ECU goes to fail-safe mode, but only once engine is fully warmed?

[JNM240]

Ok, im having a problem. Not sure when it started, but i believe it was before installing NIStune. I havent been able to drive the car normally for nearly 2 months now.

Anyway, start the car from a dead cold (like sitting overnight or whatever), and it starts and runs GREAT. Once the car is fully warmed up, for some reason it goes into fail-safe mode. It boggs, misses, backfires and RPMs will not get over 2k. The only ECU code present then is the knock sensor, which i am sure is misleading due to the poor running. To verify that it is most likely NOT the knock sensor, i disconnected it, then i copied the normal fuel and timing maps over to the knock fuel and timings maps on NIStune, so that if it were engine knock causing the problem (at extremely light load and good AFRs, doubt it), then when the ECU switched maps to the knock map, it would continue to run normally, since it would be using the same map as normal.

I have checked continuity from the MAF pigtail to the ECU, and verified power and ground at the pigtail. The MAF was working, is it possible it just died? If so, then how come it only acts up when fully warmed up? I am not getting any code for coolant temp sensor, and that remains normal the entire time.

Whats going on? Anyone have any insight? BTW its a N62 Z32 MAF, if it matters.

Thanks,Jason

[boost_boy]

Ok, im having a problem. Not sure when it started, but i believe it was before installing NIStune. I havent been able to drive the car normally for nearly 2 months now.

Anyway, start the car from a dead cold (like sitting overnight or whatever), and it starts and runs GREAT. Once the car is fully warmed up, for some reason it goes into fail-safe mode. It boggs, misses, backfires and RPMs will not get over 2k. The only ECU code present then is the knock sensor, which i am sure is misleading due to the poor running. To verify that it is most likely NOT the knock sensor, i disconnected it, then i copied the normal fuel and timing maps over to the knock fuel and timings maps on NIStune, so that if it were engine knock causing the problem (at extremely light load and good AFRs, doubt it), then when the ECU switched maps to the knock map, it would continue to run normally, since it would be using the same map as normal.

I have checked continuity from the MAF pigtail to the ECU, and verified power and ground at the pigtail. The MAF was working, is it possible it just died? If so, then how come it only acts up when fully warmed up? I am not getting any code for coolant temp sensor, and that remains normal the entire time.

Whats going on? Anyone have any insight? BTW its a N62 Z32 MAF, if it matters.

Thanks,Jason

Dee scratches head on this one . Try testing the voltage of the AFM with the ignition on, but engine not running. This is done with a voltemeter and you or some device blowing air at the hot wire to see if the afm's voltage output is increasing like it's supposed to.

Dee

[JNM240]

I can watch which cells the ECU accesses for fuel, and once it warms up and starts acting up, it never increases in load. But it acts fine until then...

[boost_boy]

I can watch which cells the ECU accesses for fuel, and once it warms up and starts acting up, it never increases in load. But it acts fine until then...

Crank angle sensor, AFM and ecu all have the ability to cause your symptoms. Something's not happy, but I am stumped on this one. It all starts with your NISTUNE application. Hopefully one of the guys who use NISTUNE will chime in and help you with this one.

Dee

[JNM240]

Ok, does the MAF have an intake air temperature sensor? Guy at work seems to think it does and if this goes out, it would cause my problems.

Will definately do the blow-thru test tomorrow tho. I know its 0-5volts, but all i can do is physically blow thru it, as long as the voltage moves upwards, that means its ok?

[D_Stirls]

Since you can what the sensor outputs while it is playing up, what is the AFM voltage doing when it starts playing up.It won't be the CAS, if the ECU doesn't get the CAS signal the engine won't fire.

With the Det' Sensor it a ground signal, if you cut the wire it will garentee there is no signal gets to the ECU and therefore run normally.What i mean by this is that the ECU only gets a signal from the Det' Senosr when a Det' event occurs, the rest of the time the ECU doesn't see a signal from it. So by cutting the wire the ECU will just think that everything is fine

[float_6969]

That's not true. The ECU can tell if the knock sensor circuit is open and will throw a fault code and pull timing.

I know it's not throwing a code for it, but I would replace the temp sensor.

[D_Stirls]

Modified by D_Stirls at 6:51 PM 8/18/2009

[JNM240]

Ok, to anyone who is using NIStune, i have a question:

On the standard Consult display gauges, what is the last bar graph that says FTemp? What is FTemp? When i crank the car up, this is already maxed out. This may be my problem. The engine temp (first bar graph) reads fine the entire time, its just the last one, FTemp, that is maxed out straight off.

[Seishuku]

Try replacing the knock sensor.It's ignored until the engine is up to temp, once it's there, the ECU tries to pull a reading from it and is probably just getting static or junk back and tosses out a code.

I'm currently having the same problem on my SR, so I disabled it until I get a new one (copied normal timing maps over the knock timing maps).

[JNM240]

Ok, ive done the same thing: i disconnected the knock sensor and copied the normal fuel/timing maps over to the knock fuel/timing maps, so that if knock were actually detected, the ECU would have no place to go. But it still acts up exactly as before.

So like i asked previously, what is FTemp on the Consult gauges display in NISTune? Because that reading is already maxed out even before i start the car. The engine temperature is reading normally the entire time, so i dont think its the coolant temp sensor. Does FTemp have something to do with the air intake temperature? Like maybe measured at the MAF?

[Seishuku]

I think FTEMP is the fuel temp, shouldn't be used on a CA.

Was the MAF and coolant temp readings correct?

[float_6969]

It is fuel temp. N/A for the CA.

[JNM240]

Finally fixed my problem. Turns out it had nothing to do with the ECU or the Z32 MAF. Apparently the #3 ignition coil would stop firing once the car fully warmed up. This was very odd to me because it wasnt a dead miss, it was more like bogging down, very poor throttle response, no boost, wouldnt free rev or get over 2 grand (maybe a little over, but it was murder getting there!). And it was throwing a knock sensor code, even though that cylinder was getting fuel, just no spark. So after all that, it was one ignition coil!

I ordered a new coil from Autozone, it came in today and i put it in, drove it around for a long while, and it seems to be fixed! Thank you to all who gave advice. My only advice is, its never something obvious, and the symptoms NEVER fit the problem!!

Jason