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what seems to happen a lot with the MAF sensor is that as the MAF goes bad, its ability to monitor air intake at idle often remains good, while its ability at driving rpm ranges deteriorates. as the sensor begins to fail, the o2 sensors cause the dme to compensate by adjusting the long term fuel trim (lean or rich depending on the MAF error).

once the engine returns to idle, the MAF gets good readings and tries to compensate the long term fuel trim with a short term idle trim adjustment. this short term adjustment throws the CEL (car has richened or leaned the short term trim as much as possible and has reached the 'rich' or 'lean' threshold).

so, if your codes say that the rich threshold is reached, what's likely happening is that the car is running rich at speed, so the long term fuel trim is set to lean it out. once you idle the car, the MAF gets a good reading and compensates the lean long term trim with rich short term trim. bottom line: you're rich at speed and lean at idle.

to test your MAF, turn off the car and unplug the MAF. start the car (it may not idle; you might have to keep on the gass) and go for a drive. if the MAF is your issue, the car will run much better. the DME defaults to a baseline fuel map if the MAF signal disappears.

if you have an OBD II scanner, check your long term fuel trim. in your case, i'd bet $$$ that both banks are running very negative values (i.e. -12% or less) and that the short term trims are both high positive values. this would strongly indicate a bad MAF.

this is almost certainly your mass airflow sensor (MAF). what are your bank 1 and bank 2 long term fuel trims?

There is an outfit in England ( http://www.perfectbore.com ) who make big bore cylinder blocks and pistons for the Boxster/996.  There was a write up in this month's 911 & Porsche World about Autofarm in the UK who are doing a kit to go up to 3.8 litres.  Pricey, though.

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thanks for the info. sounds like fun....

Hi- I keep seeing loose throttle bolts as a cause of CELs -Are these the four bolts that attach the throttle body to the "intermediate piece" (the tee that splits to the two manifolds)?

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Those are the throttle body bolts. 1128 is usually a vacuum leak (likely the oil seperator bellows)

one last thing

what is the best tires to use?

and what is best sizes to use for the front and the rear?

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regarding tire width / rim protrusion: i recently stepped up to 18x10's in the rear. i have used poth PZero Asymmetrico's and Yoko AVS Sport. Both, in my opinion, leave the rim a bit to exposed (tire is a little 'stretched' on the rim width) in 265/35 size. i will likely step up to a 285 next time around.

FYI, i run ET65 offset w/ 21mm spacer for total offset of 44mm. the tire didn't quite clear the e-brake cable on the passenger side, so i had to fashion a clip to hold it out of the way. the tires extend almost to the fender, but don't protrude at all.

as for tires, i agree with 'mee' above; RE750's are an excellent compromise. i used them exclusively prior to this new set of wheels. much cheaper than the pole positions w/ similar sidewall strength and road feel. i still only got about 7500 mi out of them, though...

if the o2 sensors aren't the exact same distance from the cats, you'll get MIL light. my guess is that they are currently too far away from the cats, so the car thinks that the o2 sensors are reacting too slowly.

think of it this way: the car knows the distance between sensor 1 and sensor 2. it also knows the relative velocity of exhaust. say one 'pulse' of exhaust passes sensor 1 and is anylized. the car looks for sensor 2 to confirm this same 'pulse' of exhaust a split second later as it passes sensor 2. on your car, sensor 2 is too far away, so the sensor takes longer than expected to react. the car assumes the o2 sensor is old.

there is also the possibility that the o2 sensor was indeed damaged during removal / replacement. also, porsche oem o2 sensors use the wire itself to 'breathe' clean air with which to compare the exhaust readings, so if the wire is damaged / blocked up, the readings will be bad.

i recommend first unplugging the sensors and checking / cleaning the wire harnesses from the sensors. if that doesn't work, replace the sensor. if that still doesn't work, you will have to have the sensor mounting points moved toward the cats a bit.

Thanks, guys. Doing some 'testing' on air intake mods and the AC data complements the OBD data. All best.

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I remember that there's a sequence of buttons on the AC controller that trigger diagnostic readouts on the AC unit. Does anyone remember which buttons to press and what the readouts are? thanks.

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run the wires throught the center console. the trim around the a/c controls and radio can be popped off by hand. there are screws that will allow you to remove the entire chassis that holds the a/c controls and radio. this will give you the access and the route that you need.

i didn't think that i had an alarm on my car; the option number is not on the hood sticker and my key is just the standard (no buttons) key.

i took out my driver's seat this weekend while installing stereo equipment. under the seat is a component that looks like the one in the photos on this thread. the number on it is M531 though. the part number is 986.618.260.03. Anyone know what this is? thanks.

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Thanks. Figured it would be something like that. My brain just wants to tell me that it can't be THAT hard to get it to work....

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Maybe this is a stupid question, but here goes:

What would be wrong with transplanting a 996 3.6L into a non E-Gas boxster?

If a suitible mechanical throttle body with a compatible 986 TPS were mounted to the 3.6, why couldn't the Box run the motor?

If the answer is DME related, why couldn't an airflow converter be used in conjunction with the DME to trim the fuel?

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not sure whether the boxsters have a self adjusting clutch or not, but if they don't, you may want to ensure that it's disengaging completely.

it doesn't scratch at all.

I know this was an old post, but we always use steel wool.