F23a swap issues

Discussion in 'Engine & Transmission Mods' started by ABW, May 14, 2018.

  1. ABW

    ABW New Member

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    Through accumulated hours and hours of research I have failed to find a solution to my shifting problem. I have found many great threads in this forum, but I haven't found one that is particular to my situation. A couple months ago I swapped the jdm F23a motor and tranny into my 99 Accord, everything was a huge success except the way the tranny behaves. It only shifts at 3500 RPM. Accelerating soft in 1st gear won't shift untill 3500, more of a slam into 2nd than a shift. Accelerating hard in 1st will shift as soon as it hits 3500, shifting smoothly into 2nd. Getting off the highway it will downshift into 3rd at about 45mph, jumping the rpms up and here is where it gets interesting. There is a power lag for nearly 2 seconds like the torque converter has to catch up to speed. It pretty much does this every time it downshifts into any gear. Occasionally I get a code for the TPS. When I removed the engine the throttle cable snagged up and got streched (not attached to throttle body or tps) and I tried to use it but it threw the tps code. So I replaced the cable and had the code reset, but it will come back on for a few minutes every 12 hours of drive time or so and turn back off. Because it is the JDM variant F23a I had to use my usdm intake manifold, so the TPS is the one that was working properly for me before the swap. Let's visit more of that JDM to usdm conversion, I had read up online that the transmission sensors also need to be swapped. I did this in 3 stages to see what difference it made. In my case it made no difference. First i drove it with JDM sensors, then I swapped shift solenoids a b c and d then drove it. Then I swapped the rest of the sensors and drove it, no difference. No change in the shifting behavior. I should mention the atf I used is the same stuff I've flushed my previous transmission with that worked fine, which I believe is the Castrol import. I have been driving it daily, like I said, everything else performs great so one thing I realized is that I could pop it in and out of neutral to shift it while accelerating. That's how I've been driving it, so if anyone can give me some good advice that could lead to the solution I would greatly appreciate it. I documented the full swap with a lot of great pictures so I will post those soon. Thank you for your time.
     
  2. BlkCurrantKord

    BlkCurrantKord Super Moderator

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    Did you just swap the motor or motor & trans?
     
  3. ABW

    ABW New Member

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    Both the motor and tranny, the tranny was mated to the block when it was shipped to my house so I'm assuming they both are original and havent ever been separated.
     
  4. BlkCurrantKord

    BlkCurrantKord Super Moderator

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    Put the original trans back in if it's still good and I bet your problems will go away
     
  5. ABW

    ABW New Member

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    Actually the whole point of the swap was to replace my bad transmission, no reverse and major slipping, so that's not going to be any help unless I rebuild it. Plus I'm sure the solution is more simple than swapping another transmission. Especially if someone says the fix is to use only Honda atf, particularly in the jdm transmission. I'm halfway convinced that's what it is because it seems to be a hydrolic pressure issue and not electrical or mechanical, unless the 50k setup has a failed torque converter. Any other suggestions are welcomed
     
  6. Student005

    Student005 Active Member

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    It sounds to me like the tranny you got is shot. I did the same exact swap a few years ago and my tranny still shifts smooth-ish but I credit my transmissions longevity to Honda ATF before it’s too late I would, if I was in your shoes, give it a try. But these autos are a pain in the nutsack that’s why, after my trip this summer, I’m going to begin my swap to manual. But let us know what fixes it


    Sent from my iPhone using Tapatalk
     
  7. ABW

    ABW New Member

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    Issue resolved: my TPS was damaged when I installed the engine and I couldn't see the damage because it was on the back side of the sensor. So when I plugged the sensor back in the connector smashed one of the 3 terminals, which wasn't discovered untill I removed the throttle body to inspect the tps today. Now she drives better than ever and I'm very satisfied with my swap after I got through some minor set backs.
     

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