1998 Honda Civic Transmission Flare

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

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".

So I got a new TPS as you suggested. How much did you advance it where you noticed a significant improvement?

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.

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.

Vwjobber - do you have any update on the longevity of your fix? I'm going to make an attempt at a repair once it warms up a bit outside here and I'd be inclined to try your fix if it's still working for you. I am in disbelief that you have a 1998 with only 26k, makes me wonder if your problem is a bit different than mine (with 210k).

Rberq - thanks for the details, they are much appreciated. I'm working on this problem sssllllooowwwwly as you can tell but its still on my mind as the car still flares alot.

Sorry for being out so long. I didn't get notifications that there were replies to the thread.
I'm surprised that replacing the linear solenoid resolved the issue, because I purchased a new OEM Honda linear solenoid and it did not change the shifting flare.
I didn't try adjusting the TPS out of spec, all I did was verify it was in spec.

As far as replacing the ECM, I had considered doing that with a known good one, but it is like finding a needle in a hay stack to find a civic that doesn't have this flare and they will let you try it out first. Believe me, I tried. Then I didn't feel like spending a lot of money to buy one from Honda just to have it not work or fail eventually.

Ihbigred -

I'm not sure I adjusted the TPS out of spec, I just adjusted it to the extreme end of the specified range. It may be still in spec, or slightly out. But it's working, so I'm not going to mess with it. :)

Rberq-

Thanks for clarifying. If it works, use it

Finally got around to replacing the TPS and the Linear Solenoid (not at the same time). I tried the TPS first, advanced it slightly so the voltage was 0.62 closed and 4.62 open (spec is 0.5v and 4.5v). This did help some but mostly it just shifted the speed at which the flair/gear hunt (TCC problem) occurred from 40mph to around 30mph. Also the TPS that is stock on the vehicle is capable of being advanced - you don't need to buy a new one. I adjust the TPS back to spec (0.5v-4.5v) and replaced the Linear Solenoid. Replacing the solenoid does require draining the trans fluid. The old solenoid appeared corroded around the connector and slightly dirty in the metal mesh filter inside. After replacing with new OEM solenoid the problem seems to be fixed! Hope this helps somebody decide what to do with their vehicle.

Farmersride -

It's interesting that the mesh filter looked dirty on your linear solenoid. One of the service records I have for my car (from before I owned it) was that the dealer "cleaned transmission screen" at 60K miles. I have always assumed that was one of the solenoids, but never really knew.

I'm glad that the linear solenoid seems to have helped some resolve this! That makes life so much easier. We ended up cleaning the screen on one of my relatives Accord and it resolved the harsh shifting transmission on her vehicle. It's definitely a very common problem.