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Seeking engine electronics advice!

psbnsx

psbnsx

Contributing Member
Joined
4 October 2004
Messages
171
Location
Albuquerque and Santa Fe, NM
Hi, Everyone

I have a 2001 NSX fitted with a supercharger and an AEM F/I controller. One morning I started the car and the engine idled erratically, and "CEL" came on with the codes for "Crankshaft Position Censor malfunction" and a "MAP sensor low input". Prior to that morning the car ran flawlessly.

First, the Crankshaft Position Sensor was changed and the problem persisitsed. Next, the AEM F/I controller and wiring harness were changed, but the problem still persists: erratic idle and CEL is still on.

All the usual things have been checked: loose ground wires, resetting the ECU, vacuum lines, resetting the OBD2.

What's next? Replace the ECU?

If anyone has any ideas on what to do next I would greatly appreciate reading your replies.

Thank you!

Philippe
 
Thanks for the replies!

Yes, the new F/I controller was programmed before it was installed. Unfortunately, it made no difference. And the connections have been checked.

Anybody else have any suggestions? We're getting pretty frustrated here!

Thank you!

Philippe
 
How long did the car run with the F/IC installed & running correctly? What S/C are you running? Have you checked the intake for carbon build up yet? I've got a '00 with SOS S/C F/IC running well for almost 2yrs I have a couple quirks but nothing like you described. Would have loved to do the AEM series2 but wasn't exactly available back then.
 
My car has 43000 miles, with only 3000 miles since the SoS supercharger was installed last March. Like I said, it ran perfectly until one morning when I started it and quit running properly.

Thanks for your reply!

Philippe
 
Do you know anyone with a 97-01 NSX close by that you can swap in a known good OEM ECU prior to buying one from Honda?

This way you will know if the part is needed or not, the only other thing to check is to ohm out the OEM harness it self, I have had issues with older cars and mice chewing the engine harness while in winter storage.

Dave
 
psbnsx said:
My car has 43000 miles, with only 3000 miles since the SoS supercharger was installed last March. Like I said, it ran perfectly until one morning when I started it and quit running properly.

Thanks for your reply!

Philippe
Click to expand...

Sounds like we might be running very similar setups. I had some initial issues after install with bad grounds near the ignition detection module (near the alternator) they were causing me some weird issues & random CEL's. Buy chance did you also do the SOS intercooler? If so did you splice and extended the ignitor plug I'd check the connections and grounds near this location as well. You mentioned also having MAP sensor code have you checked the F/IC MAP clamped voltage is correct? I believe on the stock ECU its around 2.8v on the map sensor? Did you tuner have any issues tuning it in the beginning?

Have you contacted Chris@SOS for some other suggestions yet?
 
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Hi, everyone

Thanks for your replies. They are appreciated.

Here's an update. Today the AEM F/I controller was completely disconnected from the car. The car was then started with just the factory ECU in place. The engine idled smoothly without CEL's on (although it ran very rich). Now I know this is not the solution, but it does seem to me to point to an issue with the AEM F/I controller.

Now, I'm not a mechanic. Does anyone have any ideas what to do next? Bear in mind that I have 2 similarly programmed AEM units and wiring harnesses that seem to be causing me problems.

Thank you!

Philippe
 
If you have bigger injectors, it will run rich with the stock ECU. Have you reflashed the ECU? Re-install the firmware etc etc? Start from scratch...
 
Hi, everyone

I am considering taking my car to a tuner/dyno shop that has experience with AEM F/I Controllers. It is located about 2 miles from my car.

Can I drive my car there with just the factory ECU controlling the engine? The AEM unit is currently disconnected. Obviously I am wondering if I will hurt anything by driving a supercharged car without F/I box installed.

Thanks!

Philippe
 
Dumb question but have you swapped out the main relay for a known good one? This would take all of 5 minutes. Have you checked fuel pressure?

It does seem strange that once you disconnected the F/IC the car runs fine.
What injectors are you running?

