1996 Volvo 850 non turbo stick. Runs a few minutes & stalls.

MrSalvage · Post by **MrSalvage** » 27 Oct 2018, 08:56

So my car starts right up and after a fews minutes warming up. The idle gets erratic then the car stalls. After that it will start and in a very rough manner and stall. Now if the car gets cold again rinse & repeat. Car has code P0455 and ran great even with that code until the weather changed just recently and became more cold. I live in Virginia so it isn't real real cold yet. I noticed the flapper in the airbox / thermostat was closed on the cold intake side so i slid a bolt into the airbox top to hold the flapper open. However that did not work at all. Same problem as before. I seen the threads for no start issues when i logged in but could not find anything similar to mine. Any ideas on where to start? Like most probable location for the leak in my emission system and my stall issues? This is a very nice website. Thanks in advance for any of your time. _Bill

Post by **erikv11** » 27 Oct 2018, 10:07

When the car is cold, it doesn't get information from the oxygen sensors to figure out how to mix fuel and air, it just does the mixing on default values. This is called "open loop." Then when it is warm it goes into "closed loop" by including information from the front oxygen sensor about the contents of the combustion exhaust gases - the information is used to set the air:fuel ratio. If the O2 sensor feedback isn't accurate, the engine gets a bad air:fuel mixture and stalls. Feedback could be inaccurate to a different amount of air than the engine air sensor (MAF) indicates, or to a faulty O2 sensor, etc.

It sounds like your car stalls when it is in closed loop, and that is usually either (a) a vacuum leak in the intake system or (2) a problem with the front oxygen sensor. Vacuum leaks are most common, you will want to look carefully at all of the rubber hoses and try spraying around suspect points with starting fluid while the car is running. Here is a good guide to vacuum lines on your car: viewtopic.php?t=65002. Do you know if the O2 sensor has ever been replaced? How is the wiring to the sensor (it sometimes get damaged)?

I definitely wouldn't just replace that sensor, do some poking around first. You could also look at closed or open loop status with a code reader, and see if the stalling coincides with the switch to closed loop. It could even be the MAF, that is easy to test especially if you have a code reader to reset codes. Unplug the MAF then start the car, see if the problem goes away. Only plug/unplug the MAF with the car off.

I would ignore the p0455 for now, until the stall is resolved.

MrSalvage · Post by **MrSalvage** » 27 Oct 2018, 10:55

Great Post! I have a folder with all the work done on the car from the previous owner. This car has 94k on it and the last owner took pretty good care of it. I guess my first stop would to be going thru all the paper work again to see if that 02 has been replaced and when maybe even some vacuum line repairs. I will also go thru the vacuum lines from the very helpful link you provided. Do you have any idea how much a cheap code reader would cost or could i build one? I will also unplug the MAF and see if i have any change. Thanks again for a wonderful post.

MrSalvage · Post by **MrSalvage** » 27 Oct 2018, 11:35

So i went thru all the records and i don't see where and 02 has been replaced. I then went out to the cold car which hasn't been started today. I unplugged the MAF and then started the car. The car did stay running for once for 10 minutes. I cut it off and restarted the car again. Well the car starts & runs now. I have concern leaving it running for too long as i have that bolt holding the flapper open in the airbox. I don't really want to break the flapper should it decide to close. The flapper is not electronic so it should work based off of the stove pipe coming from the exhaust manifold. However i don't have a stove pipe on it. I bought one and it's the wrong size. The part i bought was "Intermotor DH4" 1.75 inches in diameter i believe. Can you advise what you might do at this time? Thanks for your help! _Bill

dj_v70 · Post by **dj_v70** » 27 Oct 2018, 12:57

MrSalvage wrote: ↑27 Oct 2018, 10:55 Do you have any idea how much a cheap code reader would cost or could i build one?

You can buy a cheap Bluetooth obdII reader for under $5 on eBay. You can download app on your phone for it.

MrSalvage · Post by **MrSalvage** » 27 Oct 2018, 13:41

Thank you man for the tip! Are those cheap MAF's on eBAy any good for $20.00?

Post by **erikv11** » 27 Oct 2018, 16:59

It sounds like the MAF may be the only problem on the stalling, good news!

The air box flapper: many people permanently wedge it open with a piece of wood or something, especially in warm climates. Improves fuel economy. As you surmised it is a fairly low tech device. The stovepipe from the exhaust manifold is also completely optional. It provides heat to help the car warm up more quickly in cold weather (and bogs down mpg when it is warm). If you want to replace it, I have done it a few times with a generic one from the auto parts store but I can't be any more helpful than that, just look for one the right diameter. In the exhaust section usually.

Cheap MAF on eBay is a big no-no. The MAF has to be Bosch, the aftermarket ones simply do not work. It is expensive new but basically every Bosch MAF on these cars at the junkyard is working. Definitely a junkyard part and that's the next thing I would do. You can drive it for a couple days with the MAF unplugged, it is running rich but won't cause permanent damage running rich for a week. If you can't get to a junkyard post it up here that you need a used P80 MAF and I'm sure someone will sell you one cheap.

If it comes to it just FYI - oxygen sensor needs to be Bosch as well, with the pre-formed connector plug. And if it is super cheap for a Bosch then it is probably a counterfeit one.

MrSalvage · Post by **MrSalvage** » 28 Oct 2018, 00:07

Do the Bosch part #'s need to match? I was wondering if it matters also on the MAF if i have a manual or automatic transmission? Thanks again for the help! _Bill

Post by **erikv11** » 28 Oct 2018, 13:30

Bosch numbers will match, yes, must be 0280217107; all P80 use the same MAF after 94.

Same MAF for auto and manual, turbo and non-turbo, from 95 (850) to 98 (S/V/C70). Actually I think turbo 94 is the same MAF, too, but there are few of those left out there ...

https://www.fcpeuro.com/products/volvo- ... 0280217107

MrSalvage · Post by **MrSalvage** » 28 Oct 2018, 14:31

Perfect your a wealth of information thank you! One last question hopefully. I have a green looking corrosion on my MAF plug and socket. I was wondering what might be best to clean that with?