Resolved 2GNT CEL P0171 Lean Bank 1

[bigdog225]

99 Eclipse GS N/T

History - Car over heated. Replaced water pump, timing belt, radiator, resurfaced the head, bought all new gaskets. Drove for 2 weeks and was sometimes dying at stops and had a rough idle. Then and the timing belt tensioner pulley bolt broke. Replaced it, replaced timing belt again. Started rigth up ran fine for about 2 miles then CEL P0171 and very rough ride and sometimes dying at stops. Very noticable smell of fuel from the exhaust which was not expierenced after the first round of fixes. All the searches I did talk about turbos. Mine is a Non Turbo. Any help is GREATLY appreciated. I am so ready to just drive and enjoy.....Thanks again

 

[BoredDSM]

Code mostly associates with your o2 sensor reading lean but if it is lean then you shouldnt be smelling gas. Clean out your maf cause it gets dirty and prevents correct readings when you use reusable filters that you spray oil on. Also an unplugged or vaccum leak can give you the P0171 code. Make sure you checked your timing. Very unlikely but you could of had the timing off and the marks on the pistons are heating up and causing pre detonation but you would most likely have bent valves already.

 

[mentalTSiAWD]

You did plug your O2 sensor in the manifold back into the harness when you reassembled everything didn't you?

 

[bigdog225]

MAF is good. 02 is plugged in. Ill check for a vacuum leak now.....

 

[link16]

Last I checked....2gnt's dont have MAF's so having a clean one might be your problem..... I would pull the spark plugs and see what color they are, otherwise I would pull and clean your o2 to make sure it is getting a good reading and not just clogged.

 

[TALONTRAX]

The 420a motor is the same as a Neon . . . The throttle body is at the end of a rubber snorkel, effectively making the rubber snorkel section part of the intake manifold, & I have seen them dry out & develop cracks leading to air/intake leaks . . . check it out . . .

 

[Project2G]

Perhaps this will help..

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[bigdog225]

Finally this thing is fixed! Replaced the Bank 1 O2 Sensor and all is good again. Went ahead and replaced the Bank 2 O2 because it had never been done. Shes runnnin great again

 

[sdsdsd]

Looking for ideas guys.

I have this code on my car appear for a few days now. I clear it and it comes back after couple days. I have not noticed any performance impacts or any issues with the car driving. I have a 2GNT 98.

Any ideas? thanks.

 

[sdsdsd]

I'm still seeing the code come and go. I've checked my o2 sensors with my scanner and it says that those are all ok.

I do get a freeze frame in the cpu and I'm not exactly sure how to read it. but one of the fuel trim values doesn't look right.

Any tips?

 

[Spln_Hrd]

MAF is good. 02 is plugged in. Ill check for a vacuum leak now.....

I doubt your maf sensor is good on a n/t your car uses a speed density system which uses a manifold absolute pressure sensor and a throttle posistion sensor to calculate airflow.


to sdsdsd:

If you have access to a scan tool look at your long term fuel trim with the car idling for a few minutes and see if it goes above 10%. Do this cold and hot.

Then with the engine warmed up run the engine at about 2500 rpms for 5 minutes and see what the fuel trims are doing is they normalize you more than likely have a vacuum leak, because vacuum leaks ofset the airflow alot more at low loads.

After you have done this mash your gas pedal to the floor and release it immediatly, after the release your o2 sensors should both read high. That is a good indication that they are working properly.

 

[sdsdsd]

My scan tool won't show me live readings. Its an Actron cp9175 i think is the model number. I can see what the fuel trim is through at the time that the code was thrown because it creates a freeze frame.
Per the sensors it shows that the o2 sensors are both ok. I'm thinking its prob a vacuum leak and those I know are a pain to find

I'll keep you posted. thanks for helping!

 

[sdsdsd]

Finally did some scanning in my car since i didnt drive it for a bit.

Some of the stuff i pulled with my scanner from the freeze-frame the code was tossed at:

Engine RPM: 832
Load Value : 4.7%
MAP Sensor: 43KPA
Coolant temp: 163 degrees Fahr
Long Term Fuel Trim 1 : 24.2 %
Short Term Fuel Trim 1: -100.6%
Fuel System 1: CLSD
Fuel System 2: N/A %
Vehicle speed: 0 MPH

I'm not sure how to interpret this info. Does anyone with more experience know more about how to interpret the code?

Funny thing is when i clear the scanner it is random how quickly it comes up.

thanks.

bump

 

[cgmtboarder]

i have a 95 eclipse n/t and it has been doing the exact same thing as the OP. rough idle and acts like it wants to die and it sputters alot. and finally after 4 months i got the check engine P0171. so im gonna change the bank 1 o2 sensor and hopefully that fixes it.

