MarkD

A couple of weeks ago I started having some issues at high boost pressures under load (3rd gear accel). Felt like the ECU was pulling timing or boost. Felt really bad. After a couple more test runs the boost was capped at about .5 bar.
I was concerned.

Then I recalled I had bought fuel at a gas station I don't normally use because I was in an area where there was nothing else. One of those "off brands".
Well, I finally got a chance to finish (gently) running most of the fuel out of the tank today and then filled up at a normal name brand station, Chevron.

I drove around a bit to be sure the previous gas was out of the system and then started some testing. After a half dozen 3rd gear tests, boost returned to the normal behavior pattern. I sure am glad the ECU has a built in safety net.

I would guess that the less than reputable station sold me a lower octane fuel at the premium price. Nice.

I read some threads here that discussed these symptoms but didn't see conclusive evidence that pointed to fuel in the end. I am fairly certain that was my issue though I'd rather not test again to be positive

Just thought I'd post this for posterity in case someone else has the same problem down thee road.

WHB Porsche

Thanks for the info. I believe .5bar is the limit in the ECU's "limp home" mode. Did the Check Engine Light come on?

MarkD

Nope, no CEL. Now that you mention it... wonder why it didn't trip the CEL?

Felix

Nothing wrong with the engine per se so no CEL. I'll check if there's a code for low octane fuel but I don't recall seeing one.

MarkD

don't think there is

but the thing was pulling power back pretty hard. I'll bet there are a long list of knocks logged though.

Felix

It could also have been water if the station's tank was nearly empty.