I have a 96 GSR in my 96 Civic. It's giving me these 2 codes right now; P0170 and P0171, need to fix it ASAP to smog the car. This is what I've changed so far; spark plugs, primary and secondary o2 sensors.

Back story; car was perfect for a while. Then I started to get a roaming idle and a CEL. Fluctuated pretty bad, I didn't know what it was. I closed my FITV all the way down and the roaming went away. CEL was still there and I was gettin' bad gas mileage... 180-200 a tank. Got it checked out, it said System too lean, BANK 1 and random misfire cylinder 1. I assumed o2 sensors- I bought (2) DENSO o2 sensors and a set of new NGK spark plugs. Misfire went away, P0170/P0171 is now here to stay.

What should I replace or look for ?
I'm going to buy carb cleaner today and shoot it around the vacuum lines see if I get any responses.

 

delete your FICV. bypass it.
try a dif main relay.
clean injectors.
try a dif octane

 

How do I delete it? I opened it up and screwed it all the way down.
Main relay..?
Cleaned the injectors.
How would a different octane help? The motor wants 91, I'm giving it 91. If say 87 does work, I wouldn't want to run a lower octane.

 

P0171 means the vehicle is running lean. It is most commonly caused by a vacuum leak - too much air sneaking in plus what's coming throught the inlet tract. It can be caused by insufficient fuel pressure, but this is very unlikely. The fuel trim code - P0170 - is probably tied to this issue as well. The unsteady idle is almost always due to vacuum leak.

In a nutshell, you either have too much air getting in (more likely), or not enought gas being injected. (very unlikely)

The first thing to do is listen to the motor running, if you're lucky, you'll hear a vacuum leak - too much air sneaking in that the computer is not accounting for. I have found hoses cracked, unhooked, throttle body gaskets torn, intake hoses cracked, bad manifold gaskets, faulty plastic intakes for those cars that have them, etc. 95% of the time you'll find air leaking in somewhere. You can use a can of something flammable to see if the idle picks up (when the spray enters the leak) but this is best performed on a cold engine. Someone with a smoke machine can pressurise the intake tract with colored smoke - this will show any leaks immediately. Your ears will probably work just fine for this, but you must listen carefully for the subtle sucking of an air leak. Try this and let us know what you find.

 

You have a lean code but the low gas mileage says you are actually running rich. In this case, you should check for an exhaust system leak near or upstream of the primary O2 sensor.

 

I used carb cleaner all around the vacuum lines according to the 96 GSR vacuum diagram, the idle never changed. Stayed the same. :-\ I sprayed that **** on every hose actually, vacuum or not.

I'll check the exhaust system leak soon! I'll keep this thing updated.

 

Oh, forgot to mention- I did a quick MAP cleaner fix and gas mileage has gotten A LOT better. Waiting for CEL to come on still, I drove about 60 miles already. No CEL, but my EVAP, CAT, o2 sensor haven't been run yet either..

 

Vehicle: 97 honda civic ex with a dx motor swapped in for a customer.

Issue:
p0170 and p0171
High Idle on initial start up
Poor gas mileage
Inconsistent performance


My findings:
(Using a scan tool ; Live data stream)HO2S readings below .3 and above .6 at 3000 rpms after the fan switched ON.
The vacuum hose on the fuel pressure regulator had a tiny tear in it. Carb cleaner didn't pick it up however it was def a nice little tear.

Action:
I replaced the hose and now no high idle when i first start the vehicle cold .
HO2S readings sweep throughout the voltage range unlike before i fixed the leak.

Result:
Much cleaner idle and power band performance.
Waiting on the gas mileage results.
Will post back to confirm resolution.

Hope this helps

 

any update on this?