 

[Project2G]

i have a 95 eclipse n/t and it has been doing the exact same thing as the OP. rough idle and acts like it wants to die and it sputters alot. and finally after 4 months i got the check engine P0171. so im gonna change the bank 1 o2 sensor and hopefully that fixes it.

This may help.

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[AM2SS]

Finally this thing is fixed! Replaced the Bank 1 O2 Sensor and all is good again. Went ahead and replaced the Bank 2 O2 because it had never been done. Shes runnnin great again

Did your car have hesitation before you changed out your O2 sensor? I'm having a similar issue with my 99 Eclipse GS.

 

[BLACK'98DSM]

That member has not been active since '08.

I thought in another thread that you listed the O2 sensor as being replaced. If not, you should test it.

 

[AM2SS]

I thought in another thread that you listed the O2 sensor as being replaced. If not, you should test it.

I replaced the front or first sensor, I didn't replace or test the downstream one, on a OBD2 scanner it looks good. Just at a loss. If I baby the car it runs well but if I want to floor it she boggs down and I have to ease up on the peddle to get her going? I know eventually she'll run great just getting my ass kicked.

Any suggestions?

Oh and another thing that might help in the morning or when the car's been sitting for a hot minute I have to rock the key back and forth and listen to the fuel pump prime four times and she'll pop right off every time if not I have to play with it for a hot minute to get it to crank.

 

[BLACK'98DSM]

Don't worry about the rear O2 sensor for now. I call it a sniffer. It's only there to sniff out excess emissions, typically from a faulty convertor. It won't actually effect the air or fuel demands/delivery.

Those are definitely the symptoms of a lean condition. You aren't getting the code from a faulty sensor, but because the readings are truly lean.

I know you verified fuel pressure but I don't recall the result or what your method of testing was. Did you check pressure after sitting for a while? What about during WOT? It sounds like the fuel pump is problematic, assuming there are no restrictions post-pump. Often times a weak and failing fuel pump can support idle speeds and low load. But will back drain over time and won't deliver under heavy load.

 

[AM2SS]

Don't worry about the rear O2 sensor for now. I call it a sniffer. It's only there to sniff out excess emissions, typically from a faulty convertor. It won't actually effect the air or fuel demands/delivery.

Those are definitely the symptoms of a lean condition. You aren't getting the code from a faulty sensor, but because the readings are truly lean.

I know you verified fuel pressure but I don't recall the result or what your method of testing was. Did you check pressure after sitting for a while? What about during WOT? It sounds like the fuel pump is problematic, assuming there are no restrictions post-pump. Often times a weak and failing fuel pump can support idle speeds and low load. But will back drain over time and won't deliver under heavy load.

I used a fuel pressure gauge to take readings, 48-50 lbs while running. It slowly lost pressure when I shut off the engine. After a few hours it's 0, it has a brand new fuel pump I just put in along with a new fuel filter and fuel pressure regulator. Another issue is it takes forever to fill the fuel tank. I looked at a vacuum diagram and it looks like the vacuum and EVAP system is connected. Could these issues be linked?

 

[BLACK'98DSM]

It shouldn't reach zero pressure after just a few hours. A healthy fuel system will hold pressure for weeks - sometimes months. I let one of my 2g's sit for 6 months and when I disconnected the fuel rail it sprayed everywhere. That means you have a leak. Whether it's internal or external needs to be determined. If you can verify that there are no external leaks, fuel is draining back to the tank. Which is normally a faulty fuel pump. Unfortunately new doesn't always mean good.

 

[AM2SS]

It shouldn't reach zero pressure after just a few hours. A healthy fuel system will hold pressure for weeks - sometimes months. I let one of my 2g's sit for 6 months and when I disconnected the fuel rail it sprayed everywhere. That means you have a leak. Whether it's internal or external needs to be determined. If you can verify that there are no external leaks, fuel is draining back to the tank. Which is normally a faulty fuel pump. Unfortunately new doesn't always mean good.

Question when I install the new fuel pump my book told me I did not need to put a sealant or caulk or group or anything on it I cleaned the mating surface really well I had a brand new gasket I put it on should I have used a sealant? I'm asking this question because the first 24 maybe 36 hours I had the brand new fuel pump in it ran like a top and the check engine light went out and now it's back to the way it was hesitation and fuel leaking down within 5 lbs a minute.

 

[AM2SS]

I used a fuel pressure gauge to take readings, 48-50 lbs while running. It slowly lost pressure when I shut off the engine. After a few hours it's 0, it has a brand new fuel pump I just put in along with a new fuel filter and fuel pressure regulator. Another issue is it takes forever to fill the fuel tank. I looked at a vacuum diagram and it looks like the vacuum and EVAP system is connected. Could these issues be linked?

Well I replaced my fuel pump about two three weeks ago it's running better I don't have to sit there and prime it the four or five times, most the time she fires right off. If I drive it normal it's good if I floor it she falls on her face. It passed the smoke test but it still takes forever to put fuel in this thing. so evap valves?