98 accord P0171, P0170 codes
 

Hi all,

I have a 98 accord, 4cl, 2.3 LX with 165,000+ miles

These are the symptoms

- Getting error code P0171 - system too lean (Bank1)
- Getting error code P0170 - Fuel trim Malfunction (Bank1)
- Idle is not smooth - slight hiccups now and then. Looks like it is going to stall but does not stall
- Does not accelerate smoothly at low speeds. Revs up, but lags when going up an incline
- Poor fuel economy - used to be around 28-29mpg. Now it is close to 20-21mpg (past 3 months)

What I've checked / replaced recently
- Took apart and cleaned fuel injectors yesterday
- Replaced throttle intake tube and cleaned throttle body - 3 months back
- Replaced EVAP Control valve, EVAP Canister to clear different CEL code - 3 months back
- Replaced Catalytic converter and O2 sensor to clear different CEL code - 3 months back
- Replaced Plugs and wires 6 months back

Now I'm stuck. Searched for these issues and some of them say to replace the fuel pressure regulator. Is that the next step? Should go to a shop and check for correct fuel pressure or vacuum leaks etc?

Thanks

What were the other codes? Some things might be related.

Can we assume all of the the tune up "stuff" if up to date?

In the past Honda had various publications which said it could be due to many things such as fuel injector screens may be clogged, the fuel pressure regulator needs to be replaced, etc.

See these links:

http://ww2.justanswer.com/uploads/Ho...152018_451.pdf

http://honda-tech.com/attachment.php...7&d=1255234388

However, a Honda tech said to use a genuine Honda primary O2 sensor. Denso are Honda OEM O2 sensor though. It may be that the sensor you have on your car is biased lean. Refer to this next link to read about a biased sensor.

Timely Topics -- The Vig's Oxygen Sensor

Which O2 sensor did you replace, primary or secondary? Also note that if the car is a ULEV, it uses an Air/Fuel Ratio sensor (a wide-band type sensor) as primary vs. non-ULEV primary being a regular O2 sensor.

poorman212 - The other code was P1457 for which i replaced the EVAP canister and valve. Along with it there was another code that said something was wrong with the catalytic converter. So replaced that along with the O2 sensor. Don't remember the second code.

Rest of the general maintenance is up to date - i think. air filters are relatively new. Using synthetic oil - recently changed..

redbull-1 - It is non-ULEV and the O2 sensor was a Denso one. Replaced the one that is attached to the catalytic converter. Would a non-genuine O2 sensor actually cause the rough idle and hiccup acceleration? If the O2 sensor was the cause of the problem then the acceleration etc should be fine right?

Has anyone done the re-routing of the vacuum lines explained here
http://honda-tech.com/attachment.php...7&d=1255234388

Tomorrow, I plan to check for vacuum leaks using this method (spraying carb cleaner). Will keep you guys posted on how it goes
How To Find A Vacuum Leak - YouTube

Have the codes retested to be sure these are the only ones left.

I'm thinking more of the Primary O2 or something with the evap still. Have the valves been adjusted before?

I am also leaning (no pun intended) toward primary O2 with maybe something else.

:) yes....we'll have to see if the OP comes back.....THANKS again Redbull-1

I checked for vacuum leaks as best as I could and did not find anything.

Took out the primary O2 sensor and it looked really old and rusty. Just now replaced that with a new one (denso from advance). (Thanks poorman and redbull)

Acceleration "seems" to have improved - but it's too early to say. I'm going to reset the codes and see what happens in the next few days..

Update - It is all set now. After I changed the primary O2 sensor there were hiccups but they went away after a few days. Guessing it took some time to "learn" the idle
Fuel economy is back up to 30mpg

Summary of everything I changed in the past few months
- Catalytic converter
- Primary O2 sensor
- Secondary O2 sensor
- EVAP canister
- EVAP valve
- Spark plugs
- Oil change (synthetic)
- Spark plug wires
- Cleaned throttle body
- Cleaned fuel injectors

How did you clean out your fuel injectors? I have:

P1457
P0170
P0172