Resetting Throttle Body

[hkriel]

I had an interesting experience here with 2001 Boxster. Got the car in 2006, the original owner had got the dealer engine swap (no charge) at 55,000 miles, an oil seal failure not the owner's fault. It has passed smog check (CA) every year, but this year at 102,000 miles car started running poorly, gas mileage down, ECL on, various codes from OBD led me to believe it had an intake issue. Cleaned the MAF, no change. Noticed oil on the intake boots. So ordered parts and did that AOS changeout, not easy. In the process found that the vacuum reservoir connection nipple was broken right off. Ordered that and the 3 way and 4 way vacuum connector. This is where it is interesting.

To change out the vacuum reservoir I saw that I could take off one intake manifold, or I could pull out the alternator. The latter seemed less trouble. Notes on that: to remove the long bolt with the idler pulley on the end, you will want to deform the sheet metal where the engine cover attaches. I used a big crescent wrench to bend it out of the way, and back into place when I reassembled. That let me get the bolt and pulley free so the alternator could come out. Even so that is a very tight fit. But once the alternator is out you have access to the back of the vacuum reservoir and the Phillips screw that holds it in place.

Getting the throttle body out, cleaning it and the intake boots was not too hard. I loosened the clamps, jockeyed the boots to each side, pulled the air horn away from the throttle body, and pulled it out intact instead of trying to take the 4 bolts off the throttle body. Took a bit of work but it all went back together the same way it came out.

Replaced the plugs too, they looked fouled and worn. Hooked up the battery, car started but would not keep running and would not respond to throttle. OBD says, No Codes, PASS. After some time looking for vacuum leaks, missed connections, forgotten parts, etc I found the advice in a forum about resetting the computer and throttle body: turn ignition on w/o starting, leave on for > 60 seconds, turn off for > 10 seconds, start.

That helped in that I got an idle, but still no response to gas pedal. By being patient I found that the system needs to relearn with engine idling for 15 or 20 minutes, what constitutes good fuel air mixture. Not until I let it run undisturbed would it respond to pedal.