New to website, have question about surge

[boxterfan67]

Sometimes when I go to park my 02 H6 LL Bean wagon, the engine will involuntarily will surge while still in Drive. It happens when I am almost at a complete stop. I have come to anticipate it, but I worry when others drive my car (such as my barely 16 yr. old son). Any suggestions?

[plain OM]

Does the "surge" occur when turning the steering wheel while parking? If you haven't noticed, check it out and let us know.

A properly operating engine is finely tuned. When it's idling with no load, all the variable parameters such as timing, throttle, injector pulses etc are adjusted to minimize fuel consumption and emissions while still ensuring the engine continues to run. But this is a fine balance.

When the steering is turned and when the car isn't moving, the power steering pump has to work harder, and this loads the engine. As this will upset the "balance", the throttle is adjusted slightly to compensate, and that can be felt as the surge. Incidentally, the same thin happens, for example, when the air conditioner compressor is turned on.

Not saying this is what's happening in your case, but some details on when it occurs, while parking, might lead to this conclusion.

Let us know . . .

[boxterfan67]

Thanks OM... Looking back I think that you nailed it. My idler pulley has been slowly deteriorating, and I notice it the most in the steering at low idle. The draw down of the engine while turning and then "catching up" when the wheel straightens makes sense- (causing the surge) I will replace the pulley and see if that changes anything. Thanks again for your input.

[plain OM]

The accessory drive "serpentine" belt tensioner on the H6 is not an uncommon problem. I'm not sure how it would cause the surging, but if it's been noisy all the better to change it before it fails totally. There's been some cases of that happening, with loss of drive to the alternator, power steering pump and the AC compressor.

[boxterfan67]

I looked at the idler pulley in particular today and it has a slight wobble when the engine is running.I'm sure that the wobble is keeping the belt from moving properly, since it wouldn't have contact with the pulley 100% of the time. Guess what accessory is first in line after the pulley....you got it! The power steering pulley is the very next one. Ironic, seems that one of my vehicles always needs something right around Christmas!