I have a 1996 Acura 2.5 TL with 130K miles original owner so still good condition overall but in past 3 months I've been experiencing intermittent issues with hard idle surging after engine warms up. Then after driving for a bit, the transmission would not want to shift smoothly, and rpm would rocket up before experiencing hard shifting. It wasn't every time but gradually worsened to every time you start it up in the past week. I've been reading up on here and googled around the past month and thought it was my IACV or Fast idle valve so ordered refurbished units and replaced both just to find problem still persisted. Next checked all vacuum lines and they were still good. Cleaned throttle body, checked EGR, PCV, distributor&wires, spark plugs, etc to no avail. I even flushed tranny and changed out tranny filter to try to remove tranny hard shifting from the equation. Then I saw one thread mentioning a leaking capacitor.

I couldn't find any refurbished ECU under $200 and didn't want to chance acquiring a used ECU from salvage yard. I decided to remove my ECU and check if a capacitor was bad or not. It was easy to remove once I found where it was located as I thought it was under the radio like newer cars but luckily found diagram showing under carpet on passenger foot area.

ECU diagram

Never opened up an ECU before so included some pictures of the unit.

ECU unit

Front side of ECU board

Rear side of ECU board
You can clearly see that one of the larger Capacitor was leaking onto the board. Luckily, the board wasn't damaged too much as I was able to use alcohol to clean up the leak area okay.

Leaking capacitor
I couldn't find an exact match for the Nicochin capacitor so went with UPJ1J470MPD from Mouser with same 63V, 47uF, 105degC ratings.



De-soldered bad capacitor and cleaned up board some more to remove excess solder and used heat resistant tape to tape over traces to prevent further damage if new capacitor were to ever leak. Had to remember the negative side (white stripe) needed to match up to the negative sign on the board before soldering new replacement capacitor. Reinstalled repaired ECU, hooked up wires and fired up the engine crossing my fingers that it would fix it. Engine warmed up and then idled low as usual with no more surging. Let it run for 10mins before taking for test drive. No more hard shifting from transmission and it now shifts at usual lower RPMs. All is well now so saved me money from taking into shop to have it diagnosed with costly bill.

Fairly easy to do if you know how to use a soldering iron. Hardest part was finding a source for the capacitor as shipping was $8 for a $0.49 capacitor.

 

interesting bc ive been going through this myself and im on here looking into it. thanks for the insight

 

I know I wasted so much time troubleshooting and money changing out other parts. The car is still running fine the past 2 months post the fix. Also, gas mileage has improved since then which helps with the higher gasoline prices. Good luck on your attempt to fix.