98 cl 2.3, Did fuel system cleaning around 3 weeks ago. The engine light came on yesterday. Had code read from Autozone saying:
P0171, system too lean (Bank 1)
P0172, Fuel trim malfunction (Bank 1)


Has anyone had similar experience before? What can I do to check and turn off the light?

Thanks very much for your inputs!

 

Haven't had that experience before but if they say it's bank 1 it usually means that an oxygen sensor went bad and bank 1 indicates the location of that sensor (probably up on the manifold before the cat).

 

I would check for a significant air leak into the intake manifold or throttle body.

Use throttle body cleaner sprayed at suspicious joints w/ engine idling . If a change in engine idle, you have a leak at that location.

good luck

 

Thank you for the sugesstions. I will try it out.

I remember that during the fuel system cleaning, the guy took off the vaccume line and sprayed on to throtle body to clean. Is it possible he did not tight the vaccum line enough?

Forgot to mentiont that gas mileage has dropped from 22 MPG to 14 MPG since the engine light stays on.

 

He may have tightened it, but the line may have developed a crack. Check the vacuum lines.

 

Pull the vacuum reference line to the Fuel Pressure Regulator and sniff for strong gas smell. If you smell gas, the FPR diaphragm has ruptured and gas is being pulled into the throttle body through the vacuum line. It will kill mileage.

I agree that a bad O2 sensor could cause your problem also.

There is a substantial list of possible faults for these codes in a shop manaul; Fuel Supply System, Primary O2 sensor, MAF sensor, contaminated fuel, valve clearance, intake leakage, exhaust leakage.

I would try to eliminate intake and exhaust leakage w/ careful inspection. Valve clearance is unlikely unless valves are clattering horribly. MAF sensor is a possibility, and a OBD2 scanner w/ monitoring capability would help to see if MAF output seems stable.

good luck

 

Just want to report back to you guys the results regarding my car's check engine light.

Had Honda dealer diagnose my car this morning. The technicain checked all the items suggested for code P0171: oxygen sensors, fuel pump pressure, MAF sensor, vaccune line, exhaust leakage, EGR valve, etc. Excuse me for not remembering everything. They all turn out to be fine and the problem still can not be identified.
Asked to authorize to check on injector, no clog was found in injector!
Asked to continue working on EGR ports cleaning. This time the request was declined because I have no confidence in them.

What will you guys suggest? Will Acura dealer be better?
Right now, my car drives ok except the very poor mileage (14MPG) and the CEL.

The dealer charges $215+tax for cleaning EGR ports. Is it easy to do it by myself? any recommended auto shop to do EGR ports clearing?
Are there any other possilbe problems cause my CEL and poor gas mileage

Thanks for help.

 

Come on guys. Any suggestion will be appreciated.

 

My Haynes manual says you can do a simple voltage check on the O2 sensors to see if they're in the right range regardless of whether or not you have a CEL

 

There is a long list (14 items) in my Acura TL manual (should be same for CL) for code P0171.

Your experience w/ Honda dealer indicates you need to seek better help. I would check around for best Honda/Acura service shops. This problem should not be that difficult, however it will take diagnostics to sort out the issue. How much were you charged by Honda? If substantial amount, I would go to management and complain of poor service.

P0171 is long term lean mixture detected by ECU monitoring primary O2 sensor performance. However, if the sensed mixture is false, the ECU will increase the fuel supply in an attempt to correct mixture. When long term trim limits are reached and no correction detected, the code is set. From your poor mileage, the system is not lean, but rich, however ECU thinks system is lean and keeps adding long term fuel trim.

I think you can rule out EGR system. If EGR flow was low, the system could easily compensate. I ran my 90EX for years w/ no EGR flow. All ports blocked and ECU could not detect low EGR flow. Car ran fine w/o EGR flow until I cleaned all the blocked ports to pass emissions test.

O2 sensor is a leading possibility and relatively inexpensive. A new O2 sensor can be purchased for < $100, and is easy to install w/ $5 O2 sensor socket.

Check your intake duct for leaks. Check air filter for dirt/grease. Check all vacuum lines for security (no leaks). Check for exhaust system leaks ahead of primary O2 sensor.

Lot depends on whether you intend to fix or you will seek help. If you want professional help, spend your effort seeking the best possible service you can find.

good luck

 

TexasHonda, thank you so much for such detailed suggestions.
I went to my local Acura dealer yesterday, a place full with useless people, but claimed themseves to be well-trained experts, shameless.
Here is the check list they did on my car:
0. Read code -> of course, P0171
1. check fuel pressure -> ok
2. check fuel line for restrictions -> ok
3. check spark plug, spark plug wires, cap distributor -> astonishing discovery, after market parts.
To continue diagnosis, they said I have no choice but agree to change those after-market things first for $500 around. It is totally a rip-off. I tried to talk to their idiot service manager, no help.
I had no choice but drove my car away after paying $222 for nothing.

I believe I said something bad about Honda dealer above. After my visit to Acura dealer, I realized that there is a need to take those words back . Because, they are all angles as compared to the Acura dealer.

My car still drives ok both in city and on highway except the poor gas mileage and the anonying CEL. I don't believe there is no cure for her.
Guess, I have to try and fix the probelm by myself by following you guys' suggestions and inputs. Thank you very much.

But I still have some questions:
1. My spark plug and spark plug wires are brand new non-OEM part. As for the cap distributor, it was inherited from pre-owner. Is there a connection between the cap distributor and the system too lean code P0171.
2. My friend helped me spray aroun intake vacuum line. Unfortunately and luckily, no lekeage was detected.
As for Exhaust system leak detection, I believe the exhaust is covered by a metallic hood or something. Do I need to open it?
3. I got probem with my radiator tank leakage, not severe based on coolant level. The technician at Acura guess that the gaket might already be blown. Acutally, I did not see any leak from engine cover. Is it possible?

Thank you all for your time and inputs.

 

P0171 would not be caused by spark plug wires, plugs, distributor rotor/cap.

Heat shield must be removed to inspect exhaust pipes and connections for leaks.

Radiator tanks are prone to leak around upper seam.

good luck

 

I can only find intake air temperature sensor. Where is MAF sensor located on Acura 2.3 CL?

 

Im pretty sure there isn't one on our cars.

 

Tron, thanks for your confirmation.

I got another question about oxygen sensors.
The one right after the exhaust pipe is the primary oxygen sensor,
and the other one at the downstream of catalyst converter is the secondary oxygen sensor, am I right?
With ignition off, the resistance of primary sensor was measured to be 6.9 ohms.
In contrast, the resistance of secondary oxygen sensor is equal to 10 Ohms.
Can I conclude here that the primary oxygen sensor is dead?

BTW, I can smell the gas from the exhaust pipe in the rear. I believe my car is running rich instend of lean, any comments on this?

Thank you all for your help.

 

You can't measure resistance of an O2 sensor for diagnosis. It takes a high resistance VOM to measure voltage peaks (max/min) or oscilloscope to image the voltage time trace w/ engine running. Do a google search for oxygen sensor tests. It is possible to test in place.

good luck

 

disconnect the battery for a few minutes.

the powertrain control module (pcm) idle memory needs to be reset after reconnecting the battery. To preform this, you must start the engine and hold it at 3000 rpm until the cooling fans come on. then let the engine idle for about five minutes with all accesories off and the transmission in park or neutral