I don't think I'd drive the car. Flatbed it.
 
psbnsx said:
Hi, everyone

I am considering taking my car to a tuner/dyno shop that has experience with AEM F/I Controllers. It is located about 2 miles from my car.

Can I drive my car there with just the factory ECU controlling the engine? The AEM unit is currently disconnected. Obviously I am wondering if I will hurt anything by driving a supercharged car without F/I box installed.

Thanks!

Philippe
Click to expand...

Sounds like your having problems with the F/IC itself or the tune on it, I would double check the wiring harness see if any of the connections or pins have come loose. I've heard of pin being pushed out when plugging in the harness etc. Very rare that your 2nd replacement F/IC would be giving you problems. I was going to say if you unplugging the F/IC and the car is running on factory ECU then you might start looking for mechanical issue such as checking that you haven't jumped the timing belt etc.

If you are running the RC 550CC injectors I would flat bed it to the shop, there is no way for you to scale the injectors without having the F/IC connected. It will run way to rich and might cause you new problems if an attempt to drive it under those conditions like fouling your Cats and O2's.
 
you might start looking for mechanical issue such as checking that you haven't jumped the timing belt etc.

Is this procedure explained anywhere in the service manual?

RAY.K with the "barn find" nsx lost power after visiting the dealership. The final diagnosis they mis installed the timing belt
and Ray had a bad fuel pressure regulator. While it's at th dealer, have them check the FPR.

Here is the quote from Ray.K : Replaced the fuel pressure regulator and pressure is back to normal. Apparently the faulty regulator was causing the injectors to "over-inject" and thus caused the car to burn rich. He also mentioned something else heating up/overheating but now the temperature is normal. I'll ask again.

I also found this from Larry B. You may need a new Fuel Pressure Regulator. Sometimes with age they leak down and send most of the fuel back to the tank instead of keeping the fuel rail pressurized. If there is anyway you can get a fuel presure gauge on it for a while, and after it will not start, check it while you are cranking it may tell you something.

You can find the thread here: http://nsxprime.com/forum/showthread.php?t=94278
 
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Hi, Everyone

Thanks for the replies.

The engine does run smoothly with the F/I box disconnected, and poorly with either F/I box attached.

I am currently attempting to get a tuner to come to the car. I would like for him to plug his laptop intp the F/I box and see what useful information can be obtained while the engine is running poorly.

I'll certainly keep you posted!

Philippe
 
kookoo4nsx said:
you might start looking for mechanical issue such as checking that you haven't jumped the timing belt etc.

Is this procedure explained anywhere in the service manual?

RAY.K with the "barn find" nsx lost power after visiting the dealership. The final diagnosis they mis installed the timing belt
and Ray had a bad fuel pressure regulator. While it's at th dealer, have them check the FPR.

Here is the quote from Ray.K : Replaced the fuel pressure regulator and pressure is back to normal. Apparently the faulty regulator was causing the injectors to "over-inject" and thus caused the car to burn rich. He also mentioned something else heating up/overheating but now the temperature is normal. I'll ask again.

I also found this from Larry B. You may need a new Fuel Pressure Regulator. Sometimes with age they leak down and send most of the fuel back to the tank instead of keeping the fuel rail pressurized. If there is anyway you can get a fuel presure gauge on it for a while, and after it will not start, check it while you are cranking it may tell you something.

You can find the thread here: http://nsxprime.com/forum/showthread.php?t=94278
Click to expand...

psbnsx, did you do your timing belt as well? How many miles on your car now? I did my tb/water pump on mine same time we did the S/C.

