Intermittent Afr p1166

[bemmis]

- EP3
- PND 2062-600830 (replaced original PNF while troubleshooting)
- Kmanager 4.6.1
- The car has had the wiring modified for racing with most of the non-engine systems removed. The power and ignition are wired with toggles and the start is activated by button. A key is no longer used. A 50a breaker on the + lead connects the battery to the car. The fuel cell pump is wired directly to the battery and not through the ECU. It has worked in this condition for 3 years, since install and dyno tuning with no known problems.
- purchased 8/17 from King Motorsports, WI

The car ran normally last year. After a bent valve and engine rebuild, the car does does not sense afr.

Seemingly randomly, after no changes, the car occaisionally reads afr. This happens about 1/15 starts. The car also intermittently triggers p1166, and has triggered p1134 once at the same time as p1166. There was no change to the wiring or any part of the electrical system. P1166 occurs about 1/15 starts, but there is no obvious correlation to afr reading.

The alternator was modified this year to clear the intake manifold plenum. The voltage regulator was damaged. Before it was detected, the engine idled in that condition for about 5 minutes. Voltage was datalogged at 14-15, but climbed to 20v at times. Afr has been detected with the damaged alternator, but not the new one. V is normal with the new regulator. See datalogs

After the V regulator was replaced, P1166 troubleshooting showed battery V between e1 and e24. A stock calibration was loaded and the ECU was installed in a known-good stock EP3. Kmanager did not detect ignition on. The ECU was reinstalled in the problem vehicle as Kmanager detected it normally. The PNF board was replaced with a known good PND.

The main relay did not used to be present, with power going to both control and load wires. It ran normally like this for 3 years/1000 miles. With this configuration, the car has never been driven in rain, winter, or dirty conditions. After the board was swapped and no change in observed datalogs values were observed, a main relay was installed and wired as stock. This is present in the second datalog.

The engine harness has had EVAP and SO2 removed. The junction block at G101 was replaced with a soldered connection and the ground relocated to an M8 boss on the cylinder head near the ECT sensor. This configuration has been present for 3 years and worked normally. The engine, although the wiring for it is still there.

The battery and fuse boxes are in the cabin. This was done through lengthening and shortening various wires. All connections are insulated and soldered and have been checked for quality and corrosion while troubleshooting. The battery cable is 2ga and routed along the rh side of the subframe. The transmission is grounded via the M8 battery tray bolt hole with 4ga. The Engine is grounded to chassis via rh engine mount bolt to the rh engine mount structure with 4ga and an m6 bolt. All grounding contacts in the engine Compartment have been cleaned while troubleshooting.

Notes:
So2 V has been present since afr was last readable. O2 V has not been present. There is no S02 sensor in the car and nothing is connected to e4 or e6. The MAP sensor is NGK. See abnormal MAP value after engine shutoff. See abnormal cam angle value at startup. Ignition and puel pump have toggle switches for power and operate on separate circuits.

Thanks!

[Spunkster]

If the ECU was tried in a known working vehicle and it is not showing ignition on, it sounds like the ECU is damaged and would need to be replaced. With all the wiring modification there is a chance that you may damage a replacement ECU when it is put in this vehicle.

[bemmis]

The ECU was replaced for that reason - not sensing ignition on in a known-good vehicle indicates an ECU problem.

The wiring changes aren't significant, although numerous. It is simply removed components like power windows, wipers, AC, etc. The only component change to the engine harness is the EVAP and so2 removal. The harness was used without issue for a long time.

What might be helpful here is insight into how the ECU works internally in order to give greater meaning to the symptoms described. Battery power between A1 and A24, or MAP sensor V not stabilizing after engine off, for example.

[bemmis]

I have still not resolved this issue. If there is a suggestion more specific than the problem possibly being related to something in the wiring, that could be really helpful. Please feel free to ask any questions or to request any cooperative action on my part. Thanks.