo
MD754075 93-94 FWD, w/turbo
MD754076 93-94 AWD
MD754077 93 FWD, 1.8L
MD754079 93 FWD, 2.0L, w/o turbo
MD756600 95 FWD, w/turbo
MD756601 95 AWD
MD756916 94 FWD, 1.8L
MD756917 94 FWD, 2.0L, w/o turbo
MD759736 96 FWD, 2.0L, w/turbo
MD759737 96 AWD
MD762042 97-99 FWD, 2.0L, w/turbo
MD762043 97-99 AWD
MR483685 97-99 FWD, 2.0L, w/turbo
MR483686 97-99 AWD
 

Thats a good list to know. I'm aware of the ability of the caps to damage other things on the board, but thought I was in the clear. Acid never got further then the corner on the caps pad and didn't damage the traces or touch any other components. Also took the old cap into work once it was removed and checked it on our cap analyzer. Measured 46.6uF and the ESR wasn't to far out of spec, so didn't think it could've caused to much electrical havoc.

So what exactly are the cross compatibilities? From what I got pre-93' were 3 plugs and 93' and later are 2. Shift points vary by model as may the eco/power switch, but they're somewhat interchangable.

Will a 95' one work in my 93'? Ask only because there are a bunch of 90-92 and 95 at the local pull-a-part that all had autos, but no 93-94.

I can look to see what they have and pull one for you if you want. Whats the model number on yours since you said its not on the list?
 

misterfixit

Well-known member
another thing to try is bell out the solenoids. if the coils go out they will give up. in '94 mitsu bput out a s/b on replacing the solenoids on the valve block. pull the connector and run a meter to check they all have continuity. if one works and some others don't the ebox will be stuck in a strange mode.

i've also killed a fwd clutch on these before wit a similar effect.

Rich
 

The interesting thing is my 90 only has two plugs. I have read some places that two plugs are for FWD and three plugs are for AWD. Yes I am a bit confused on what cross references too. Anyway, I pulled my computer out and it looks flawless inside. No Capacitor leaking, bulging, corrosion, or anything. Of course with electronics looks dont meant anything. My computer number is MD731302. What is your computer number?
 

I had checked the solenoids resistance on the old valvebody when I first started having the issue and they checked fine. Can't remember what my number is on mine. might go check during lunch.
 

misterfixit

Well-known member
i'll scan the s/b and upload. will be tomorow now though.

rich
 

Ok Here is another thing to try. The A and B solenoids are the ones that shift your car. I took a cigarette lighter power plug and connected the hot connection to a wire I then connected this hot wire to a switch and then to the terminal for solenoid A with an alligator clip. I then connected a second wire and switch and I did the same thing for Solenoid B. Once you hook this up you should be able to shift the car as follows

From a post by crackeddsm on DSM Talk the shift sequence would be:

Solenoid A (switch 1) on, and Solenoid B (switch 2) on would be First gear.
Solenoid A off, Solenoid B on would be Second
Solenoid A & B off would be Third
Solenoid A on and Solenoid B off would be OD/Fourth.

Which matches what I see in my factory manual?

Anyway, I installed this in my car and unfortunately first and second still do not work. I was able to shift between third and forth (OD) with no problems. You should give this a try. If it works for all your gears then all you need is a computer. If it doesn’t, then you probably have a solenoid problem or blown rear clutch seal. Or another solenoid needs to be turned on to make the tranny shift in first or second, but I don’t think this is a case. If you give it a try, let me know how it goes.
 

misterfixit

Well-known member
aren't there 3 solenoids? theres the Pressure control solenoid valve. i'll grab the pics i have of the valve block when i scan the S/b
 

There are actually 4 Solenoids. The Pressure Control solenoid valve (PCSV), the shift-control solenoid valve A (SCSV-A), the shift-control solenoid valve B (SCSV-B), and the Damper clutch control solenoid(DCCSV). The Pressure control valve is only on in first gear. The damper clutch control valve is on in 2nd, 3rd, and 4th gears. I dont think that the PCSV or the DCCSV control valves control shifting between gears, but I would love to be wrong on that! Looking forward to seeing the scanned SB. In the mean time for my car I am concentrating on looking at the SCSV-B /ubbthreads/images/graemlins/crazy.gif or the rear clutch piston seal /ubbthreads/images/graemlins/banghead.gif. I really hope our problems are something electrical.
 
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