Hesitation & Surge - Check Engine Light On - Code P0171

Cafe Racer

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Buick Encore & Buick Enclave
Thread starter #1
I'm a new member and desperate for an answer to my wifes Encore problem. It's a 2015 and a few months ago it began to surge and hesitate when coming to a stop and when stopped. The check engine light came on and she's getting poor MPG and strangely the car won't start after stopping and refueling. It needs to sit for a few minutes before it will start. We took it to our local mechanic who said the check engine code was P0171, a lean fuel trim. He cleared the code and checked for air leaks and said the car needed a new PCV valve and he installed one. He said the fuel trim was okay. Car ran fine for a few days and then the check engine light comes back on, same symptoms. Called our mechanic again and he recommended that we take it to the dealer as they would have more experience with this. Wife made an appt at the Buick dealership. They read and cleared the code, P0171. They said everything checked out okay and after paying some big bucks for them to clear the code, the check engine light came back on later that day. I went ahead and cleaned the mass air flow sensor with some special MAF cleaner. That didn't change anything. I told the wife to dump the car since the dealership is no help and absolutely no support and the both of us feel they are untrustworthy. She said she's going to drive it until it breaks then the dealership should be able to fix it then. Currently, the check engine light comes on then goes off then comes on, etc. Never know when it will be on or off, the car still surges while coming to and sitting at a stop sign. Wondering if anyone here has experienced this and their dealership actually made an effort and diagnosed the problem and had it fixed. My wife loved the car when she first got it but now she hates it and is afraid it will leave her sitting. I'd appreciate any help and don't want to start willy nilly replacing parts and throwing money at it. I apologize if the post sounds dreadful towards the Buick dealership but they really gave my wife the brush-off (that's putting it nicely). Thanks
 

HotZ28

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1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU
#2
I apologize if the post sounds dreadful towards the Buick dealership but they really gave my wife the brush-off (that's putting it nicely). Thanks
That is the typical GM service Manager/Technician to female complaints!! They think they are all idiots! Do you still have a warranty? How may miles on the vehicle? PO171 is very difficult to diagnose, there are about 15 different possibilities of the problem. I would leave the vehicle at there location until the problem is resolved. Som Tin Wong with the whole vehicle diagnostics & the dealership should resolve if they are capable!!
 
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Cafe Racer

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Buick Encore & Buick Enclave
Thread starter #4
The warranty has long been over. She just turned over 80,000 miles. I love the idea of leaving the car at the dealership, however the closest one to us is an hour away. That makes it difficult to leave the car there, especially given she uses the car for work and puts more miles on than the average person. But I wouldn't be comfortable leaving it with the non-professional people at this dealership. We'll have to try to find another one that we can leave it at. A comment about the warranty, many many months ago, there was some unknown fluid on the garage floor under her car. Car obviously had a leak somewhere. We took it to our local mechanic and he diagnosed the problem as a leaking turbo hose. He said to check with Buick to see if it was covered under warranty. That day she went to the dealership to see if it was covered and while she was doing that, I was home calling Buick. Can't remember who I called, but it wasn't a dealership. Of course the dealership said it was not covered under warranty and gave her an estimate of $900 to fix it. Luckily, while she was still at the dealership, I called with with the news I received which was it was covered under warranty. I specifically asked the person I spoke to what we should tell the dealership when they refuse to honor the warranty. She gave me some complaint account number and told me to have the dealership call Buick, if they refuse I was to call her back. My wife went back in and gave them the info and about 30 minutes later, she had an appointment for it to be repaired under warranty. No apology given just a ton of attitude. I don't think my wife will enter a dealership service area again. These are the reasons why I loath this Buick dealership. They treat people poorly and overcharge for everything. I don't mind paying for their service if they give service. Our mechanic said if it wasn't covered under warranty, we'd be looking at a $250 bill for him to repair. Never had a problem with the foreign dealerships I've been to but then again, the three foreign cars I've owned didn't go to the dealership very often.

I know there are a lot of things that cause this problem, I was hoping someone else had a similar issue and how they fixed it. Like I said, we don't want to throw money at it replacing parts unnecessarily. Thanks for the reply, I think I'll try to talk my wife into letting it at another dealership and allow them to explore the problem. Funny thing, I inspect dealerships here in PA and I think we'll take it to the dealership in the area I inspect. I'll talk to the owner first and let him know we'll be bringing the car in and what our expectations are. That "may" help or maybe not. Because of this one crappy dealership, I now have a negative attitude about all Buick dealerships. But I don't have a choice, I'm at their mercy....until we unload it and say goodbye to Buick. In reality, that may be the only answer. Dang shame, she really liked the car before this issue.
______________________________
 

MelsRegal

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#5
Below are possible causes

Did anybody check the fuel pressure?
Did you try a bottle of fuel injector cleaner?
might be worth trying a O2 sensor replacement.

•The MAF (Mass Air Flow) Sensor is dirty or faulty
Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor
•Possible cracked vacuum or PCV line/connection
•Faulty or stuck open PCV valve
•Failed or faulty oxygen sensor (bank 1, sensor 1)
•Sticking/plugged or failed fuel injector
•Low fuel pressure (possible plugged/dirty fuel filter!)
•Exhaust leak between engine and first oxygen sensor
 

ldog2003

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Mount Pleasant, Michigan
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2013 Buick Encore
#6
Sounds like the same thing mine was doing when I had a PCV failure.
It is apparently extremely common on these 1.4 engines.
It is hard to be entirely sure but I would say a PCV failure is very likely the problem.

Take off the plastic cover on the engine. On the right hand side of the valve cover there is a round plastic piece that is your PCV valve
There is a small portion that sticks up. With your engine running touch this sticking up piece. if you feel or hear vacuum you have a bad PCV valve.

This video will help.
https://www.youtube.com/watch?v=vogDBhnl6Rs

The solution to this problem is to replace the entire valve cover. There is also a hose which may or may not need replaced.
My local shop charged me about $300 for the job including parts.

Also its probably better they gave her the bush-off than trying to tell her she needed $3K in engine work like they did to me
 
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TheAirman

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Buick Ownership
2013 Encore Premium
#7
Re: Hesitation & Surge - Check Engine Light On - Code P0171

This thread is an example of why I'll probably never buy another GM vehicle. From their zoot suit wearing salesmen, to their thieving service departments. Nothing changed in 30 years.

P0171, according to the manual, is a "Fuel System Lean" diagnostic trouble code. In other words, the engine computer, through the O2 sensor and MAF sensor (mass air flow) adjust your fuel mixture just like a carburetor used to in the "olden days".

Causes:
MAF sensor
Aftermarket intake or air filter
Bad exhaust system
Vacuum leak
Low fuel pressure
Bad EVAP sensor or system
Bad crankcase vent system

But then again the grease monkeys in your "Factory certified GM Service center" should know that. But they don't.

Good luck. You'll need it.

- - - Updated - - -

Below are possible causes

Did anybody check the fuel pressure?
Did you try a bottle of fuel injector cleaner?
might be worth trying a O2 sensor replacement.

•The MAF (Mass Air Flow) Sensor is dirty or faulty
Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
•There could be a vacuum leak downstream of the MAF sensor
•Possible cracked vacuum or PCV line/connection
•Faulty or stuck open PCV valve
•Failed or faulty oxygen sensor (bank 1, sensor 1)
•Sticking/plugged or failed fuel injector
•Low fuel pressure (possible plugged/dirty fuel filter!)
•Exhaust leak between engine and first oxygen sensor
Great Post !!! Good job.

Didn't think of the oiled filter.
 
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