Lean question
 

Out of the blue my old 930 went lean today. Car lost acceleration power, popped a bit and I motored home with part throttle. Cheapo Split Second AFR reader said dead lean or no indication at all. Both pumps functioned. Planed to take fuel pressure reading so let car cool off. Hooked up LM1 first however and was at my normal 12.0 - 12.3 AFR and car ran fine. Think the fuel filter may have debris that intermittantly blocked flow. Any thoughts?

Thanks in advance.

EPS

12.0-12.3 is NORMAL for your car at idle? That's more the minimum you should be at full boost enrichment, not at idle. That doesn't sound right.

Any blockage in the fuel delivery, resulting in reduced pressure to the fuel head, would cause low system pressure and be reflected in low WUR control pressures, and thus rich conditions.

Do you have the gauge setup to do the WUR system/warm/cold//boost control pressures? Quick and easy diagnostics to at least rule out the WUR, etc. You may have just dislodged an intercooler O ring which will reek havoc on your mixture, so don't forget to look there as well. A leaking seal at no-boost conditions will suck in air unwanted and lean things out; on-boost it will leak out the boosted air and cause rich conditions. Bad enough and the car will run like crap-ola.

Those are the first places I would look, to confirm proper fuel delivery and no air/vacuum leaks. After that, look at ignition problems.

mark is right. I had the vacuum plug on the intercooler rupture yesterday. All of a sudden the car is idling low and i hear this hissing noise under accel. she ran like poop. Then i found the vacuum leak and all is well again.

Mark
 

Mark - you are absolutely correct. I wasn't paying proper attention. AFR entirely too fat. Problem solved.

Humble and embarrased thanks

EPS

Oh no...you don't get off the hook that easily! You can't leave us hanging without sharing what you found as the problem:D

Glad she's back to normal. I hate it when my car does weird things 'cause I can't enjoy the drive without worrying about why it isn't just exactly perfect (which, by the way, it is not).

Replaced Waste gate last week
 

Though I don't really think it was a factor I replaced 30 year old stock wastegate with Tial last week. Car has run a bit more tame since. Then yesterday's problem. Foolishly thought 12ish AFR was what I had been running. Obviously not. Plugs black/sooty. Put AFR back to 14.2 cold and problem solved. AFR at 12.0 at 1BAR during acceleration. Back to the snappy response.

Do you think that ultra fouled plugs and new wastegate (.8) might possibly have given the AFR reading on the backside of the curve? Most likely not but then again this turbo stuff is not, obviously, my area of much understanding.

Again, thanks for slapping me enough to get me to wake back up.

EPS

The wastegate in and of itself shouldn't have an effect on your AFR's, except that you're now boosting to only .8 bar instead of 1.0. Assuming you have an adjustable WUR, maybe your boost control pressure at the WUR was set richer to accomodate the higher boost, and by dropping back down to .8bar you may find yourself a little too rich now when on boost. And if your air pressure line to the WG wasn't secure and leaked, it would be the same as an air leak in your IC.

Dry sooty plugs usually fire just fine, unless oil fouled. IF one or more plugs were firing weakly, then possibly you would see that as incomplete combustion and left over oxygen present, thus a higher AFR reading.