Calderfh

Hi everyone, my 1991 4runner 3VZE with an A340H automatic transmission has developed a bad problem with first gear. Today I drove it about 70 miles with no issue until I stopped at my mailbox on the way home, at the foot of a steep hill. When I put it back in Drive and started up the hill, I immediately noticed a substantial lack of power. I was able to make it home, about a half-mile. Later, I went to work, mostly downhill, but could still tell that first gear lacked power after coming to a complete stop. However, once I was going fast enough, the higher gears seem to be functioning as normal. Reverse is also not affected, it's as strong as it ever was. Upon returning to the mailbox area at the foot of the hill, I was not able to climb the hill to my house, and had to reverse the whole way back. I drained the ATF, it was very brown and smelled horrible. I added 4.8 quarts back in the filler tube and fired it up, but the problem persists. I don't have the materials needed to pull the pan and clean the filter right now, but I will tomorrow. Shift linkage seems to be working, at least as far as I can tell from the outside of the transmission. One thing is that the linkage does'nt look as pictured in my Haynes manual, and the shift lever itself has always felt pretty loose and moves side to side a bit. Any ideas on what could be causing this problem?

az4x4runner

Sounds like the transmission may not be starting in 1st gear, but rather in 3rd (direct drive). This is the A340H "limp mode" when there is an issue with a shift solenoid or VSS. Is your O/D light flashing? Try pulling codes and post back here.

Calderfh

Ah, that makes sense. No "O/D OFF" light flashing. Should I test the same way as check engine light? I read somewhere it's different for trans issues.

az4x4runner

Test the same way that you checked for CEL codes. Make sure O/D is turned on (so the light is off). Jumper TE1 and E1 and turn the ignition to "ON". The "O/D OFF" light will blink codes in a similar sequence as the CEL.

Calderfh

So, I pulled codes 12: knock control sensor signal, 25: air-fuel ratio lean, and 71: EGR system.ive had these codes for at least a month, but this time when I checked them, the "O/D OFF" light was blinking rapidly, no breaks between blinks.

az4x4runner

What happens with your engine RPM when you experience this loss of power during acceleration?

Is it real low like the engine is under a heavy load or is it revving like you're in neutral?

az4x4runner

Here is the A340H troubleshooting section from the FSM. Check out the flow charts for your symptoms.

Page AT2–26 has information on checking the manual linkage and the throttle cable.

Calderfh

Today I tested voltage at terminals S1, S2, SL and S4 and applied battery power to them as well. I got solenoid clicks at all except S1. So, I scored 6 quarts of ATF, and new trans filter, and rubber gasket today, and have 3 solenoids coming in tomorrow, although it sounds like there are 2 "shift solenoids" and one "lock up solenoid" easily accessible from the trans oil pan, and an additional "shift solenoid" in the transfer case. Should I replace S1 and S2, or just S1? They were not cheap, $135 each, ATP brand at NAPA, so if I can return one, that'd be great. Also, last time I cleaned the filter and put the pan back on, I used FIPG, and it worked great, just wondering if I can expect the rubber gasket to work as effectively, I know the engine oil pan gaskets are notorious for failing.

az4x4runner

That is a perfect test. I've had the A340H throw codes, or not, intermittently, with failing solenoids.

I replace all three when I have the pan down, but I don't like worrying about having to open it back up in the near future. RTV or FIPG is the way to go. I use Permatex The Right Stuff, it requires very little time before putting the vehicle back in service.

Calderfh

Replace S1, S2 and SL? Or S1, S2, and S4? S4 is in the transfer case, right? Ya, I used The Right Stuff on my engine oil pan, worked great.

az4x4runner

I wouldn't worry about the no. 4 solenoid in the transfer case right now. Even if it did fail in the near future, it is in a separate valve body, under a different pan. I've never replaced that one on my own truck's A340H with 244000 miles on it.

Also S4 is only turned on in 4 low as far as I know.

Calderfh

Sounds like I need a lock up solenoid too, then.

az4x4runner

Replacing SL as well could be added peace of mind. It sees less action than S1 and S2 do most likely since it just controls the torque converter clutch, depending on your driving conditions, but if you can afford it at the time I'd do S1, S2 and SL since they are all under the main trans pan in the same valve body.

Calderfh

Well, today I pulled the pan, cleaned it up real nice, replaced S1 and S2, installed a new filter and buttoned it all back up... to find that my problem persists. I did the manual shift test (which I should have done yesterday) and found that my problem is most likely mechanical. I tested resistance on the two solenoids I pulled out, 13.6 ohm on both. FML. Like I said, reverse still works fine, but like damn near zero power to the wheels in D, 2, and L. Same story in 4H and 4L. Is my trans toast or what?

89934runr

Was that code 12 or 52? Code 12 is for the RPM signal to the ECM (no G or NE signal, distributor to ECM). Much different issue than a code 52. This code also involves the STA (start) circuit signal to the ECM.

A knock sensor code (52) will pull power out of the engine until the issue is resolved. I'm not exactly sure what you're 'low power' feel is, but I just had a customer's '92 that needed the KS replaced, and what a huge difference it made once resolved. Customer's truck had the CEL bulb removed by a previous mechanic (to hide the code 52), so customer thought that was the normal power level. We fixed both, and he now loves us

Your lean code 25 will also kill power, so do some looking there. Split or cracked intake tube, loose hoses, old hoses, etc. The same '92 mentioned above had very slight air leaks at the injector seals. Remember, your engine needs an airtight path all the way from your VAF (where the ECM measures airflow) to the cylinder. I'd do a smoke test / air leak test as part of checking your issues.

Think about this- you have a knock sensor code, a lean code, and an EGR code. There is a possibility that they are all related. Most likely the KS / circuit has failed, and you have an air leak issue

IRT your trans- If it's not throwing codes, and not slipping, then it's time to focus your efforts elsewhere.