Sounds like he may have found his issue possible F/IC problems. The SOS S/C doesn't not use a FPR like the comptech kits, it utlizes a walbro pump with 550CC RC injectors using a 1:1 factory FPR I'm running ~around 60psi at peak ~9.5-10.5psi here in Southern Ontario, Canada. I guess if the factory OEM FPR went bad you'd have some issue as well, but not sure it would throw a CEL Crankshaft Position Censor malfunction" and a "MAP sensor low input", these are items the F/IC specifically adjusts delaying timing etc. Almost sounds like these settings are not being intercepted correctly by the F/IC itself, or the factory ECM is not getting them altogether. Have you or your Tuner tried the bypass plug on the F/IC yet?

Refer to the '02 service manual Ignition "Timing Inspection Section" 23-91, & 6-18 "Timing Belt Installation". I would check it taking the timing covers off rotating the belt by hand and check to see all the timing marks making sure they line up still on the Cams and Crank etc.

Don't forget to let your Tuner know about these things: http://www.nsxprime.com/forum/showthread.php?t=152810

Did you try to reset the ECM/ECU yet Service Manual Section 11-38/39? If you decide to try a differnt ECM/ECU, "The ECM is part of the immobilizer system. If you substitute a known-good ECM, the ECM will have a different immobilizer code. In order for the engine to start, you must rewrite the immobilizer code with the Honda PGM TesterThe ECM is part of the immobilizer system. If you substitute a known-good ECM, the ECM will have a different immobilizer code. In order for the engine to start, you must rewrite the immobilizer code with the Honda PGM Tester"...
 
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Hi, everyone

Thanks to everyone for your input.

Tomorrow I plan to take my car to a local dyno/tuner establishment. They have experience with AEM FIC boxes. We plan to connect their laptop into my FIC box and read the data as the engine is running. Perhaps this will lead to a solution of this vexing problem.

I'll post the results.

Philippe
 
Hi, Everyone

Engine will not start now. I can't take it to the tuner. Things are going from bad to worse!

Maybe there's something to be learned from this new development.

Philippe
 
psbnsx said:
Hi, Everyone

Engine will not start now. I can't take it to the tuner. Things are going from bad to worse!

Maybe there's something to be learned from this new development.

Philippe
Click to expand...

When attempting to start is the engine turning over, do you hear the clicking of the main relay, and fuel pump relay, and fuel pump buzzing, and is the starter engaging? Have you checked the battery for proper battery voltage etc?
 
Hi, Everyone

The mystery is solved, and now my car in on the mend.

To recap: My Check Engine Light came on. The codes were: P0335 (Crankshaft Position Sensor failure) and P0107 (MAP sensor low input). The engine idled erratically, and the exhaust smelled horribly.

The cause: The AEM F/I Controller failed. Only a new FIC box fixed the problem. My car had no other issues; ie, no loose wires, no disconnected vacuum lines, no nothing. Why the FIC box failed is a mystery.

Unfortunately my cats are destroyed, but they will be replaced.

It seems no other supercharged NSX has experienced this issue. Let my misfortune help the next NSX owner quickly solve his problem if the same CEL codes appear. I hope this post may save somebody countless hours of fruitless searching for the cause of these codes.

My thanks to Scotty at Motiva Performance Engineering in Albuquerque for diagnosing and correcting this issue. My thanks to all of you who posted ideas on what could be my problem. Who would have thought my FIC box could fail?

Philippe
 
Yes, only the third FIC box fixed the problem. That's odd, isn't it?

Once I bring the car home I hope the FIC boxes can be evaluated for defects. We still don't know why the original box failed, or why the second box didn't work either. Right now the car and the FIC boxes are at the shop. The cats have to be replaced before the final tuning can be done and the car brought home.

Philippe
 
http://nsxprime.com/forum/showthread.php?t=154927&page=2&highlight=timing+sensor

Did you check to see if your crankshaft sensor melted?

Yes, it actually melted. So now I'm really going to plan on ceramic coating the engine parts to control where the heat is and to direct the heat.

attachment.php


This is the cheapest place that I found the replacement:

http://www.ebay.com/itm/NEW-CRANKSH...URA-NSX-T-ZANARDI-/270582546856#ht_500wt_1158
 
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