850 MAF and TPS

[850tech]

Your canister will be in the left front corner, you can get at it by removing either the front lower splash gaurd, or the left front inner fender. Though I would start by looking at the lines in all the area's you've been working around, it just seems likely with all the checks and adjustments you've had to do something may have been unitentionally disconnected or damaged. Start with the canister purge valve, it's attached to the rad fan shroud just under the charge pipe coming out of the top of the intercooler, it's got one line in and one line out the other side. Then check the main EVAP line that runs across the front of the subframe for damage, it runs from the canister in the left front, across the vehicle to the right front and turns toward the rear by the oil filter, it then runs on the inside of the subframe down the right side. Check where it passes under the power steering rack carefully as this is a common failure point. From there it runs all the way to the back and connects to the roll over valve just behind the fuel filter.

If you do have an EVAP leak it will turn on your check engine light eventually, it has to see certain conditions to run it's self test and then has to fail the test on two different drive cycles, so it can take some time to set.

After all that writing it just occured to me..... Is it possible what your smelling is crackcase gases from the previously disconnected PCV hoses?

[Jack Rock]

I came to that same idea about the PCV hose so I'm going to reconnect it to see. I've done some testing on the purge valve. It never seems to close. I disconnected the line on the canister side and started it up, it runs as usual but the valve makes a balloon deflating sound on low revs and high. Same if I hold my thumb on the end of the valve. I tried this with the electrical connected and disconnected which also made no difference on idle except for a little stumble when I connect it. I removed the valve altogether and of course it almost stalls and when I blow into it, it's totally sealed both ways. I'll try to get at the canister and trace the lines but my inner fender is riveted on and I believe the previous owner put an 'R' bumper and associated trim on which also requires drilling out the rivets - not sure I have time for that tonight.

It's my understanding that when not in test cycle the evap canister is at atmospheric pressure so if this valve is not closing then it would allow unmetered air into the manifold and affect the mixture causing high emissions?

Later that day...

Ok, so I decided to drill out the rivets and peeled back the inner fender and I got a good look and feel of the lines and canister. It looked really good in there. I also did some more testing on the purge valve and found it measured 27 ohms which sounds good for a solenoid, I hooked it to battery and it actuated fine. I sprayed some WD40 in it, let it soak, repeat and got some black crud out of it. I hooked it all back up and now it doesn't do the balloon deflating thing all the time just a few pulses here and there which I believe is what it's supposed to do, it's now closed more often than pulsing. I guess that's an improvement, I'm taking it in for a test tomorrow or the next day and I'll see where I'm at. If I fail, it's going to the Volvo specialist.

[Jack Rock]

The gas smell was indeed coming from the disconnect PCV. A new problem arised when I parked after coming from work. The idle dipped to 500 then surged to 1500 then settled at the usual 1000. It did this 4 times about 30 seconds apart. On the fifth time it stalled. I've recently invested in a code reader, plugged it in and found nothing but the 0133 that's been there from day one - a result of running rich or lean I'm told. I also noticed a little smoke coming from the exhaust manifold that wasn't there yesterday, which from what I've read here is yet another symptom of a plugged PCV. So I guess we've verified that I need to do the PCV soon, no problem. I will leave it disconnected for now and hopefully the smell won't be too bad during the test . Sigh, anyway, the test is tomorrow at 5, then it's off to the other shop.

[Jack Rock]

I'm back, one month later and the car is still in the shop. It's summer, volvo shop's busy, vacation, etc. Anyhow, yesterday he put in a volvo cat from a donor car and it passed NOX! Boo to the aftermarket cat that I was coerced into and the other shop too! Still high on CO and HC. Next he replaced both O2 sensors and MAF (maybe other sensors I don't know) from the donor car which were OEM, no change. He's also verified that there are no vacuum leaks and is now scratching his head. Any ideas what's next? Timing? Compression?

[phils94850]

Jack.. did you ever do the PCV repair ? I think thats where id go next...

