I just recently purchased a 1996 Volvo 850 GLT Wagon. The vehicle has 167K for miles on it and I also found out that over the past 26 months the vehicle has been on the road less than 5000 total miles.

Now a couple of days later I'm getting a check engine light staying on. I went to Advanced Auto and borrowed their scan tool and it came up with a P0172 code. Bank 1 system running to rich.

Does anyone have step by step process on how to resolve this. I have a few more days before I need to have the vehicle inspected and would like to resolve this before that. What do I need to do?

Thanks.

Well, I got the car registered and inspected yesterday.
The inspection station failed the car due to a slight movement in the front passenger side wheel. He states that I need a new tie rod for it. Personally the car seems to be riding very nice and smooth. No rattles in the front end. But he states otherwise. Then he stated that a plate light was out. (Bulb ended up being loose in the socket. It was not put in all the way.)

The car passed the emissions side of things, but shortly after leaving his place the check engine light came back on.

I found the fuel pressure regulator about 6" from the Fuel Filter on the vehicle by the rear passenger wheel. The Fuel filter had to be the original unit. It was rusted solid to the strap that holds it to the bracket underneath. So I replaced that and then I looked at a couple more hoses back there and replaced them as well. After further review I may end up replacing the Fuel Pressure Regulator as well when I get some money. But if I replace the Fuel Pressure Regulator and that still does not get rid of the check engine light, What else could it possibly be?
A Volvo Person suggested that I look at the Plastic Tee under the throttle Body. He states that there is a screw on the top of the unit and it has a small o-ring that can failed from time to time. Has anyone heard of that before?

Probably in the next 500 to 600 miles I plan on doing an engine/transmission flush and switch the car over to Amsoil Synthetic Lubricants. (www.weareoil.com) At that time I plan on tearing out the air box completely, giving me room to work on the flame trap area and r/r that as well.

Then while I'm at it I might as well do a complete Tune up. Then when I get some money saved up I will replace the PCV system complete in this vehicle.

What's everyone thinking on this? Am I heading in the right direction.

Thanks.

well after about 100 miles the check engine light comes back on.

What to do next?

Running rich is caused by a cracked vacuum hose in most instances. Check all hoses that go to the intake manifold. If it has a turbo, also check the vacuum lines that go to/from that area also.

Remember, if you erase the code, you will need to drive the car to get the engine in a 'ready' state before you go to the emmissions test.

Klaus
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There is no present time, just the past and future

Is there a diagram of what hoses I should check out. I want to make sure that I do it correctly on the 96 Volvo, since it is a little different than my 95 Volvo in the engine compartment.

It is not a turbo unit at all.

Also, I did clear the code the first time and I was able to drive for almost two days then it came back. Is this what you mean by getting it in the ready mode?
Let me know. Thanks.

Mine has a vacuum diagram on the lower passenger underside of the hood, perhaps yours is there.

All the vacuum lines I can think of start off at the vacuum tree and move out. I think I had a cracked elbow at the fuel pressure regulator (on the underside of the fuel rail..)
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If you're not driving it "like its stolen," are you really driving?

Yes, it takes a couple of days for the code to store multiple times, then the CEL turns on.

Just look at all of the small hoses that come out of the manifold. Especially elbows which might be cracked. Take the cover off the throttle body and make sure the vacuum tree isn't missing any plugs.

Check the temp gage in the cluster, if it does not get warm fast, suspect and open thermostat or a bad engine coolant temp sensor.

Klaus
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There is no present time, just the past and future

Okay on this past Sunday I tracked every hose on this and replaced majority of it with new lines/connections.
On the manifold under the throttle body I had two end caps in place and replace the four other lines completely. Even replaced other hoses that where drying out as well. Then Sunday afternoon we reset/cleared the code out once again.
I ran it for just about 1 complete day and the check engine light came back on.
This time I went right after the air box area and double checked that. I put a new air filter in, sprayed some air manifold cleaner down it and this morning I replaced the Mass Air Flow Unit. Then closed everything up.
It still has the code at this point, due to the fact that I did not clear it out yet.

What to do next. I need to resolve this by Friday for the State Inspection.

Thanks.

You might want to start the engine and spray the MAF cleaner on the manifold gasket - if the rpms suddenly change, you found a leak.

Also, read the entire post:

http://www.matthewsvolvosite.com/forums/viewtopic.php?t=6283

Not all responses are correct, like replacing the O2 sensors. When an O2 sensor goes bad, there is a separate code for that.

Klaus
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There is no present time, just the past and future

Well, I have a new O2 sensor to put on the front side.
But I have been told by a person who works on Volvo that I should disconnect the battery cables to both post and put them together for about a minute. They claim that this will remove any and all codes in the computer wiping it clean. They state that after you put on another MAF Sensor that the system never really clears itself and this is the work around for it.

Has anyone got any experience or knowledge to the sort of this?

Thanks.

Touching the removed battery cables will ground any stored electricity in the computers and remove all faults - everywhere. But, you will need a long drive cycle to get the computers to learn your driving habits.

This works for MAF learning as well as auto tranny learning. The engine will 're-time' itself. This is a good thing, not something that should never be done. Just remember, these modern cars all have components that communicate with each other, and your car must re-learn to achieve what it thinks are optimum conditions to your region and driving style.

Your O2 sensor does store readings in the computer, but a couple of drive cycles will replace the old readings. Example, my wife drives an Audi A4 which turned on a CEL due to the rear O2 sensor reaching the high limit. I fixed the cracked flex pipe in front of the Cat and after 2 days, the CEL went out by itself.

Klaus
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There is no present time, just the past and future

I've disconnected the cables from the battery and that is the way it sitting currently. Just about 2 hours now.

When I head back out I will touch both cables together, hold for about a minute and then re-connect to battery.
Then I'll put a few hours ride on the car itself and see what happens.

I'm not sure if you have the same issue I did but here is what I found with my newest Volvo, a 97 850. I bought the new O2 sensor and took it with my list of things to be done by the guy who works on my Volvo's. The list of things he found was enough to make me sick (suffice it to say I did not buy well this time) but I knew I had the normal PVC issues to take care of when I bought it. He did the work and before using the O2 sensor (which he thought it wouldn't need) the CEL was cleared by the PVC replacement. Maybe it was a bad hose as some mention but check for the PVC system issues (smoking dip stick, bad ticking sounds at start up,etc) and that may be one way to fix the CEL issue. But it will be a much more labor intensive issue than some of the others. Anyway, that if my personal experience with the CEL code hopefully yours is not as big an issue.

Good luck
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1996 855 TL Platinum Ed., 1995 854 GLT 5 sp, 1995 854 (RIP), 2005 V70R (badly missed)