ONAFLYER

Having issues with my 986 S stalling and bogging randomly. First occurred after a 3+ hour trip to Thunderhill in 100+ temps. No check engine light. Cycling the ignition would reset and be on my way until it happened again.
At the track in the relative cooler morning it did the same on the first lap out.
Had a PWIS scan done at the track and showed p1508. Was suggested possible MAF. New one installed same problem. Same problem with unplugged, though marginally better back home in Reno.

Code has not reset, and no check engine light still.

Also tested fuel pressure, over 50 lbs on gauge.

Thoughts on where I might go next?

ONAFLYER

short video of problem

Macster

Most likely a fuel supply problem. If the fuel pump is not intermitttently cutting out there's a problem with a fuel line -- like a crack/split or loose fuel holse (or even electrical) connection -- that under certain conditions opens up and lets fuel escape or the fuel pump to momentarily lose power.

Not sure if I were in your shoes I'd replace the fuel pump on such thin suspicion although if the engine stalled/cut out under normal driving conditions I'd be tempted.

At the same time a careful check would be made of the fuel lines and connections (even the electrical connections to the fuel pump). This check could be done without having to replace the fuel pump although one wants to be *very* careful when opening up a fuel tank. An flammable/explosive mixture of fuel vapor and air will at some point be present and just a static discharge will ignite it.

ONAFLYER

I have lots of suspicions on this based on how and when it started.

It was initially a sharp left turn, stall. Then a sharp right turn stall. But also in a straight.

On the return drive home through the mountains, nearly every right hand turn produced an issue. Which makes me wonder about fuel pump electrical connection.

Then a few days ago I found a dead mouse in the garage. Maybe it was making a new home in my car somewhere. Time to start searching. Ugh.

Anker

Check the Crank Position Sensor and its electrical connections! Stalling when hot is a typical symptom of a bad CPS!

ONAFLYER

No check engine with bad CPS?

Anker

No, the ECU believes the engine has stalled when the CPS failed and then shuts down fuel injectors, which cause the engine to really stall.

ECU Doctors

A similar thing has happened to us with the Boxsters that we own.

The issue might be a combination of the MAF part number that you installed, together with the correct mapping of the DME.

That's because there are 2 MAF available and 2 maps that Porsche provides to match your setup.

Ask the mechanic that helped you do this to try another map and see if that helps you.

I've personally bypassed this problem altogether putting a 996 map on one of our Boxsters.

Car runs amazing without the all popping.

ONAFLYER

Thanks for the help ECUdoc.

I experienced similar problems years ago, though not as extreme, when I modified everything after a major rebuild.

Air box to plenum was upgraded to 987 S spec, and refused to run right until I had tried numerous maps. Finally got it all sorted and ran great for years til now. I just hope it's not a DME issue.

Richard Jenkins

Had similar problem and turned out mice chewed up some of wires. Took forever to find it since the damage wasn't obvious. Never underestimate the craftiness of those little critters...

ONAFLYER

Turns out it was the crank sensor. After swapping it out, total pita, and a long drive at steady rpm it's all good.
No more issues.

Macster

Thanks for the update.

Those crank position sensors account for more of these types of symptoms than seems reasonable to me.