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This is a 95 Acura Integra GSR 5 speed P72 ECU. When I install it in my car I find that it is running the engine lean for the first few minutes (as indicated by an installed wide band oxygen sensor as well as an exhaust note change). After running for a few minutes, it richens back up to normal air fuel ratio and appears to run the engine normally as one would expect. If however you cycle the key, it goes lean again for a few minutes before richening back up to normal. This occurs every time the key is cycled whether it is warmed up or not.

I would like to know if this is a typical fault in a given circuit, and if it is readily repairable. I have added a ziff socket to the board and had previously been running the car using an emulator (Moates/Crome). I also installed a switch so I can toggle the jumper that switches the ECU back and fourth between stock ECU and emulator (I run stock, haven't ran Crome in quite some time). The lean condition occurs in either mode, so I am rather convinced that it is a hardware related issue. Anyway I would like to run this by the hive and get their input. Please advise.

Thank You,
RC Jaquette
503-302-8084 Cell/Text

at first startup the ECU is in open loop using the maps. (with the jumper removed its from the MCU, jumpered it's from the chip/emulator)
After the engine warms up or runs for a few minutes the ECU goes into closed loop, using the O2 to adjust the A/F ratio.

If it's lean during startup, then the maps that it's using are incorrect for the engine.

Since this is a P72 and you're running a relatively stock GSR then the maps it's using should be right.
Check your IAT and ECT readings. If they are reading incorrectly it will change the amount of fuel injected.

Also double check your switch, it may not be working correctly. (which may account for the no change in operation)

I had rather ruled out anything in the engine bay as being at issue as I am currently running a JDM P30 ECU and this problem does not happen with it installed.

I don't know if this is the case but I figure I may have damaged the P72 (USDM BTW) when I was testing my DIY-WBO2 (the building of which is what originally brought me to this site). The battery didn't quite have enough juice to fire up the WBO2 so I connected my battery charger to the battery and at one point turned the key on (IGN on/ENG off).

Like I said I have no idea if it harmed the ECU (I don't know why it would, its not like the charger generates crazy output) but it is the only thing out of the norm that I could surmise knowing the ECU worked fine before the engine rebuild and had this issue after getting it all put back together. I picked up the JDM P30 as a result and it was and has been plug and play.

The P30 is starting to give me issues and I would like to get the P72 back up. It could be my imagination but it seemed the car just pulled harder with the P72 (I am running a Sk2 ITR style IM, so its not about the IAB's) not to mention it is the one that has the Moates stuff installed and allows me to run Chrome. I suppose it doesn't make much difference as I ran it in stock mode all the time anyway as the car just runs better as a daily driver that way, particularly here in TX in the summer while running the AC. My Chrome tunes run great WOT....100 degree plus heat and AC cranking, not so much. Even with that being the case, I don't want to just toss it aside as I have a bit of money tied up in it and with the P30 starting to go wonky I'd like to get it back up and functioning normally if I can. Replacement P72's aren't cheap and having the option to run on a tune when I get the wild hair would be nice as well.

As a side note, not to get drug down a new rabbit hole. The P30 started giving a false knock sensor 23 CEL last year. The wiring all tests good according to the manual and I have replaced the sensor but still get the CEL after engine temp gets up to 1/4 on the gauge. The manual indicates the next step is ECU replacement. I have just been living with the CEL as the car runs just fine. More recently I am now also getting a 21 CEL (VTEC Solenoid) right at engine start, even though the car goes into VTEC just fine. The bits on this car are getting old and I figure the ECU may just starting to go south on me. This car has been my daily driver since 1999 and the chassis has over 600K miles on it. 5th iteration of motor and 3rd transmission.

This is the reason for the renewed interest in getting the P72 back up. If I have to spend time/money on a properly functioning ECU I figure the P72 is the one that has the most investment. Maybe the easiest thing to do is just put a switch on the CEL light circuit so I can turn off the annoying CEL light until I want to check for future codes as the car actually runs just fine in all regards with the P30.

I also don't want to throw money down a hole sending this P72 off to a repair joint if it is not likely that they can actually fix it. I figure if any place can give me a clue and or some pointers about how to move forward with this business it is here on the forums at PGMFI.....full circle where my tuning journey began.

ETA: With the P30 I am running an APEXI VAFC and a HKS Defencer (Crazy Jap spelling) it is the gizmo that defeats the P30 stock speed limiter. Don't know if it has any bearing but I thought I'd throw that in there.

I couldn't hit my target AFR trying to drive up the stock injectors with the VAFC, so I installed 310cc Accel injectors and use the VAFC to dumb them down to target AFR.

The battery charger should not damage the ECU. But it may have triggered another issue... any time I start seeing things like you describe, I start to question the hardware of the ECU itself. the most common thing is the electrolytic capacitors. (they get old and need to be replaced) The larger ones help power supply stability which would cause a lot of what you have mentioned with both ECUs. Have those been replaced?

They have not.

I have been looking at the kits but wasn't sure if it would help. They are cheap so I suppose it wouldn't hurt to give them a shot on the P72. Correct me if I am wrong but it is my understanding that the JDM P30 has surface mounted components so I am not sure I am up to the task of trying it on the P30.

JDM ECUs have through hole caps in them that should be replaced due to age.
Since you have two ECUs that are the same approximate age, you may want to make a list of values and source the parts yourself. It may be cheaper than one of the kits. Digikey or Mouser are great sites for that sort of thing.

Just for my own clarification on your above response....When you say "any time I start seeing things like you describe" I assume that would apply to the issues I am seeing on both ECU's? Not necessarily one of them in particular?


ETA: Disregard this post....I see you have already answered this question.......Pay Attention to detail...stay alert, stay alive!....
I just don't see a way to delete this redundant post.....

So just crack them open, Identify each and every cap with its value/tolerance (caps only?) and order them up? Is there some kind of resource that identifies all the caps and where they are located on the boards? It would be helpful to know that I am not missing something and or where to look to identify what I need.

Also on a side note since I am potentially sourcing electronical bits....The NTK L1H1 wideband O2 sensor plucked from the original VX motor in my hatch that I was using with my DIY-WBO2 finally crapped out. The OEM sensors are quite pricy. Is there a good compatible sensor at a reasonable cost I can use with my DIY-WBO2? Or bite the bullet and get another NTK L1H1? (ouch).

I am pretty sure it is the sensor. When I turn it on my heater circuit LED lights up, but I get zero voltage on the output of the UEGO. I need to check the Helms for a test procedure for the wideband to make sure, but I am fairly certain it bit the dust. That or my circuit board had a fritz.......I do have another complete kit however as I bought 2 of them at the time of original purchase. (As a side side note, I also still have a bunch of the documentation, parts list and schematic stuff also...if that is at all useful).

The username Blundar comes to mind.

uF and V values on the part itself. (microfarad and voltage)
And yes, all of the can shaped caps, I usually just replace the larger ones, unless there is something obviously wrong with the smaller ones.




As far as the L1H1, no idea. I went to a aftermarket wideband and have not looked back.