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.
Avatar
Ihbigred
June 6, 2011.




Interesting that "advancing" the sensor caused the shifting flare to dissolve mostly. Makes me believe even more that it's a PCM issue being that we have been able to resolve the flare by "tricking" the computer of what really is occuring.
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Tiny
Ihbigred
Sep 10, 2012.
Well I agree it is a PCM issue, but what are the chances of getting THAT fixed, since apparently these computers are not reflashable? I program computers for a living, and I'd love to get my hands on the code for this computer, but again what are the chances? My car acted as if there were two separate computer events: one telling the transmission to disengage 2nd gear at about 2600 RPM, and the second telling it to engage 3rd at 3000 RPM, so the flare happened over the 400 RPM range from 2600 to 3000. Under harder but still moderate acceleration, the "disengage 2nd gear" event was delayed until 3000 RPM and there was no flare. So that gave the the idea (after several years!) To fake out the computer by tweaking the TPS to simulate harder acceleration. Strangely enough, it not only raised the RPM for "disengage 2nd" but seemed to lower the RPM for "engage 3rd". Bringing the two together made it all better.

I'm intrigued by the earlier poster who got good results by using a potentiometer to simulate lower resistance (higher coolant temperature) at the ECT sensor. A jumper between the two sensor leads, with the proper resistor, could (I think) change the resistance of the sensor circuit appropriately. Again, it's a way to fake out the computer, but it sounds like it could give cleaner results than the TPS adjustment. Guess I'll have to do some direct-current-physics research to find the proper resistor -- high school physics is pretty far behind me now, so I think it can be done but I don't remember the equations!

Tiny
Rberq
Sep 10, 2012.
Oops, sorry ihbigred, I see the "earlier poster" with the potentiometer was you. I had only skimmed the thread and I missed the problem about cold starts with the potentiometer installed. According to my shop manual, 150 ohms represents a very hot engine, coolant at 212 degrees or higher. Also since the ECT sensor does not respond straight-line to coolant temp, my simple idea of a parallel resistor in the circuit probably would not work -- I still have to think that through. 1/R = 1/R1 + 1/R2.

Tiny
Rberq
Sep 11, 2012.
Resistance in a parallel circuit = (R1)(R2)/R1+R2

Rivermikerat
Sep 11, 2012.
Rberq,

I'm glad someone else has gone to some steps to try and resolve this! Yes, sadly an in series or paralell resister would not resolve the problem due to cold starts, but! If someone was willing to do some circuitry they could create a cool little black box to change the resistance at operating temperature! I'm an engineer with some minor background in circuitry, but I am elbow deep in grease with my V10 automatic conversion to Cummins diesel w/ manual transmission : ) With this box someone could either post how to make it, or make some pocket change on the side. I got the same result seeing the engine was running "hot" by seeing the resistance to temperature curves for the cts sensors.

FourOur,

I went to the website and browsed a bit, but am not sure if you're suggesting we buy some diagnostic tools?

Tiny
Ihbigred
Sep 11, 2012.
FourOur is a spammer and he is history now.

KHLow2008
Sep 12, 2012.
It's sad that some people don't know how to make a good honest living.

Thanks for resolving that KHLow

Tiny
Ihbigred
Sep 12, 2012.
You're welcome.

KHLow2008
Sep 12, 2012.
I have the same issue. Anyone consider a worn out transmission? Your trans is slipping due to wear. Even a Honda wears out.

Tiny
427ZL1
Feb 13, 2013.
Thanks for the input and I had considered that, but if you will read through the entire thread you will read that we were able to remove the problem flair in two ways: 1. Trick the car into thinking it is running warmer than actual and, 2. Changing the ecm to a vtec model and doing the "minime" conversion. I've never personally seen a transmission that was worn out act like this. Maybe you can shed some light on which component is worn?

Tiny
Ihbigred
Feb 13, 2013.

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