PO171 & PO236 on 2001 Volvo S40 help

[jchrisf]

I've posted for help on the Volvo forums but no one seems to know the answer. I've always thought the people here really know their stuff and are very helpful and active so I thought I would post this here.

A couple of weeks ago my Turbo Charged 2001 Volvo S40's check engine light came on. Didn't notice anything wrong with the way the car drove but just a little issue with idle every once in a while. Took it to Autozone and the codes pulled were PO171 & PO236.

I did some research and decided to clean my MAF sensor. Once done I took it for a test drive and it was taking off like never before. Thought I had the problem fixed but tried to test a passing situation at 50 mph and the engine started surging.. it would rev then fall which would cause the car to jerk around. One time I heard a clicking sound coming from the engine. When I got to the next light it idled fine but died as soon as I let off the brake. I restarted and it drove fine while driving normally.

Did some more research and found a person with the exact same problem. He changed the MAP sensor on this intake and it cured it. I did the same but it seemed to make the problem worse. Right off it through PO171 again and PO237 this time along with an engine misfire. I started noticing problems with idle and it dying after being stopped at a light. So I swapped it with the sensor on the fuel rail and the idle and dying problem are gone but it is still surging when I try a passing scenario. I also haven't had a check engine light come on since. I have driven the car about 200 miles and still no check engine light but still having the surge. I can accelerate up through the gears sometimes with no problem and other times it will surge when it gets in the high gears. Always seems to happen when I open the throttle in higher gears but only occasionally in lower gears.

Anybody got any ideas on what to check next? I don't want to keep throughing parts at it but was thinking for changing the MAF next. I also need a good scanner that could test the sensors live if anyone has a recommendation.

 

[salv]

p0236 relates to your boost pressure sensor. the signal is either too low or too high from the sensor. check your boost pressure sensor an related connections.
p0171 is a bank 1 lean code. your o2 sensor is sensing lean fuel trims. this may be a result of many things from an evap leak on the intake to clogged or leaking fuel injectors. even burnt spark plugs. this lean condition could be a result of a boost issue with your turbo if the boost pressure sensor is not functioning.

 

[NYSteve]

Originally Posted By: jchrisf
I've posted for help on the Volvo forums but no one seems to know the answer. I've always thought the people here really know their stuff and are very helpful and active so I thought I would post this here.


Way to completely throw the Volvo Forum under the bus. People don't know the answer cause you haven't posted any updates.

You also got answers on scanner recommendations.

Back on topic.
First, what maintenance have you done?
Spark plugs, air filter, coils if nec., fuel filter etc
Areas of concern are coil packs, which can crack, and fuel pressure regulator which can get weak.

As far as your specific issue:
Do you have any boost leaks?
-There is a small hose that goes from the middle of intercooler that can crack
-How about the intercooler to throttle body hose?

As mentioned, fuel pressure regulator can be an issue. Does your car take 2-5 seconds to start? If it does this can signal fuel pressure issues. If your FPR is ok, maybe your fuel pump.

Also, the boost control solenoid is wears out. Not sure if this could be it, but a thought.

What sensor did you replace on the fuel rail?

Please post your original post here as a follow up to your thread in the Volvo Forum.

 

[jchrisf]

Thanks for the quick replies and sorry for the delay. These holiday weekends keep me busy. I have replaced the MAP sensor on the fuel rail and I have no more codes. I have made about 15 trips in the car totaling around 400 miles now and no check engine light or codes at all. I put a scanner on it yesterday morning just to see if any were there but none. The car starts perfectly, idles perfectly and drives perfectly until you try to accelerate fast. It seems that the new MAP sensor took care of the codes but the acceleration problem is still there. I replaced the spark plugs and coil packs about a year ago. It has a new air filter that is two weeks old. Fuel filter has never been replaced. It gets regular 5000 mile oil changes with Mobile 1 5w-30. I cannot see or hear any boost leaks and when accelerating hard through the first two gears the turbo kicks in fine most of the time.

 

[jchrisf]

Originally Posted By: NYSteve

Way to completely throw the Volvo Forum under the bus. People don't know the answer cause you haven't posted any updates.

You also got answers on scanner recommendations.



Hey sorry you felt like I threw the forums under the bus but didn't mean too. It's just that this forum is so much more active and I have been answering my own questions it seems over there. Here is one of my original posts on one of the forums as you asked:
http://volvoforums.com/forum/volvo-s40-11/po171-po236-52673/

 

[cutchemist42]

This might just be pointless but the P0171 code was fixed on my Mazda Protege by replacing the air intake hose since it had a tear in it.

 

[NYSteve]

Originally Posted By: jchrisf
Originally Posted By: NYSteve

Way to completely throw the Volvo Forum under the bus. People don't know the answer cause you haven't posted any updates.

You also got answers on scanner recommendations.



Hey sorry you felt like I threw the forums under the bus but didn't mean too. It's just that this forum is so much more active and I have been answering my own questions it seems over there. Here is one of my original posts on one of the forums as you asked:
http://volvoforums.com/forum/volvo-s40-11/po171-po236-52673/


Sorry, I was referring to S40Concepts. Follow up there and I think you'll have some good responses.

 

[jchrisf]

I think I have finally resolved this problem and wanted to post what I found in case someone finds this with the same or similar problem in the future. I want to thank everyone for their help. When it came down to it it was this post that was identical to my problem and sent me on my way to a resolution:

http://www.matthewsvolvosite.com/forums/...lit=fuel+filter

I think the cause of most of the confusion is that I seemed to have two different issue arise at once. The only one that coded was the MAP issues. I replaced the MAP sensor and my codes went away but the symptoms the car had did not. Incidentally there was a poster who had a similar issue and the exact same codes and he replaced the MAP sensor on the air intake by the intercooler (which Haynes actually calls the Intake Air Temperature Sensor but it is identical to the MAP sensor) however it was the MAP sensor on my intake manifold where the fuel rail is located that I had to replace.

The car ran and started perfectly with an occasional hesitation at idle but didn't happen much and was gone as soon as it started. I could not accelerate hard past 1/4 throttle or the car would start hesitating like crazy and if I keep my foot in it the check engine light would start to flash for a few seconds and then go away.

Once I read the post from the link above I decided to start concentrating on the spark plugs. I replaced them and it ran much better but still had a slight hesitation at WOT. Then I replaced the coils and spark plug wires and the problem is gone. Those codes had my attention focused on the boost and it's related sensors but when I was not getting anywhere I started thinking it was the fuel filter. I did a search on that and came to the post above which was identical and there I found my solution.