Engine surge

[Duquette5]

So I've replaced my MAF and WOW! what a difference! The only outstanding issues I have are when sitting at idle it will rev steadily from 900 up to 2500 and drop back to 900 smoothly. This happens every 45-60 seconds. The other thing I have going on is when cruising if I take my foot off the gas pedal the engine bucks for a second. Kinda like its saying "HEY keep it going!"

Here's the work I've done recently (in order oldest to newest all over the last two weeks):
Replaced AOS
Replaced oil and filter
replaced the spark plugs (gapped new at .032)
replaced the MAF

Thoughts and suggestions?

Thanks!
Mike

[Viper10000]

Hey Mike,

Have you tried putting the old MAF sensor back on to see if it still makes those high revs? Just a thought, either it's not the correct sensor for that car or it could be defective? I would be curious with putting the old stuff back on one thing at a time to see if you can isolate the trouble. I take it it wasn't doing this before the work?

[KRAM36]

The MAF sensor has the part number on the side of it. Easy way to tell is just pull out the new MAF sensor and check the part number to your old MAF sensor part number.

[Duquette5]

They have the same part #. Old MAF = BAD JUJU - barely holds an idle until it warms up then bogs down like crazy. I don't recall if I disconnected the battery when I replaced the MAF. Maybe I need to reset it and recalibrate the eThrottle. Imma try that then drive it hard for a bit this afternoon.

[Jamesp]

I had a similar problem when one of my variocam connectors came loose. The car threw plenty of codes when the connector finally fell off, but up to that point it was hit and miss whether or not it was connected and the car was throwing cam position sensor codes. Similar symptoms with a surging idle followed with a stall, one additional item was a very gentle, just noticeable surge at cruising RPM.

[Duquette5]

So I disconnected the battery and recalibrated only to find a nice vacuum leak at the brake vacuum hose. Temporary fix engaged while I wait on a new hose.

[Viper10000]

Great to here you found the culprit!

[KRAM36]

Nice you found the issue. You're going to have a brand new 986 Boxster at this rate lol.