98 S70 P0172 and P0505 Codes

berley · Post by **berley** » 22 May 2013, 21:58

Normally aspirated, 140K miles, runs fine, new cap and rotor, new crank position sensor, fairly new plugs, genuine Volvo wires look good and they have just been cleaned, all of the vac lines, elbow, etc. (that I can find) look perfect, next project is the flame trap, dipstick is "ajar".

Question #1 Can the gunky flame trap cause the codes?
Question #2 My mechanic friend tell me that a vacuum leak will cause a lean condition but the codes indicate a rich condition. I have read many posts from owners that say they fixed the same problem by repairing a vac leak. Should I believe my friend or the posts?
Question #3 I have checked the following vacuum lines : white line between air filter and manifold, black between air filter and MAF, short black rubber hose from manifold to thingie "A", white with inline filter between manifold to thingie "B" above cooling fan, then purple to thingie "C" at rear of engine, 3 other inlets on manifold are plugged as well as 3rd inlet on thingie "B". Have I missed anything?
Question #4 My mechanic friend also tells me to suspect the MAF. I had the MAF out during the CPS replacement, it all looked so clean inside I didn't bother cleaning it. Are there any tests that I can perform on the MAF to determine if it is good or bad, any repairs?
Question #5 Any other things I should check?

Thanks in advance, Bob

Post by **matthew1** » 22 May 2013, 22:34

Your Volvo is a LPT -- light pressure turbo. P0172 is usually an elbow on the left side of the intake manifold, as you stand looking at the engine with the hood up, on HPT cars. It's the "evil" vacuum line. You'll find a topic or two here if you put that term in a search.

I blew mine off in a WOT run on the highway, and got ~22mpg (low) for a few hundred miles on a roadtrip before I could solve it.

Post by **abscate** » 23 May 2013, 04:54

P0505 shows as an idle air control valve. Easy to clean so I woud inspect that. Anytime there is more than one code, there is a possibility that poor running causes "phantom codes" so solve them one at a time.

When I incorrectly secured my intercooler on my HPT, I got as many as 8 codes at a time including P666....Swedish meatballs stuck in exhaust pipe.

berley · Post by **berley** » 23 May 2013, 09:21

I'll go search again, but I am pretty dang sure I don't have a turbo. I have read previous posts about the evil vac line and have searched for it without success, but I will look again. Anybody have a photo, or a description to help locate the little bugger. I'm guessing it goes down to the flame trap. I have been getting 22mpg "forever".

I will clean the idle air control this weekend.

Thanks a ton to both of you, I will send meatballs to the "winner".

berley · Post by **berley** » 24 May 2013, 02:45

Well, my vin has a 55....dang, no turbo. I did find some pics, and now no where to look for the evil vac line. thanks again

berley · Post by **berley** » 26 May 2013, 21:33

Codes are gone!

Replaced the evil elbow, had a hole right where you said it would be. Did the whole PVC system while I was at it. Other than a couple of hard to reach bolts, it really wasn't that tough a job. Everything just kept revealing itself as I peeled back the layers.

Looking forward to improved gas mileage.

I recently completed 3 significant repair jobs on my S70, thanks so much to everyone that helped. Couldn't have done them without this forum!

Post by **abscate** » 27 May 2013, 05:17

I'll be over to Matt's for Swedish meatballs....

Drop some bucks into the forum donation kitty if you feel so inclined