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.




Hi Ihbigred,

I"m going to bring this thread back to life by adding that I have a 2000 honda CRV which is developing this same problem. I honestly cant recall how long ago it started. The thermostat was stuck open and the engine was running very cold for the last few months and I almost forgot about the issue. I just replaced the thermostat and the flare is back worse than ever. Only happens between 2-3 gears and only with light throttle application. Only happens when engine is at normal operating temperature. I've got 199,000 miles on this car and I'd like to keep it going.

If I may ask why didn't you try just replacing the PCM if you suspect that is the cause? I am an electrical engineer by trade but I don't know much about fixing cars.

Chris

Tiny
Farmersride
Feb 2, 2014.
When I said the PCM was the problem, I didn't mean my individual PCM was defective. I meant ALL of them are defective due to bad programming logic, which can't be fixed because the PCM is not re-flashable. In fact several of us, me included, did try swapping out the PCM, with no benefit. My problem was fixed by adjusting the Throttle Position Sensor to be slightly out of spec. Another user found that simulating a different engine temperature fixed the problem. Why? Ha! That is the question! For myself, with a 16-year-old car at 285,000 miles, fixing it via the TPS adjustment is enough to keep me happy even though I know it is not "right".

Tiny
Rberq
Feb 3, 2014.
So I got a new TPS as you suggested. How much did you advance it where you noticed a significant improvement?

Tiny
Farmersride
Feb 5, 2014.
How much did I advance the TPS? I used some white-out (just because that's what I had on hand) to "scribe" a line across the TPS and the throttle body so I could get back to the starting point if need be. White-out goes on with a small brush, so it was a fairly wide scribe line, not narrow like a sharp pencil would make. Then I advanced it perhaps twice the width of the line. I found the shift points occurred at significantly higher RPM, and were harsher shifts, but no flare. Then I backed off a little at a time, driving it a day or two for each adjustment, until the shifts were more reasonable and not harsh. I wound up with pretty normal shifts, and just the hint of flare once in a while under very gentle acceleration.

If you retard the TPS too much it will turn on the check-engine light. If you advance it too much, It might also turn on the CEL -- I don't know, it happened to me only when retarding.

When my car is started cold, it stays at a fast idle longer than it should even after warmed up, though it eventually drops to a proper idle. I don't KNOW that that is caused by the out-of-spec TPS, or whether I have some other problem. I suspect the TPS, but when restarted warm it is fine, so when it annoys me I just shut it off for a second and restart. Usually I do the restart while driving along at 30 or 40 MPH -- just leave it in gear, switch off the ignition and switch it back on, and it restarts without cranking the starter.

Good luck trying your new TPS. Please report back whether it helps you or not, and whether you experience any fast-idle problems.
AD

Tiny
Rberq
Feb 5, 2014.
I read this thread several times over in an attempt to figure out a solution to my problem. I recently purchased a low-mileage 98 civic EX from a friend who was no longer willing to spend any money or time on it. The car (amazingly) had only 26k miles on it.

The transmission (B4RA) exhibited the same symptoms as frequently described on the web: shift flare of approx. 500RPM between 2nd and 3rd gear. The lower the acceleration the harder it flares. Other gears work okay, no fault codes, doesn't do it when engine is cold, or when accelerating very hard.

I flushed the ATF and replaced it with new Honda fluid, which had no effect. However I could inspect the magnetic drain plug, which had a lot of fuzz but no chips. I assume that this is due to normal wear of the friction parts and perhaps accelerated wear of the 3rd gear clutch due to the flaring.

I figured that the linear solenoid was the most likely culprit as this device isn't ON/OFF, but rather a pressure modulator. It would explain why the tranmission does not exhibit all the symptoms listed in the factory manual that point to item #19. I purchased a genuine Honda part 28250-P4R-315 ($150) and replaced it. The shifting problem disappeared!

I also read somewhere that others report this solution worked but did not last long. I will post again here only if the problem comes back. I am assuming that this linear valve design is not tolerant to very fine debris that are created by normal wear and may benefit from regular ATF change and drain plug magnet cleaning. Perhaps there is a link to the state of the internal transmission filter, which is not exactly inspectable. Otherwise the linear solenoid may require "periodic" replacement if the transmission (as it sounds) produces too much fine debris by design.

Best regards to all.

Tiny
Vwjobber
Jun 29, 2014.

AD