Im currently working on a friends NA 96 850 wagon and it was brought in with a CEL. I checked it and the code stated bank 1 running too rich(theres only one bank so its basically running rich). He was having problems getting it started before but it seems to be starting OK. I went through and tested all of the following parts with tthe snap on Vantage or other tool that does the job
MAF
TPS
Coolant temp sensor
checked spark plug condition
Checked car/rotor condition
Now heres the issue with the 02 sensor. It seems to be working fine, but it IS giving a rich mixture signal, its putting out about 6 volts. The reason i think its ok is because watching the graph the 02 sensor responds fine to vac leaks when i make them and such.
Another thing i found when using the scantool and searchign around was that under the live data, after the car was in open loop for some time, the status changed to "Closed loop fault" under the fuel system mark. Im nor sure if this is any kind of common problem but all these parts tested out good and im having a hard time figureing out what the problem is. I am not about to go throwing money at the car without really knowing whats wrong

Thanks a lot for your help, and get back if possible

By the way, the code was cleared a couple weeks ago and it popped back up again.

 

Hello CyFi6,

Greetings from Yokohama, Japan.

It seems that you've done a logical step with a good test equipment, but please note that on rare occasions certain problems seem to appear only on Volvo tester (only the gentleman by the name of Moderator Tech can tell you more accurate info on this, though).

If the O2 sensor is triggering CEL & storing trouble code, I would double-check on the entire electrical wire(s)for the sensor (Iknow this is such a pain), and if the wires turn out OK, I wonder if you can check to verify the sensor is of OEM (Bosch). If not, the car may need a Bosch OEM sensor. In many cases, Volvos & other imports don't like to be treated with non-OEM parts. If, however, the sensor is Bosch OEM and has recently been replaced, I would remove & clean it to see if it cures the problem, though I doubt it. Also, did you check all ignition wires, including the one that connects between the coil & the cap? Judging from your thorough list, I believe you did but I wanted to make sure as I didn't see it on your list (my statement isn't very precise, is it?).Lastly, did you check the ignition coil for proper Ω?

If there is no drivability problem with that sensor, I wouldn't worry about it, unless your state/nation requires annual emissions test.

Other than the items on your list and if you don't want to spend money even on an air filter, here's what I do:

1. Check for vacuum leaks at plastic elbows/rubber lines. The elbows are known to develop cracks. Replace with new ones if cracked, or resort to the universal cure: Epoxy it[8D].

2. Take out the air filter and clean it with a vacuum cleaner.

3. Clean the throttle body with a throttle body (carburetor) cleaner that is safe for O2S & Cat. Scrub clean with a tooth brush, manually open the throttle plate and clean the inside too. Note, that after you do this, the car will be a bit difficult to start, but it only takes a bit longer for the initial combustion and eventually the engine will start. If not, floor the accelerator pedal, hold it there while cranking and release as soon as the engine fires (keepthe tooth brushas automotive use only, as such cleaners have not been proved to be effective on dental purposes[8D]). To save money, take advantage of Wal-Mart or equivalent.

4. Remove the spark plug at bank-1, clean the threads in the head & plug really good with lint-free cloth & alcohol, and swap it with a plug from different bank (clean the threads on this plug too). I know this is a pain but it's free.

5. Dump a large bottle of Techron fuel system cleaner into a half-filled tank and drive until the low fuel light turns on (keep driving near a gas/service station). Full-throttle is highly recommended during "cleaning run". This may be the largest expense (approx. US $10-12 for Techron). When done, fill up the tank with the fuel specified by the owner's manual (turbo requires 91 or higher octane).

6. If everything else fails, you have 2 options:
a. Bite the bullet and buy a new Bosch OEM sensor.
b. Put the car on sale.

This is the best I can do for now. Wait till other members jump in; they are extremely knowledgeable.

I hope this is of some use.


JPN

P.S: FYI, codes in the transmission ECU can also trigger CEL.

 

Ok, well i know the problem is that its running rich and thats the only reason the CEL is on. I can tell that the O2 sensor is wired properly because im getting a reading on the scantool inside the car of about .6 volts. I checked the filter and such for debris and it was very new looking. Im not saying im afraid to spend money on the car, but this is someones car im doing for them and im against spending money on parts that arent for sure bad. If there was a vac leak wouldnt it run lean anyways? Im going to check the coil, that is one thing i have not done, i also have not checked the timeing. I live in California, and not only is he eating up fuel, but you cannot get a smog done with the CEL illuminated. I was thinking about doing the fuel system cleaner through it in case theres something holding the injectors open possibly. I am still fairly confident that the O2 sensor is in good working shape and is accurately telling me that the engine is running rich. Is there anything else i can check before referring to the volvo dealership or changeing the 02 sensor?

Thanks again for all your help, it has gotten ideas flowing in my head. I would like to get to the bottom of it without going to the dealership as i know they can charge a hefty amount. Actually, now that i think about it i have a friend that works at a Volvo dealership, he might have a scantool that he could run for me quickly for free. Il have to talk to him and see what he says.

 

Hello again,

Ok, judging from your accurate descriptions, you are probably more skilled & knowledgeable than an average professional mechanic, including myself (I'm a professional aircraft technician and not a professional auto technician, though). Yes, a vacuum leak would generally make the engine run rich, but as you probably know, that there are cases that even the best technician in the world cannot solve, including the guys/gals who designed the engine/car. And the vacuum elbows are known to fail, so just wanted to give you one possibility to eliminate.

>but this is someones car I'm doing for them and I'm against spending money on parts that aren't for sure bad.
Excellent point, well understood. If you're in your teenage years or even in your 20's, you will have a great future as not many people are as intelligent as you are. I'm 33, and am having some mid-age moments[8D].

