My 98 S70 isn't starting right first thing in the morning or after sitting all day. Normally it takes just a quick turn of the key and it fires right up like this: wah, wah wah, hum... Now, its more like wah, wah, wah, wah, nothing, let go of the key. Then wah, wah, wah, wah, spit, stutter, hum... Once it does start it runs perfectly. And, this only happens first thing in the morning or after it sits in the parking lot all day.

The check engine light is on. I've pulled the codes. I'm not sure which codes are helpful, or exactly how to interpret them. But, here's what it shows:

P0172 System Too Rich Bank

Oxygen Sens Mon.....INC
Oxygen Sens HTR.....OK
EGR SYS.................OK
Catalyst Mon...........INC
Htd Catalyst............N/A
Evap Sys Mon..........INC
SEC Air System........INC

MIL Ststus..............On
Misfire Monitor.........OK
Fuel System Mon......OK
Comp. Component.....OK

PTCFRZF................P0172
Fuelsys1................OL-Drive
Fuelsys2................N/A
Load Pct................1.2
ETC......................185
SHRTFTI................3.1
LONGFTI...............24.2
RPM.....................840

What does INC mean?

By the way, I recently changed the MAF Sensor. Any suggestions for where I should start looking for the issue?

 

Okay... the only actual code there is P0172, which indicates a rich fuel mixture that the ECU isn't able to correct for some reason. The rest of that info isn't relevant- the list of stuff marked "INC" and "OK" are emissions monitors which are used during e- tests. INC means "incomplete." It can't complete those checks because of the trouble code.

Now... on to the trouble code. Basically, the ECU is being told by the O2 sensor that the engine is running too rich. The ECU responds by leaning out the fuel mixture- or by trying to lean out the mixture. Once it makes all the adjustments it can possibly make, and the O2 sensor is still reporting rich, the ECU will set that code and turn on the CEL. There's several possible causes. One could be that the front O2 sensor has failed, and is constantly sending a "rich" signal to the ECU. This would cause the ECU to unknowingly lean out the fuel mixture. A lean mixture would make the car hard to start. Another possible cause is a clogged fuel filter. I know it sounds counterintuitive, but a plugged fuel filter can reduce pressure to the injectors, which will cause the fuel being sprayed into the engine to not fully vaporize. This can result in incomplete combustion, which will make the O2 sensor detect a rich running condition. Another cause could be a dirty air filter- which again could prevent easy starting. Other causes: leaking injectors, which could flood the engine. (not real likely.) Basically, there are many possible causes here, and I'd either need more information or to actually see the car (not possible!) to be able to help further. Change the above filters, clean the MAF, and see what happens. (those are all maintenance items, which is why I suggest just changing them anyways) If that doesn't help, you can check the front O2 sensor- replacement may be in order. Anyhow... best of luck. If there's any other symptoms, post that here, and I can try to help further.

 

Thanks for the response. I doubt the filters are the cause. I changed the fuel filter less then 2 months ago. And the air filter was changed about 10,000 miles ago. The car is very well maintained. The oxygen sensor is original, as are the injectors. The MAF is less than 2 weeks old, so its not dirty. I did have to send the first one back because it was causing MAF fault codes (though it did solve my stalling problem). Putting in this exchange MAF did eliminate the MAF code. But I wonder if this one is an issue too. It is a cheap generic one. To that end, I tried to test it using the procedures listed in Alldata, which are:

Checking Mass Air Flow Sensor

• Ignition on.
• Connect a voltmeter between mass air flow (MAF) sensor connector terminal 2 and 4.
• The voltmeter should read 0.1 - 0.2 Volts .

But this doesn't make sense to me. If I disconnect the connector, the MAF isn't in the circuit. So, how could this test the MAF. Am I misintepreting the test instructions? I would have thought I could test the MAF using an ohmmeter.

Is there a way to test the oxegyn sensor?

Other possible symptoms include it smells like its running rich in the morning when I start it, and it is getting poor fuel milage.

