My son called from school to advise the 2.5TL was running barely. It stopped while driving and barely restarted after sitting for a while. He struggled but got home where he has an old PU to drive till I can get down to CC, TX and fix.

When I got to inspect the car, I first checked for OBD2 codes w/ my OBDSCAN unit. I have the CEL always on due to a persistent P0740 that is not repairable, so you don't know if there's another code. I checked and found P0113, Open in Intake Air Temperature (IAT) circuit. I went to the diagnostics page of Acura 2.5 TL shop manual, and it said to check by pulling connector to Mass Air Flow (MAF) Sensor (IAT is contained in MAF), shorting the circuit of the IAT ( 2 wires). W/ shorted circuit, the manual says the IAT temp (from OBD2 scanner) should be NOT BE very cold (-22F or less) if sensor is bad. When I shorted the IAT circuit, the reading on my OBD2 scanner was very cold (-40F). When I checked w/ jumper removed the temp was also cold. When I replugged the connector to the MAF/IAT sensor, the reading was near normal (100F it was hot in CC).

So I had a conflicting diagnostic suggesting the problem might be damaged wiring or damage ECU. I checked nearby wiring to the MAF/IAT and all looked good.

What to do?

I checked w/ O'Riellys for a MAF/IAT unit. It was about $130 w/ tax but was not available except by special order. I checked w/ Honda/Acura (CC has no Acura dealer!) and found the prices was $600+. Scratch that source!

I looked online (car-part.com) for a used unit and found one in West Memphis, TN for $20 (that's my kind of price!) and ordered. Cost was about $35 w/ shopping.

It was sent to my son w/i 3 working days, he installed and all is fine so far.

Not to sure what to make of the diagnostic. Either flow chart is in error, or perhaps we did not install the shorting jumper securely (most likely reason IMV) and circuit was open when we thought it was shorted.

One lesson is not to jump to conclusions and start to tearing into parts based on an electrical diagnostic. I knew that lesson from earlier experience and knowing it would be difficult to access the ECU and isolate the circuit. Replacing the wiring harness would be equally difficult.

The low cost used part made sense, as I felt all along the MAF/IAT component was very likely the fault, and at the used part price it made sense to try that solution first. So far it's working, but I've learned that crowing too early can be humbling, so I'll confirm w/ a followup after a few weeks.

Regards

 

Nice review. May add that Japan's UA2\UA3 have MAP sensor instead of US's MAF, and I never heard that something happend with MAP (use native JDMs, ha-ha).

 

Well, as I stated you can crow too early and that's what happened. After driving for 1/2 hour or so on freeway same symptoms appeared. He thinks it may be main fuel relay or fuel pump. He couldn't hear relay when he tried to start.

I'll look at it tommorrow and see what's up.

regards

 

It was apparently the Main Fuel Relay (MFR). I removed (under dash on driver's side kick panel) the MFR and installed a soldered wire jumper across the relay circuit board (Bat-Fuel Pump). This allowed car to start and run for 1-hr w/o problems. However, this patch also energizes the ignition when keyswitch is OFF (through MFR relay) and car would not shut down even w/ key OFF. I had to pull the MFR to kill it. This jumper installation is not a permanent fix, only a diagnostic procedure.

I've ordered a new MFR to replace.

Symptoms were not typical for MFR. It would sometimes start, sometimes not, and sometimes run poorly when started. However while I was there, and fuel pump was not engaging (no sound from fuel tank), it would not start. I cracked fuel supply banjo bolt and got no pressure confirming no fuel pump action. Pump was intermittent and "caught" when I tried keyswitch again and car started immediately and ran OK.

I've had MFR problems on several Honda/Acura's I've owned w/ exception of Acura 2.2CL. It's hard to understand why this simple electro-mechanical relay is so problematic for Honda/Acura. The circuit board cracks which are usually the cause of failure are an easy manufacturing fix to prevent (better soldering and QA). However, the 2.5TL MFR circuit board didn't look bad at all. On some earlier testing, I found significant heat was generated by one of the relay coils. This doesn't make sense either since the power dissapated by the coil should be small (< 200 milliwatts I calculated). Something funny going on w/ these MFR's. I plan some bench tests on some old units I have to see if I can determine where the heat arises.

regards