I was super excited about running with S2K Takeover again at NYST. The weather was going to be perfect, sunny low 70s (though a bit chilly in the 40s in the morning) and we were going to run both the uptown and downtown configuration in open track.
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| NYST 9/1/2023 |
I got about 3 laps in when the car suddenly went into limp mode. I'd seen this before when my oil pressure sensor failed but that wasn't the case this time as all the readings on the car were fine except AFR. I got the car back into paddock shut it off and it started up normally and I was able to drive around just fine. I double checked everything. I wasn't leaking any fluids, coil packs looked fine, I tapped the map sensor in case the plunger was stuck and decided to give it another session. I took a cautious first lap and the car was feeling fine so I gave it the beans one lap and it was running strong then I went to pass someone on the first straight and it happened again.
I decided it wasn't worth pushing the car until I knew exactly what was wrong so I packed it up and drove home hoping I wouldn't have any issues enroute. It drove perfectly fine the whole way (around 130 miles) so I knew there wasn't anything catastrophically wrong with the car. After letting the car cool and giving her a wash, I got her on the lift since I was suspecting a clogged or broken cat might be the issue. I was looking at the cat and the honeycombs looked fine and shining a light through it indicated no clogging.
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| Toasty connector |
I then noticed that the connector for the wideband o2 sensor going to the Haltech looked burnt. The bracket holding the wire had become loose causing the connector to dangle closer to the cat. I suspected that under load when I'm cornering hard this extra play may have caused this connector to get too close to the cat causing it to heat excessively.
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| Possible root cause |
To fix this issue, I relocated the bracket a little bit so that the natural angle of the connector would be flush up against the body. I then added some additional zip ties on the cables so that it wouldn't shift around too much. Now there's several inches between the connector and the cat.
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| Clearance to connector |
I forgot to bring my laptop with the Haltech software to the track so I finally hooked it up to read any codes tripped. Turns out the limp mode was triggered by the oil pressure sender so I grabbed the data log from the racepak dash.
I could see a momentary reading of 10psi at 7700rpm. It was 65psi just before and 70psi after so I'm suspecting these are transient bad values and not actual oil pressure issues especially since this triggered on a straight. My engine protection is set to go into limp when it reads below 172kPa (around 25psi) at 50% throttle above 3000rpm. I changed this now to only trigger at 60kPa (around 8psi) for the same conditions to avoid tripping this under transient readings.