 

Okay... here's what Volvo's diagnostic flow chart gives as possible causes. This can be found on Alldata.
* Defective Mass Air Flow (MAF ) Sensor
* High fuel pressure
* Leaking injectors
* Leaking Evaporative Emission (EVAP ) System
* Contaminated engine oil
* Oil level too high
* Faulty sensor signals.

Here's what I would do. Since this happened shortly after replacing the MAF, I'd try a 3rd MAF first. The parts person is going to tell you that something else must be the cause- tell them that it's different symptoms with each one. Then, check the oil level and make sure it's not too high (I suppose a plugged PCV system MIGHT cause this problem, too...) I doubt there's an EVAP leak, as there'd be a stored code for that, too. If that doesn't do it, check fuel pressure, and check the vacuum line to the fuel pressure regulator if fuel pressure is high. Next step is going to be to check for leaking injectors. If you have a fuel pressure gauge, see if pressure drops after you switch off the key. It should remain relatively constant for 10 or so minutes. (there's specs available, I'm just too lazy to go look them up ) If you don't have a gauge, then pull the fuel rail with the injectors still attached, cycle the ignition (DON'T let the starter run- just turn the key to on then off or you'll have a heck of a mess) then observe the injectors- see if fuel drips out of them. Watch for a couple minutes. No? change the O2 sensor (front one. Should be done as maintenance every 100,000 miles anyway.)

Good luck- let us know what happens. Tech might have some other advice to give on this one.

 

The saga continues.

Its been about a month since getting Carrot's suggestion. Haven't had time to do anything. During that time its gotten progressively harder to start, and begun running rough. And, of course, the CEL remained on. Today I replaced the front O2 sensor - and the fuel pump for good measure. It seemed to start right up. But, it still seemed to run a little rough. I cleared the codes, gave it a test drive, and the CEL came back on. This time when I checked the codes I got reports of misfires on all cylinders and random misfires. These are new since I last checked it a few weeks ago. Is it possible that, because it was running rich, the issue may now be as simple as its fouled the plugs? I won't have time to get back to it for a few days or I would just throw a set in. But, meantime, I'm curious what you all may think.

 

Change the plugs... they probably are fouled.

 

Changed the plugs and no difference. The old ones were perfect:clean and dry. Changed them anyway. Running out of patience, and money. I've changed the MAF sensor, the front O2 sensor, the fuel pump and the plugs.

I pulled the codes again and I have all the same misfire codes, and the system too rich code is back.

Checked the oil level and its fine. I didn't try the MAF sensor again because it was new, and it wasn't sending a code.

 

Fuel pressure regulator?
Vacuum leak?

 

What happens when you loose one of your electonic boxes ? Don't you loose your injectors ? Ooops, I forgot, when I got past 100 K my T5 started running really rough, so I replaced the coils on each plug from a salvage yard for $ 10.00 a coil and it ran pretty good except for one plug missed at idle, so I replaced them with brand new ones and it runs very smooth ?

 

I found a vacuum leak. There's a nipple coming off the intake manifold pointing toward the back of the power steering pump. The little rubber vacuum hose/elbow connected to it was dry rotted and the end was split so it didn't stay on the nipple. Replaced the hose and it seems to run fine now. Cleared the codes and, so far, the CEL is still off.

I couldn't trace the vacuum line as it went down under the manifold. Anybody know what it connects to?

Thanks again everybody!

 

That one connects to the PCV system. It wasn't dry- rotted- it was deteriorated from oil, most likely. And if THAT is bad, I'll bet the whole PCV system is due to be changed. Drive the car until it's warm, then pull the dipstick with the engine running. Does it blow smoke? If so, your PCV system needs changed soon, before you blow a seal out.

 

Sigh. This is a never ending story. I pulled the dipstick and, sure enough, it was puffing smoke. So I'll change out the PCV related components now. The good news is its still running well and the CEL is still off.

I found the PCV components conveniently identified on IPD. Is this the best place to get them?

Thanks again for all the valuable feedback!