Mechanics

TRANSMISSION FLARE

1998 Honda Civic • 4 cylinder FWD Automatic • 164,000 miles

I have a 1998 Honda Civic DX with automatic transmission. When I purchased the car it had a shifting flare from 2nd to 3rd gear. The flare wouldn't occur until the transmission had warmed up by driving and then would persist. The one exception was that with a soft exceleration it would flare, but a hard acceleration it wouldn't flare.
Later I discovered that after some trips of about 75 miles or longer the transmission wouldn't flare anymore no matter how I drove it until after I shut the car off and turned it back on then it returned to flaring again.
I recently changed the transmission fluid and checked all the transmission solenoids for resistances within Honda specs and all activate when energized manually.
The car within the last week had gotten warm while driving so after letting it cool down I replaced the thermostat and bled the system of air.
Now the car's temperature guage fluctuates from normal to hot opperating conditions occaisionally and when it is fluctuating the shifting flare is non existent and when the temperature guage remains at normal position the shifting flare occurs between 2nd and 3rd. Also the left blinker started acting up (first it blinked like a bulb was burnt, then it worked fine, then blinked very slowly and is back to working properly) at the same time that the coolant temperature did. The check engine light is also not on.
The cooling fan works properly and when shorted so fan operates manually it will not cool the coolant temp as indicated by the temperature guage on the cluster.
I took the car to a transmission shop and after investigating it they guessed that one of the "pressure switches" were bad (assuming they were referring to the solenoids). I didn't have them do any further work to the vehicle after that.
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Ihbigred
June 6, 2011.




Yes, you should flush after trying it.
What I'm thinking is that parts expand when they heat up. So, there may be leaks while everything is cold that either get smaller or go away completely when everything gets properly warmed up.
Electronic parts sometimes tend to fail when cold and work somewhat properly when warmed up.


Rivermikerat
Jul 11, 2011.
I'll give it a whirl, but the catch with your suggestion being that (reference begining of thread) the car shifts perfectly fine when it's been sitting for a while and if it's been cold out and gradually, after one or two shifts from 2nd to 3rd, starts acting up. So when cold or sitting for about an hour, it's okay. Also when the engine temp reads above normal, it's okay.


Tiny
Ihbigred
Jul 12, 2011.
Yeah, I read right past that part. Have you ever used a cooling system thermometer to see how hot the coolant really was when the gauge was reading high? With the way you describe the problem, I'd first start and rule out anything electrical before anything else.

Most temperature sensing units are resistors that are adjusted by heat, so when the sensor sees an extreme in temperature one way or the other, the resistance of the sensor will change to an extreme value, either high or low.


Rivermikerat
Jul 12, 2011.
Actually no I didn't. Since it was a bad head gasket, I assumed it was an air pocket that was being sensed. This car in particular has three sensors for the coolant. One that runs to the dash guage, another to the ECM and one for the cooling fan. I have not been able to follow any schematics that show a direct correlation between the temp sensor for the ECM and the transmission.


Tiny
Ihbigred
Jul 12, 2011.
If the ECM is modifying the voltage it sends to the transmission based upon the voltage/current received from the temperature sending unit, it may be sending too much or not enough voltage.


Rivermikerat
Jul 12, 2011.
From what you described above I did some more quick troubleshooting. I disconnected the TCS and the car would shift fine from 2nd to 3rd every time with the exception that it wouldn't shift into fourth. Once I reconnected the TCS the car began to "flare" from 2nd to 3rd and it would allow the car to shift to 4th gear. I then decided to swap the TCS for another one from my other civic and the problem continued. Because of this I'm wondering if the ECM is bad?


Tiny
Ihbigred
Jul 21, 2011.
Without looking at it myself, that's what I would say, also. It doesn't seem to be a ground loop issue, since all grounds are in great shape. "Unless doing a hard acceleration". THAT tells me that there is an outside chance it's the valvebody. Which, as far as I know (not being a transmission tech), requires swapping valve bodies to verify.


Rivermikerat
Jul 21, 2011.
You might also check with honda to see if any pcm reflashes(updates) are available or needed.


Merlin2021
Jul 21, 2011.
I went ahead and put another ECM in the car that I got with a car I purchased that had 140k on it. The purchased car also has the same issue and it has been converted over to a VTEC from Non-VTEC using the VTEC ECM. My personal car still had issues with the shifting after swaping ECMs. The next thing I'm going to do is replace the A & B shift solenoid pack to see if that resolves issues.


Tiny
Ihbigred
Sep 20, 2011.
Let us know how that goes. I'm still thinking that it may be a valve body issue.
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Rivermikerat
Sep 20, 2011.

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