[Don Bishop]

I found a leak on the vacuum tree on the intake manifold by the throttle cable assembly. I fixed that and after 35 miles of driving it’s not throwing any codes. I will drive it a bit more, and if it stays off for another 50-100 miles, I will comment that this is closed. So far it seems to have been related to a leaky fuel cap which was throwing a P0432 low leak EVAP and once that was fixed, it changed to being a P0172 too rich code. After the purge valve and sealing the vacuum tree, that seems to be cured too.

I have not touched the fuel injectors at all.

I will wrap up this thread for posterity in the next day or two if the codes stay clear.

• This reply was modified 4 years, 3 months ago by Don Bishop. Reason: clarity regarding the fuel injectors

[Don Bishop]

I changed the purge valve and the dried-out vacuum hoses connecting it to the intake manifold tree. Problem remains. Next up: Clean fuel injectors and clean throttle body plate. I had a problem with my 2001 V70XC caused by a sticky throttle body plate.

All suggestions welcomed (-:

[Don Bishop]

Fuel pressure is 40pis key on, not running, about 37psi running. Revving ran between 37 and 43psi. No pulsing on idle, steady.

After 30min engine and key off, fuel pressure was still at 28psi in the rail. So I guess I can rule out leaky injectors, although I probably will take them out and clean them anyway while I’m at it.

• This reply was modified 4 years, 3 months ago by Don Bishop.

[Don Bishop]

Hey Richard, Yes, was easily worth the try, good idea. Maybe I’ll put the old gas cap on to see if the code changes back to evap.. Still waiting on the Amazon to show up. And my sense is it’s vacuum related, probably because those problems suck a lot and so does my life ..

[Don Bishop]

Well, rats, that didn’t work. Right at like 20 miles the CEL came back on. No idea what to try to fix, I have to get in the car and drive 20 miles to see if whatever I do worked …)-:

[Don Bishop]

Thanks Richard. I will give that a shot. Heading out to disco the battery. I hope I still remember the radio code….

The fuel pressure tester elbow should be here tomorrow, though I suspect that’s not really the issue — perhaps a stuck injector, I’ll probably clean them regardless.

Then the smoke-tester… Lets hope the reset works (-:

Thanks again

[Don Bishop]

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 4 years, 3 months ago by Don Bishop. Reason: added detail about MAF

[Author]

Replies