P0171 (too lean) on 2002 V70 non-turbo

zwieback · Post by **zwieback** » 30 Jul 2018, 21:28

I recently got a P0171 on my 2002 V70 non-turbo, 170K miles. I did a few overdue things like replace the fuel filter but the code came back. I inspected the usual vacuum hoses and sprayed carb cleaner, all inconclusive. The log from the Torque app also doesn't clearly point to vacuum leaks.

Last couple days were hot and I took longer drives and now I'm hearing a distinct whistling when the car is warm, even when it's idling. Pulling the dipstick makes the noise go away but I don't see smoke.

I read some of the threads on using glove test for PCV testing so I tried that. I get a super-hard vacuum as soon as I start the engine, I was afraid the glove would get sucked past the little grill they put in the top of the oil filler.

Now I'm confused, I read that the PCV system is different on non-turbo and excessive vacuum and whistling point to bad PCV but I don't understand why these symptoms show up and whether I should diagnose further before taking the PCV plunge.

I should add that I'm going to "sell" the car soon so I'm not planning anything heroic seeing that it's worth maybe 1.5K$ at this point. Still, I've grown attached to it and it's otherwise solid so want to give it a decent send-off.

Thanks,
Andrew

Post by **oragex** » 30 Jul 2018, 23:54

Did you had the car from new? If the PCV is original, it's long time overdue. In theory if there's vacuum the PCV works fine

The brake booster cabin seal can start leaking and will whistle in hot days (can be heard inside the cabin behind the dash board)

There may also be other vacuum leaks, maybe inspect the hoses near the throttle body

The non turbo have a problem with the intake air thermostat www.youtube.com/watch?v=gOx3Q8vqoz4

Also good to check, the downpipe flexible starts leaking at this age, and this can fool the oxygen sensor reading

dj_v70 · Post by **dj_v70** » 31 Jul 2018, 04:15

I had the exact same symptoms on my 2003 non-turbo. The PCV oil trap box had a ripped diaphram. That is highly likely to be your issue also, you need to replace oil trap. Really stupid design. Another poster suggested that the engine will be damaged by driving car in that condition.

Post by **abscate** » 31 Jul 2018, 04:26

If you have a tool that can monitor short term fuel trim you can test for vacuum leak by

Looking at short term fuel trim at idle, then looking at about 2500 rpm.

If the trim goes down to less than3% or so at 2500 rpm, you have a vacuum leak.

..,and my guess is you have a simple vacuum leak . The best way to find it is systematically remove and replace it with cheap hose from your friendly local auto parts store, or FLAPS

dj_v70 · Post by **dj_v70** » 31 Jul 2018, 06:37

Abscate,

I am willing to bet a beer on the PCV oil trap. Normal vacuum leaks won't give you the high crankcase vacuum that I/OP have. I just did this on my car a month ago. There is a lot of bad info on net, including here, that says you can never have too much crankcase vacuum. This isn't the case.

I had the whistling and high crankcase vacuum. PCV oil trap is the fix.

zwieback · Post by **zwieback** » 31 Jul 2018, 07:53

Thanks for all the suggestions, I put 130K of it's 170K miles on the car and never replaced the PCV so it's overdue. My STFT does not go low at 2500 but it also bounces around like crazy sometimes. I'll do another more controlled test and look at the other seals but with the info from dj_v70's posts this thread I'm leaning toward PCV replacement. The kit is pretty cheap and the project looks fairly doable although I hope I don't have to drop the oil pan in the end.

Post by **oragex** » 31 Jul 2018, 09:34

With the risk of repeating what others say, make sure to replace the box even if it feels light and empty. Also inspect the lower block engine port and blow some air in there (see youtube)

Post by **abscate** » 31 Jul 2018, 09:41

There is a lot of bad info on net, including here,

Im standing proudly by my 1:9999 track record.

I think you are right - plugged block port.

Post by **chrism** » 31 Jul 2018, 15:29

If the whistling stops by loosening the oil filler cap or by pulling the dip stick out, then the problem is most likely an over-vacuum situation in the PCV system and not a vacuum leak in the regular intake path. The vacuum control diaphragm on the oil separator box would be the prime suspect. I've also been down the same road with my 2003 2.4 NA:

https://www.brickboard.com/AWD/volvo/16 ... rical.html