Anyway, let's get back to the business. So the main problem is running rich, let me see what I would do other than the things you've already covered (and this time I will not take costs into account):

1. The first place I'd look at is the air filter. I did read your reply, but air filters can look clean, while they're infested with micro-sized particles. Do you know when it was replaced last, as well as the brand name? Usually, you want to use filters made by MANN (OEM) or K&N for 850. And vacuum cleaning it wouldn't take more than 5 minutes.

2. The next step is to inspect the throttle body really well and clean it anyway. 850's throttle body is notedfor getting really dirty, due to the design of the EGR system. With enough side thrust applied to the car around curves, oil can enter around the throttle body. If the throttle body is dirty, it would restrict smooth airflow without registering in the ECU and hence the rich mixture, as you know better than I do. Also,the dirty throttle bodycould be preventing easier atomisation of fuelin the intake manifold. You may want totake the body off and do a thorough cleaning (I'll give you the $ for TB housing gasket in the end).

3. If the resistance readings on the coil is out of spec, it'll need a new one. Inform your friend that he/she should purchase OEM coil (Bosch). Make sure that the new coil comes with power stage (call). When you check the coil, check the correct Ωreadings for the ignition wires as well, if not done yet.

4.Inspect the spark plug tips under magnifying glass. I know this is an overkill, but if the plugs are of platinum/iridium, they can easily be damaged upon installation if done by someone who does not know how to handle platinum/iridium plugs. Or, you can test the plug while on the car: Use Snap-on's spark tester if you have one in your toolbox, or just remove the plug, reattach the wire and hold it with the threads touching the engine block and crank the engine while observing for a strong spark; this may be a two-men job with rubber gloves to avoid shock[:@]. But if you say the plug is ok, it probably is ok. Please note, that I'm going over some basics and am redundant, so that other people reading this thread could benefit, too.

5. As to the ignition timing, it is fully controlled by the ECU and is not adjustable, unless you can somehow access the primary ROM in the ECU to see if there's a bug, but no such problem has been reported so far.

6.Do a compression test, to see if the cylinders are gas-tight.This may not be necessary, but I just thought you would have acompression gage in your tool box andit doesn't take much time. Also, if you have a bore-scope, peep inside each cylinder.

7.Verify that there is not much back pressure due to restricted exhaust system.

8. Remove the injector(s) and have it power-cleaned.

9.Verify that the PCV system has been properly serviced/cleaned.

10. Verify that the EGR valve is not restricted and all hoses are in good condition & where they should be (often a vacuum hose from EGR valve is disconnected by the owner; not sure what kind of benefit they're expecting from it). My EGR valve, too, had a vacuum hose disconnected and plugged with a bolt, and even with this CEL never turned on (it turned on for other problem, however). The owner's manual indicates that the EGR valve cleaned at certain intervals.

11. Verify correct operation of the air pump, if so equipped.

12. Just to pass the smog inspection, as a last resort, replace engine coolant with thicker mixture (70% coolant/30% distilled water). It is scientifically proven that pure water actually dissipates heat more efficiently than the correct coolant mixture. By making the concentration thicker, the engine will run just a little bit hotter and contributes to leaner combustion. But then, as it runs hotter, the engine may produce more NOx... forget it[8D].

Well, this is the best I can do at the moment. There are about 5 more members here who have better knowledge & expertise, so if you can wait till they come in. Moderator Tech is the top dog of the entire forum.


Here's a good Volvo parts source some of us here use often (reasonable prices for OEM parts):
http://www.fcpgroton.com/volvo.htm#850
Ignition Coil: $125 (call to see if it comes with power stage)
Ignition Wire Set: $49
Throttle Housing Gasket: $0.75
Shipping charges apply, but no sales tax is required.

They're located in CT, so shipping may take a few days (when I lived in Chicago, my order used to arrive between 2-5 days).

>Actually, now that i think about it i have a friend that works at a Volvo dealership, he might have a scantool that he could run for me quickly for free.

You will be highly honored & credited by sharing your dealer tech's contact info...just kidding[8D]


I wish you become a regular member. With your skills & expertise, many people would benefit. I know it may not be worth your time or may not have the time anyway, and I myself once considered of withdrawing from here,but since this forum is one of the better places on-line and there are a few good regular members, I decided to stay as long as those people stay, even though I no longer have the car (I wish I did). People like you are not common; there was once a newbie who joined here, started posting threads like crazy and even blamed other members for not TLCing him. This guy failed to recognise thatalthough we are volunteering, we have no obligations (unless we get paid for doing this of course), and we all have our priorities (family, job, etc...) but the guy didn't seem to recognise it. I tried to help him with courtesy, but after witnessing his rudeness & immaturity, I deleted all my replies[8D].

I try tohelp people as much as I can, but I do not tolerate the following:

1. Rudeness (I admit, that I myself can be rude, as I'm against poor quality products).
2. Sarcasm (Same as above, I do apologise if my replies contain rudeness/sarcasm).
3. Lack of least common sense (wonder how hard it is to write "Thank you").
4. Unproductive argument (who's right, who's wrong, etc...).

Anyway, I wish you the best on the progress. Let us know what you find.

Also, in case if your friend's 850 develops other problems, this may be of some use:
https://volvoforums.com/m_48928/tm.htm

Sincerely,


Kanji Kotaki/JPN<script src

 

Is the Elbow on the side of the intake behind the power steering pump ok?
They are known to go bad and throw the light on.

 

Are you talking about the very small elbow that pushes onto the intake box itself?

 

No he's talking about the one on the other side. It's very hard to see and reach. It's behind the intake manifold and in front of the thermostat housing. Be careful pulling the hose off. It has a plastic tubing in it that breaks when you pull on it.