got a 1990 mazda rx7 GXL Automatic it only shifts gears if i let go of the gas pedal or if i am going down hill and not pressing gas pedal itstarts switshing gears ,if someone came across this problem before

 

ok seeing as I am qualified to answer this (I'm a master transmission rebuilder) I'll give you a few things to look at on the JATCO N4AEL:

1) Check vacuum to the modulator this SHOULDN'T affect the shift timing but it may if there is no vcauum present also the modulator has been known to get stuck by the diaphram getting hard or the spring inside rust and break. If you replace it make sure you get the correct one there are turbo and N/A versions there are also screw-in and bolt-in models and they can't be interchanged. If you replace it and get a new modulator the new modulator isn't always the same physical shape as the orignal (usually the orignal is a large body and the replacement are small body.

2) perform a self diagnostic on the TCM to see if there are any sensors that have failed such as: vehicle speed sensor, throttle position sensor or shift solenoids. This is the best place to start but you must have the proper tools to do this. I suggest taking it to a shop that can do this it will save alot of time over checking individual sensors and 'noids.

Here are some of the specifications for the trans controller inputs:

kickdown switch under dash on throttle pedel bracket: Idle to 7/8 throttle less than 1.5v 7/8-full throttle 12v

solenoids: 13-17 ohms to ground

vacuum switch: 16.1 - 17.3in Hg. switch should show open less vacuum than that should be closed

turbine speed sensor: about 245 ohms

vehicle speed sensor: Disconnect speedo cabe from transmission, check at the TCM should show 7v 4 times per revolution of the cable.

all these tests can be done from the TCU (Transmission Control Unit) I'll try to get a pinout of the connector for you.

 

Also I forgot to mention the inhibitor switch there is a possibility that the wron pan bolt was installed the the wrong hole (1 bolt is shorter then the rest) and the bolt can damage the inhibitor switch or the switch itself may be bad. I have the connector view I'll try to attach too.

 

hey thanks for your reply, today i took it to the shop they put in new vacuum modulator and a new trottle position snsor but still didnt help, they scan it for codes and all they came up with was oxygen sensor bad, and main computer, ohh yea i forgot to mension the hold light is coming on everytime i drive,do you have any ideas?

 

Honestly, just do a manual conversion. It's not worth the time and effort to fix an automatic. If you can, do a TII swap while you're at it (depending on how easy you can get the parts and such).

 

was the hold button checked for porper operation? some mazda's will not shift if the hold button is shorted also did they check just the ECM or did they check the TCU also they are seperate controllers and you have to check each seperatly.

 

im not sure if they checked any of them all they told me was that computer not putting out a signal to the throttle position sensor,i thought it might be a transmission computer the ECAT faulty what you think, i got a another computer tomorrow ill put it in see if they were right, but more likely its like you said something with the hold switch.

 

Check your fluid. I had the same problem. IF your fluid is bad and your clutch discs are burnt up they might be slipping or not letting it engage. If your fluid is muddy and dark then kiss that tranny goodbye. If you need a working AT computer I got one laying around. By the way how many miles are on it and whens the last time it was serviced? Was it power flushed?

 

hey thanks for the reply it was serviced yesterday and the mechanics said everything was fine,the car has 94,000 original miles,about that computer i really need it can you put it on ebay.

 

Now did they power flush it or just drop the pan and change the filter? If you need that AT computer PM me. Its a working unit. Still in my car. (minus the auto trans)

 

it could be the TCU but it could just a easly be any of the electrical components if you were in my area I'd check it for you and thell you eaxctaly what it is but it's hard to do from the extreme other side of the country.

 

naw i dont think they powerflushed it but the fluid was good when they took a look at it , you think it could be because of that?,

 

numan2 this what i found ou t the hold light is coming on when it going about 30 miles and it doesent stay on it just blinks and then goes away, say if it was the hold switch would that cause it, how can i check,ohh yea what does TCU stand for?

 

Hmm. My hold light blinked after I did my swap and left the AT computer still plugged in. When I unplugged the AT comp it stopped. IF the fluid looked good and it was flushed then its not a mechanical problem. If its flashing it could be possible there is a bad connection. There are like 5 or 6 wires that plug into the AT transmission. If you could inspect the harness and make sure they are all connected then maybe it will wind down to the AT ecu. Its all electronic unfortunately. I had a '89 GXL automatic. I did a 5 speed swap and still have AT **** leftover in case you need anything. A 5 speed swap is highly recomended. If you aren't concerned about performance then don't worry about it. I got a nice increase in rwhp and cut 2.6 seconds of my 1/4 mile.

 

alright thanks, i unplugged the transmission computer ans switshed the main computer now the hold lights is not coming on anymore but the car still wont shift i am going to try looking for those wires you were taking about.

 

are these transmissions governed by vacuum only? i thought they had a TV cable, if they do that would be the FIRST place i would check for a no upshift concern, well after checking the fluid level that is.

 

they are by vacuum but i didnt see no tv cable