[Jack Rock]

I'm doing the PCV on my V70 on Monday and haven't done it on the 850 (the one in the shop). I was planning on doing it as a preventative measure but currently don't have any of the tell tale symptoms, no smoke from dipstick or oil leaks. Also, before one of the many tests, I disconnected the PCV line from the intake and capped the port, hence venting PCV gases to atmosphere and sealing the intake. This temporary test, I believe, eliminates the fact that excess crankcase gases entering the intake is causing the rich mixture and failed emissions. How much does timing effect emissions? If I don't have a efficient burn due to retarding timing or perhaps non OEM plugs, could that cause high HC and CO?

[Jack Rock]

This is really frustrating! I can't believe such a good running car is destined for the junk yard. That's the impression I'm getting from everyone I take the car to, still nobody can tell me what's wrong with it. I don't care if the diagnosis is really bad, I just want a tangible answer. Can anyone tell me approximate costs for an engine rebuild or the cost of a used engine?

[850tech]

Ideally I need to see a pre-cat test result to really tell where you might want to look next. A high HC, and CO reading could be both lean misfire or rich induced and the tell tale factor's will be the Oxygen and Carbon Dioxide levels in the exhaust BEFORE the cat has a chance to convert these gases and skew the readings.

Oxygen readings should be about 1.5% (or 3-4% if your car has secondary air injection)
High O2 indicates lean, low O2 indicates rich

CO2 is excellent for determining combustion efficiency, the higher the CO2 the better. You should see above 14%

Solely based on the fact that you say the car runs perfectly my guess is that something is causing a slightly rich condition, and if so the O2 and CO2 will be below normal (PRE-CAT).
A cat operates best in a very specific range and needs O2 to effectively convert HC and CO into harmless H2O and CO2 therefore, low O2 in = high HC and CO out.
Maybe you have a leaking injector or a somethign like a small exhaust leak before the O2 Sensor is inducing a false lean causing the ecm to increase fuel, or even a faulty FPR or restricted fuel return, its hard to say.

Conversely, if it you have high O2 with low CO2, that would indicate a misfire, possibly carbon build up, timing, ignition etc. but again it's tough without the data from the exhaust for me to pin this one down for you and even then I can't say for sure without testing components and seeing a data stream to see exactly what the computer is doing. Obviously with the amount of techs that have looked at this, it's a not so straight forward problem.
I’m really sorry I can’t help more.

to answer you engine cost question try a search on car-part.com for an exact price on a used engine near you, but hear in the Hamilton area I pick up a mint T5 with 145,000km for $500 from Jonathan Swedish Car Repair (AKA The Volvo Shop) though the average in this area is around $600-700

[Jack Rock]

Thanks for all the info, it seems to me that from what you have written that with the right diagnostic equipment it shouldn't be too hard to get some answers from my car. I'm starting to think that I should take my car to the, gulp, dealership to at least get it diagnosed. The place I have it now is definitely competent with Volvo's as that is their specialty, I'm just not getting very prompt service, probably because I'm too easy going. Today he's going to check compression, double check for vacuum leaks and try some heavy weight oil.

I'm not upset at the thought or cost of replacing the engine - I just want this headache to be over. That being said, I don't want to throw away a decent engine.

[Jack Rock]

It PASSED! Finally. A combination of two things, first, my original Volvo cat was definitely shot which was replaced by a muffler specialist with a inadequate aftermarket cat the size of a large coffee. That was replaced with a very used Volvo cat which fixed my NOX readings immediately. Next, my Volvo specialist replaced all sensors and plugs etc with OEM parts from a donor which made no difference. He removed the EVAP line from the manifold and capped it which made it pass. We haven't gone into diagnosing what exactly is wrong but I think it could only be the purge valve. At one point early in the saga I had removed and cleaned the purge valve - it was definetly stuck open, even so, never would I think that there are enough vapours to make the car fail emissions so bad. The attachment indicates that the canister gets emptied at the appropriate time, this leads me to think that as long as all the lines and the canister itself are in good shape that only leaves the valve. I guess what I'm trying to say is, can the charcoal in the canister get saturated or can the canister become non functional?