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P0171- Engine light on after trying to fix rough idle

  #1  
Old 02-19-2019, 09:01 AM
msg
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Default P0171- Engine light on after trying to fix rough idle

My 96 accord lx 4cyl with an Automatic transmission is having trouble after I have tried fixing a rough idle. Any help that someone can give me here would be appreciated.

Recap on everything I have done. All because there was a rough idle. First I tried re setting the idle screw, I got the idle closer to 750, but it still vibrated more than usual at idle.
  1. Disconnected the Idle Air Control Valve and cleaned it out
  2. Removed the throttle body and cleaned it out
  3. Cleaned out the Fast Idle Thermo Valve and tightened it down snug
  4. Checked the spark plugs, thats when I found oil on the plug wires
  5. Removed the valve cover and rocker assembly
  6. Replaced the o-rings
  7. Tightened back down the rocker assembly
  8. Did a valve lash adjustment
  9. Replaced the valve cover gasket and spark plug tube seals
  10. Removed and cleaned out the EGR chamber
  11. Disconnected the fuel rail and fuel injectors
  12. Cleaned and tested the fuel injectors- 2 were bad
  13. Replaced the injectors and seals rings
  14. Replaced spark plugs (NGK ZFR5F-11 2262 gapped to 1.11)
  15. Put everything back together
  16. Bleed the coolant system
  17. Cranked the car and it barely cranked and sputtered alot
  18. Finally began to run but not that much smoother at idle
  19. Drove to work this morning
  20. Engine light came on
  21. Went to Oreilly and they read the code P0171
  22. Got upset and called Auto Shops around, they are slammed til end of the week.
 

Last edited by msg; 02-27-2019 at 10:49 PM.
  #2  
Old 02-19-2019, 08:22 PM
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You have done a ton of stuff to the car. Were you getting the P0171 code before you started doing work on the car?

How long did you have the rough idle before you tried to fix it?
 
  #3  
Old 02-19-2019, 10:46 PM
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There was no engine light prior to all this. Just a rough idle and I just had to try and correct it. The rough idle began coincidentally over a month ago after I had replaced a bunch of front and rear suspension parts that had worn out and in some cases torn.

I'll be taking it in to a garage now, hate it. Wish i could have fixed it myself.
 

Last edited by msg; 02-19-2019 at 10:49 PM.
  #4  
Old 02-20-2019, 03:35 PM
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Originally Posted by msg View Post
There was no engine light prior to all this. Just a rough idle and I just had to try and correct it. The rough idle began coincidentally over a month ago after I had replaced a bunch of front and rear suspension parts that had worn out and in some cases torn.

I'll be taking it in to a garage now, hate it. Wish i could have fixed it myself.
Going thru your list, I didn't see a cap and rotor replacement. I'd try that and wires if you didn't do them. I'd do the the cap and rotor for sure as they are a wear item. I don't know what the P0171 code is.
 
  #5  
Old 02-20-2019, 07:44 PM
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P0171 is for a lean mixture. The O2 sensor is detecting too much air/oxygen. This causes engine computer to open the injectors to stay open longer to add more fuel to compensate. The P0171 is set when the engine computer gets past a certain percentage (usually 20--25%) from ideal.

Common causes are unmeasured air entering the engine, or not enough fuel getting to the engine. A misfire could also be a possibility, but you should get a misfire code as well.

If you can get a scanner that reads live data, you can watch the short and long term fuel trim at idle. I suspect it will be high in the 20s, where perfect is close to 0. Increase the engine rpm and see if the total fuel trim (short plus long term) moves. If the fuel trim decreases, then you will be looking for a vacuum leak. If the fuel trim remains the same or possibly increases, then start looking at fuel delivery.
 
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Old 02-20-2019, 08:54 PM
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Originally Posted by The Toecutter View Post
Going thru your list, I didn't see a cap and rotor replacement. I'd try that and wires if you didn't do them. I'd do the the cap and rotor for sure as they are a wear item. I don't know what the P0171 code is.
Thanks Toecutter, I probably will replace them again. 76k ago I had replaced the distributor housing, Distributor inner seal, Distributor O-Ring, Distributor Cap, Rotor Cap all Honda parts. Used NGK plugwire set RC-HE62 and NGK G Power sparkplugs. This time I sprayed carb cleaner into the plug wires to clean them out from all the oil.


Originally Posted by PAhonda View Post
P0171 is for a lean mixture. The O2 sensor is detecting too much air/oxygen. This causes engine computer to open the injectors to stay open longer to add more fuel to compensate. The P0171 is set when the engine computer gets past a certain percentage (usually 20--25%) from ideal.

