I got a check engine light again; I checked the codes in A2 and got 315 and 433. I found 315 was the Evap system and 433 was a rear knock sensor.

I currently have a problem where after coming to a stop my car idles really low (doesn't stall) for about 30secs - 1 minute then idles normally. It has this problem more often then not when driving; it doesn't seem to matter if the car is warmed up. Actually after I got the check engine light it doesn't seem to idle low anymore, I assume the engine management has gone into a "default" mode. I’ve already checked my whole vacuum system for leaks and didn’t find any. I also checked the charcoal canister and didn’t see any cracks or leaks.

Would either of these codes cause my above low idle problem? From what I’ve read it seems that the Evap one could cause it, but I don’t see any problems with the canister, and I’ve only received the Evap code once, the rear knock sensor code I’ve received numerous times after resetting the codes.

Are there any real problems with running with a faulty rear knock sensor?

Thanks in advance,
Scott

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Scott K - 1994 850 Turbo

I replaced the knock sensor on my '98 V70. In addition to the CE light, my symptoms were reduced power and gas mileage. To replace it, you have to remove the intake manifold.

Well I did some more research, I think I have bad EVAP purge valve. After starting my car there is a pretty loud hissing sound coming from the front driver’s side bumper, so I put my hand on top and there was a lot air being sucked in from the third valve on the charcoal canister. From what I’ve read this isn’t normal (could someone confirm?). So do I just have to replace the valve or do I need to replace the canister as well?

Thanks in advance,
Scott
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Scott K - 1994 850 Turbo

There is an upgraded purge valve, you do not have to replace the entire canister.
As for the knock sensor, if it only sets a code when you put a strain on the engine, switch to the next higher level of octane when you tank up. If you are using premium, have a mechanic check the electrical impulses of the sensor before replacing it.

Klaus
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(V♂LV♂s 1975 164, 1995 854T, 1998 V70R)

You can disconnect the line to it and see if there is charcoal dust. If so, replace it, if we are talking about the same one. It is small, and in the lower front of the engine compartment on the drivers side.

Your Evap code could be coming from a loose gas cap or a bad o ring that isn't sealing when you tighten it down. I can't imagine that would be affecting your low idle though. Maybe these other gurus have some ideas. You may also wana look over in the 700-900 FAQ in the rear wheel drive forum. A lot of good info about trouble shooting various engine problems.

bl