Video: Hunting throttle during OEM coolant burp procedure

[carfreak85]

After replacing my radiator I started with a distilled water/white vinegar mix, then three rounds of water flushes. On the water flushes I used the factory-preferred method and had some pretty interesting results.

Before I explain what happened, let me tell you what did NOT happen:

• The engine did not overheat.  The temp gauge didn't budge above normal at all after reaching operating temperature. I attribute this to massaging the radiator hoses a whole bunch before capping the system each time.

• The check engine lamp never came on. As in, not once. Not even a flicker.

• I did not change throttle position at all when the phenomena began, until noted in the video.

• It was repeatable enough to happen on three consecutive "burps."

So, what did happen? About 6 or 7 minutes into my 10 minute burp procedure, I would lose control of the throttle. Mind you, this is a drive-by-cable throttle, and I hadn't changed the throttle position at all.

When this happened the rpms would drop down to about 1,250, then up to 1,750 rpm and repeat until I either floored the throttle, or backed out and let the engine idle.
 

What the hell is going on?

 

[1 Lucky Texan]

hmmm

 

did the rad fans cycle on-off?

Edited March 25, 2015 by 1 Lucky Texan

[carfreak85]

Yes, although it was hard to hear over the exhaust.

[carfreak85]

I had one fellow on NASIOC suggest that it could be an IAC gasket issue, but I don’t have any sort of idle problems.  The engine has only misbehaved during the coolant burp procedure.
 

[Fairtax4me]

Was the battery disconnected while doing the work?

 

Also What year? and does it have Electronic throttle?

Edited March 31, 2015 by Fairtax4me

[carfreak85]

2002 WRX, drive-by-cable.

 

Battery was connected, car was running when it happened.