Common causes are unmeasured air entering the engine, or not enough fuel getting to the engine. A misfire could also be a possibility, but you should get a misfire code as well.

If you can get a scanner that reads live data, you can watch the short and long term fuel trim at idle. I suspect it will be high in the 20s, where perfect is close to 0. Increase the engine rpm and see if the total fuel trim (short plus long term) moves. If the fuel trim decreases, then you will be looking for a vacuum leak. If the fuel trim remains the same or possibly increases, then start looking at fuel delivery.

Thanks PAHonda, Ill print out your message and share it with the mechanic tomorrow. Hopefully he can and will read. I may be buying a scanner someday soon. I really do want to learn more on how to take care of my own cars.
 
  #7  
Old 02-21-2019, 03:22 PM
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Originally Posted by PAhonda View Post
P0171 is for a lean mixture. The O2 sensor is detecting too much air/oxygen. This causes engine computer to open the injectors to stay open longer to add more fuel to compensate. The P0171 is set when the engine computer gets past a certain percentage (usually 20--25%) from ideal.

Common causes are unmeasured air entering the engine, or not enough fuel getting to the engine. A misfire could also be a possibility, but you should get a misfire code as well.

If you can get a scanner that reads live data, you can watch the short and long term fuel trim at idle. I suspect it will be high in the 20s, where perfect is close to 0. Increase the engine rpm and see if the total fuel trim (short plus long term) moves. If the fuel trim decreases, then you will be looking for a vacuum leak. If the fuel trim remains the same or possibly increases, then start looking at fuel delivery.
Thanks for the explanation. I'm wondering if the OP cleared the codes after doing all the stuff he listed, let it do a relearn, and checked the codes again, or if it's still just throwing an old code. I realize he didn't have a code originally, but you never know, it might have been right on the edge of turning one on.
 
  #8  
Old 02-21-2019, 04:33 PM
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Default Todays Update

I just picked it up and here is what I was told.
They ran a diagnostic and checked for vac leaks and he tested the fuel rates (or something like that?) and after changing the fuel filter and it cleared the code and ran a little smoother.
Some device he ran tells him the fuel mix is right now.

He said he checked the rear motor mount as well by pulling off the vacuum and it should have run better but it didnt change so that meant the rear mount was good. He said that the next thing to do was to do a valve adjustment. I had to explain how I did it to him from memory since its not a usual thing for me to mess with. I followed instructions of a different site here (sorry)
https://honda-tech.com/forums/honda-...r-f22-2477017/

He said that isnt the way he does it, something like top dead center adjust the first cyl and then do one complete rotation back to TDC and do the rest.
He suggested doing it over again, check the MAP sensor and see if the hole isnt clogged on the throttle. I actually didnt take that sensor off when I cleaned the throttle body, I just disconnected the harness to it.
He also suggested replacing the distributor and wires since its been over 70k since the last.
His assessment was its misfiring.

Cost me $173 today. I drove it around and back home and at idle its got a noticeable sputter that I guess is the misfire. If the weathers nice this weekend Ill redo the valve lash again I guess. And also start shopping for the distributor and plug wires again.
 
  #9  
Old 02-27-2019, 04:21 PM
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Default Still at it

I did a few things since last posting and it still feels off. Its had times of nearly conking out lately even.

Things I did
  1. Took off the Map sensor and checked it for a visual gunk up, but the ports look unobstructed and clean
  2. Rechecked the gaps on the new spark plugs
  3. Replaced the plug wires NGK , distributor cap and rotor with OEM
  4. Still having vibration at idle
  5. Took it to another garage and had them look it over along with a list of whats been done so far, they found no way to help
  6. Drove the next day and early in the drive it felt like it was stalling trying to conk out. Adding throttle made no difference. Pulled over and noticed the negative cable wasnt snug on the battery post..the shim got distorted. Replaced the shim that day and tightened snug
  7. Drove it a few times, still having 500 rpm at idle and vibration, and experienced the same conking out with no change when throttling and pulled over cut motor, restarted drove a few miles and have it happen again. Happened 4 times on the drive.
  8. Tried messing with the idle screw the next day, removed it and cleaned off the threads, and took a small cleaning brush and soaked the inner threaded port with carb cleaner and carefully scrubbed out any buildup then reinstalled
  9. Driving a few miles yesterday I didnt have the conk out thing happen again but I cant say its fixed, hopefully that part is
  10. The idle is still rough at 500 rpm.
 

Last edited by msg; 03-27-2019 at 08:40 AM.
  #10  
Old 03-27-2019, 08:40 AM
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Anything you guys recommend trying now?
 

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