hello men:



i am having problems with my car: 1991 accord DX, 2.2 ltr., auto. trans. money is tight so i hope to fix it myself. i have significant experience working on family members' cars.

here goes nothin', the problem began more than a year ago. the S light on the dash is on continuously and i can only engage first and third gears on the transmission. with the gear selector in 1 i can use first gear. with the transmission in all other forward gears (2, D3, D4) the transmission engages 3rd gear only. Reverse gear works fine.

i did some reading online and removed the ATCU (Automatic Transmission Control Unit) from under the floor carpet. i opened up the case and found a burnt spot on the printed circuit board.

i replaced the ATCU with one from the salvage yard. the ATCU model number was an exact match. i started up the engine and immediately the second ATCU melted. i could smell the stink in the passenger compartment. i pulled the ATCU and once again i found a burnt spot on this ATCU. i had opened the case before installing it and the circuit board had been pristene. now, i suspected the ATCU wasn't the problem but, some other component was faulty and causing the ATCUs to burn up.

an online friend suggested replacing the the A.T. Solenoid Valves (Shift Control and Lock Up Control) before putting another ATCU on the car. i bought a set of valves at the salvage yard along with another ATCU.

i started the car and the ATCU didn't burn up. the car ran well for months. then the old problem returned: S light coming on/staying on and only 1st and 3rd gears engaging. the ATCU no longer burned up. (i am not sure why this is.)

on-line i learned how to clean the solenoid valves. at first i used an awl to hold down the pintle inside each valve while spraying carburetor cleaner into the valve. then i learned to apply battery voltage to the valve during the spraying.

i own two sets of solenoid valves currently (each set includes both Shift and Lock Up valves). i've cleaned them well yet i get the same problem with both sets installed: S light on continuously and trans. only accessing 1st and 3rd gears.

it isn't feasible for me to continue driving the car using only 1st and 3rd gears. i have highway driving i need to do soon and the trans. must engage 4th gear.

a second problem exists. i wonder if it has anything to do with the first problem above.

occasionally when the engine is cold and the trans. is in Neutral (maybe in Park also) the idle will drop from about 2000 rpm to 1500 rpm then go back up to 2000 rpm. it can do this for a few seconds or a half minute, fluctuating up and down. then it settles and idles well. on an occasion or two the idle dropped so low the engine almost died. when i put the car in 1st gear it idles well.

returning to the first problem, on-line i read that the Shift Control Solenoid Valve may be the real cause not the Lock Up Valve. i learned of two tests to run to identify a proper working Shift Valve: a resistance test and a voltage test.

i then went to the salvage yard and checked a couple dozen Shift Control Valves. all failed the resistance test. the valves need have a resistance between 12 and 24 ohms. all the valves i tested came in at about 30 ohms. the Shift Control Valves i currently both fail the resistance test also.

my questions: are the two problems related? and, how can i repair the problems?

as i stated before i am disabled and money is tight thus, i hope to fix the problems myself. the current book value on this car is about $1100-. i don't wanna invest much into this car.

i wanna mention that at numerous times over the past months i checked the trans. for any stored trouble codes. each time i placed a jumper wire in the diagnostic connector under the dash no codes came up at all. this diagnostic feature isn't working on my car for some reason.

that is all i have for now. thanks so much for your help.



bec

 

On the 91 TCU, there should be a window with a led. If you jump that connector, does the light physically on the TCU flash?

 

hi:



thanks for your help.

the ATCU on my car has no led on it's body. i have seen some at the salvage yard that did have an led on them but, not mine.

according to my Haynes repair manual i am to read trouble codes from a light flashing on my dash once i add the jumper wire to the diagnostic connector. but, when i do so no light illuminates on my dash. one never has. this diagnostic system is not working on my car for some reason.



bec

 

What is the part number on the TCU?

 

hi PA:



hmmm, you got me there. i'll have to pull back the carpet, unbolt the ATCU and check. i don't think i recorded the part number anywhere. i'll do this as soon as i can. thanks,



bec

 

hello again PA:



how do i list "1991 Honda Accord AT" at the bottom of my messages? i recall a man suggesting it at this site. thanks,



bec

 

Under your User CP you should be able to add a signature. I think that you have to check something to enable it as well. It has been a long time since I first had to set that up.

 

hi PA:



as i said before, the TCU in my car currently is not the original. i believe this TCU is the same model as the original but, i am not sure. it has been some time since i replaced the TCU. i read this off the body of the TCU last night:


"AT Control Unit
28100-PXO-822-M1
3LX
Lot No. OX3OU"


i recall reading online that some of the original TCUs on these cars were defective. do you know if this is true? if it is, how can i learn if the TCUs i have are defective.

i have a spare TCU in my toolbox. the model number on the spare is not identical to the one in my car now but, it is close. it came out of a 1990 or 1992 Accord LX i recall.

thanks for your help PA. bye,



bec

 

Is your car a EX, DX, or LX?

 

hello PA:



i thought i listed that. i guess i didn't. my 1991 Accord is a DX sedan with an auto transmission.



bec