Volvo trouble

Hi. I am the owner of a 2000 Volvo S70 SE, 2.4L no turbo. 208k km.
This morning, when I first started it, I noticed that the check engine light was on, which wasn’t the case last night.
Curious about it, I plug my obd2 scanner and the code P0172 comes up, with the indication « system too rich » below. After checking it up, it means that the air/fuel mixture in the engine contains too much gas.

The symptoms of this code listed on the website do match what I noticed on the car afterwards, which include:
- higher fuel consumption (13.6 L/100km on the information screen, instead of the habitual approximate 12.8)
- An anormal quantity of smoke coming out the exhaust (white/grey smoke thought, not black)

Since I bought it, there was always a smell of gas (outside, not inside) when I start it, I believe that there is a leak somewhere in the exhaust system. Maybe this is related to what happened this morning.

I also know that there hasn’t been any engine oil change done in (at least) the last 1.5 year. The lady I bought it from lived in the downtown of a big city and barely drove it. Also, my friend (who knows more about volvos and work as a mechanic) and I frequently checked the engine oil in the last few weeks and it always seemed perfectly fine. Because of that, I still didn’t change it.

What do you guys think I should try first? I’m thinking about checking the spark plugs first, since I read that the gas smell could be one of the many causes of this (if its not an exhaust leak) and also one of the many causes of this morning’s problem.

 

First thing I would do is clear the code(s). Then drive the car and see if the check engine light comes back. If it does read the codes and see if they are the same. If they are, I would consider a full tune up to include oil and filter change, new air filter, new fuel filter, new spark plugs, plug wires, distributor cap and rotor. Not sure if the 2000 has the coil on plug system or not but our 98 still has the distributor cap and rotor system.

Outside of that, a bad oxygen sensor can cause a too rich condition, as can a bad engine coolant temperature sensor (ECT).

The ECT is a sensor located below the thermostat and sends engine temperature information to the engine computer. When the engine is cold the computer send more fuel to the engine to aid in smooth running and faster warm up. As the engine warms up, the sensor sends the info to the computer and it will lean out the mixture as the engine warms up. If your sensor is bad and sending cold temperature info, the computer will think the engine is cold and keep sending a rich mixture. I have had two ECTs go bad over the years. One caused the dashboard temperature gauge to read warm right upon starting after sitting over night, the other time the temperature gauge never got much off the cool mark after an hour of driving. Good luck and keep us posted.

 

Thanks for your response, I didn't have much time to spend some time on my Volvo. As for my 2000, it has the coil on plug system for the spark plugs. I'll also check up the sensors that you mentioned.
I will reply to the thread when I'll have finished the tune-up!

 

light reading: https://www.matthewsvolvosite.com/vo...ation-and-fix/

As noted fuel trim issues can be a range of things... MAF, ECT, intake air leak, O2 sensor (usually these throw other codes), fuel pressure, fuel delivery.

So what to do: 1) check/clean spark plugs - mostly to tell you if one is wet fouled it may be a sticky injector or a bad coil. More often this will lead to a misfire code ie a P030x (x being the cylinder #) If need be, replace with Genuine Volvo to optimize. 2) check for intake air leaks - vacuum lines, intake air boots/tubes - spray around some carb cleaner etc, look for loose fittings/cracks etc. Also look for any signes of leaking fuel. 3) find the fuel pressure regulator - pop off the vacuum line, see if fuel drips out... (sign of a torn diaphram) 4) clean the MAF - use MAF cleaner, not carb cleaners which can be too harsh on the filament wires) 5) fill up with name brand premium. Mobil/Shell/Texaco etc - they have extra detergents that will clean the injectors etc within a tank or two. You can also throw a can of Techron in the tank as well. 5) pay attention to the temp gauge. Does it wander or creep up over time? that could be a tell for a wonky ECT sensor. 6) listen for exhaust leaks. An exhaust leak can throw off the O2 sensor, messing up the fuel trim.

 

Any update??

 

Yesterday, I checked the spark plugs (right torque, gap, general state): they're fine, I really don't believe that one of them could be the origin of the problem, neither two of my mechanic friends. Also yesterday, I started the car, rev it up a bit and listen to the engine noise: everything seems fine too, even if the check engine light is still there. The two mechanic friends mentioned previously think that the problem probably come from the MAF sensor and/or the throttle body. I bought some cleaner for both tonight and will check that probably tomorrow. After, I will try to delete the code and drive it a bit (which you told me to do first, but still didn't :/ ).

 

regarding the cleaning, use MAF cleaner not carb cleaner. Also google Xemodex to read up on common ETM (throttle body) fault symptoms. If its the ETM, they're probably the best shop to have it rebuilt.

 

Thanks for the reference!