swombat

Hi, I have an interesting problem with my '06 Forester. After starting when cold it runs fine for about a minute then starts to idle roughly and has a serious lack of power when driven. Once it warms up about 3 minutes later the problem disappears and it drives like normal. The coolant temperature sensor has been replaced and the front 02 sensor has been swapped as well as plugs and leads. I gave it to Subaru Waitara for two days and they gave up when they they couldn't find the problem. When the problem occurs its as if the car is running way too rich. The annoying part is it doesn't throw any CEL codes even when it stalls as a result of the problem. Besides these symptoms it is also making a whistling sound on hard acceleration. I have been all over it looking for vacuum leaks and can't find anything obvious. I have tested the compression hot and cold and it is fine (170). Any suggestions as to what might be causing this would be greatly appreciated.

Aaron'z 2.5RS/WRX

unplug the MAF when it's starting to fail, see if it runs better..

forester06x

Hmm, my car has occasionally had this problem where it idles super low and I'm chalking it up to a bad upstream O2 sensor. If the MAF is dirty wouldn't this problem show itself at all operating temperatures? BTW, unplugging the MAF sensor will throw a code and put the car in "limp home" mode, it will still run but will limit RPMs and go back to factory/default air fuel ratios.

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swombat

Thread Starter

Unplugging the MAF doesn't improve it at all. I notice when the problem happens the timing advance is being retarded significantly. Suspected it may be a bad knock sensor. Unplugged it and it made no difference. Also when the problem occurs I get a pending code for Cylinder 1 and 3 misfires. My initial thoughts were cam angle sensor, Do they one for each bank ? Any thoughts ?

Aaron'z 2.5RS/WRX

No mention of the condition of the plugs...

I read a whistle when accelerating, vac leak.. spritz some starting fluid various places along the intake tract, on a cold, but running motor.. if it revs a bit, it sucked starting fluid.. vac leak, if not, it was a simple test

There should be a TPS and MAP sensor on the throttle body (not 100% on your later model) unplug the MAP and see if things change...

I had similar issue and sure enough, MAP

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swombat

Thread Starter

Unplugged the MAP sensor while it was running rough and it ran worse. The whistling sound is coming from the exhaust so shouldn't be a contributor. Plugs and leads are all OK.

Aaron'z 2.5RS/WRX

Dang...

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Woody '04

If you can't hear the whistle revving still (as when searching for vacuum leak) but it is very noticeable driving under wide open throttle, it's likely your muffler breaking down inside.

can't add more about the rest ... a number of good things to check on.

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