kaltex24

Long time listener, first time caller. I’m at my wits end with trying to resolve this issue with my 1999 Boxster. Apologies for wall of text, the TL;DR is that even after testing multiple MAFs with the car, when I drive it hard after letting it warm up the car either begins to run very rough for no apparent reason or it completely dies while I’m WOT. It does start right up again after cycling the ignition. When I unplug the MAF, the car idles perfectly and pulls strong to redline. Where do I go from here? ECU? Wiring Harness? What troubleshooting steps or reference values are out there that I can compare to? full history of this issue: The first time I had this issue was at a track day last summer. I had a spin earlier in the day (whoops) and didn’t get both feet in quick enough. Took a couple tries to get the car started again but it did the next 2-3 sessions just fine. No CEL, no issues. On the last afternoon run, it felt like it suddenly started to misfire as I neared the top of 3rd gear. I would lose power and the car ran very rough. I got home and had codes p0341 and p1397 for Cam Position sensors (presumably from the spin and stall, oops) and P0102 MAF short circuit/open circuit, according to my durametric readout. My cam deviations remained steady before and after this event. In the subsequent days of driving around the stumbling sensation occurred and it was accompanied by lots of p1128/p1130 for hitting the lean adaptation limit. I ended up doing a fuel pump replacement because it was original, and while it sounded better when it primed, the issue persisted. I even got a rich idle code alongside a lean cruise code. So I ordered a new MAF. This seemed to do the job, and I did another track day and drove the car hard in general without any issues for the rest of 2024. Now in 2025 though I’ve had nothing but headaches. Some days it will be perfect, others it will be shuddery at low throttle and smooth out under load, other days it will barely accelerate and misfires horribly regardless of throttle position. Sometimes my idle hunts between 700-1000 and other days it is right at 740+/- a bit. And then of course sometimes it dies while full throttle with no codes. After these stalls, I can turn ignition off and back on and drive away like nothing happened. But after it cuts out while I’m coasting down I have zero acceleration or combustion events. So far in 2025 I have cleaned the throttle body, replaced a suspect vacuum line to the fuel regulator, replaced my pre-cat O2 sensors (had bank 2 flatline on me, just did both), cleaned the replacement Bosch MAF, and swapped with an OE MAF. Nothing has worked to cure my issues except for unplugging the MAF. I am so tired of not being able to fix this. I feel confident in saying that this is related to something in the MAF circuit since I have experienced stalls while running open loop (WOT should be reduced sensor input, yeah?) and it does not behave like crank or cam since the car starts right up again and I have never gotten another cam sensor code since. But I really don’t know how to check if the wiring harness or DME is the root of my issue. These are expensive parts and I don’t want to get it wrong. Thanks very much for any input or troubleshooting advice.