Hi Richard, thanks for the reply. First, I don;’t use an oiled air filter, so we can rule that out. I did change the air filter, even though the previous one wasn’t particularly dirty or old. I use OEM Mann filters. I have had this car since it was new. Speaking of “new”, the MAF sensor is reasonably new too, and it’s a Volvo OEM part.
Of the other common causes, the code is extremely intermittent. Most P0172 code problems are persistent, not once every two or three hours of stop-and-go driving.
I am thinking this is more on the vacuum leak side, rather than the fuel delivery side. I have a fuel pressure tester, but the 850 fuel rail required a 90deg Shrader valve adapter I don’t have, the throttle cable plate prevents using a straight connector. I should have the fitting tomorrow.
Strangely, I was getting a P0456 Small Evap leak detected code. I seemed to have fixed that by replacing the original gas cap, after nearly 25 years of faithful service (-: As soon as that went away, I started getting the P0172 code. Literally, right away, after driving for 30 miles or so around town.
I am too old to believe in coincidences. Do you see any connections that might point to a common cause? I ordered a smoke tester…
- This reply was modified 10 months ago by Don Bishop. Reason: added detail about MAF