Check Engine Light 2003 Ford Focus, 174k miles

[RobbS]

2003 Ford Focus, 174k miles. Last week I ran into a highway shutdown, stop and go for 45 minutes, my check engine light came on. The first opportunity I had to stop, I did.The car ran fine, runs perfect.
I scanned the car and had two codes. One for lean bank 1 PO171, and catylist converter PO420. I cleared the codes and carried on. Car runs great, as normal.
I put a bottle of REDLINE in the tank with some Exxon 93 octane.
Anyone experienced the same codes prior to something obvious bad to happen?
Anything to look for?
Thanks

 

[SC Maintenance]

One for lean bank 1 PO171

This means it either is 25% lean or it thinks it is. So its adding 25% more fuel than design currently. You won't get a lean CEL until its at 25%.

So if its really that lean its likely a vacuum leak, or just a dirty MAF sensor. I would start by cleaning that.

If its not really that lean then your adding a lot of extra fuel which can cause problems later.

Is this a 4cylinder or V6?

 

[RobbS]

This means it either is 25% lean or it thinks it is. So its adding 25% more fuel than design currently. You won't get a lean CEL until its at 25%.

So if its really that lean its likely a vacuum leak, or just a dirty MAF sensor. I would start by cleaning that.

If its not really that lean then your adding a lot of extra fuel which can cause problems later.

Is this a 4cylinder or V6?

Thanks, I have the 2.oL 4 cylinder. I do have MAF Sensor cleaner. I'll do that right away, easy enough. Thanks

 

[slacktide_bitog]

Is the car loud? Do you suspect an exhaust leak?

Thanks, I have the 2.oL 4 cylinder. I do have MAF Sensor cleaner. I'll do that right away, easy enough. Thanks

Both Focus engines are 2.0L (the Zetec and SPI)

 

[xspeedy]

Do you have a scanner that can provide you with live fuel trims?

 

[RobbS]

Is the car loud? Do you suspect an exhaust leak?




Both Focus engines are 2.0L (the Zetec and SPI)

Zetec engine. I DO have a new, slight exhaust leak. I can hear it, sounds like it's under the driver's side. Slight

 

[RobbS]

Do you have a scanner that can provide you with live fuel trims?

I have a really old hand held unit. Not sure if it can trend logs

 

[slacktide_bitog]

Zetec engine. I DO have a new, slight exhaust leak. I can hear it, sounds like it's under the driver's side. Slight

The leak could be between one of the oxygen sensors and the catalytic converter. If the exhaust leak is before the last oxygen sensor, that is likely the cause of the codes. If the leak is way after the cat, near the muffler or tail pipe or something, then it's not the reason for the code.

 

[RobbS]

The leak could be between one of the oxygen sensors and the catalytic converter. If the exhaust leak is before the last oxygen sensor, that is likely the cause of the codes. If the leak is way after the cat, near the muffler or tail pipe or something, then it's not the reason for the code.

Thank you
I will have it repaired ASAP
THNX AGAIN

 

[97prizm]

2003 Ford Focus, 174k miles. Last week I ran into a highway shutdown, stop and go for 45 minutes, my check engine light came on. The first opportunity I had to stop, I did.The car ran fine, runs perfect.
I scanned the car and had two codes. One for lean bank 1 PO171, and catylist converter PO420. I cleared the codes and carried on. Car runs great, as normal.
I put a bottle of REDLINE in the tank with some Exxon 93 octane.
Anyone experienced the same codes prior to something obvious bad to happen?
Anything to look for?
Thanks

Does it ever occasionally have a tick or slight hiccup at idle? Have the codes come back?

 

[RobbS]

Does it ever occasionally have a tick or slight hiccup at idle? Have the codes come back?

Thanks,
No it has no ticks or hickups at idle.Runs perfect and a couple hundred miles later the codes never showed up

 

[hemitom]

By any chance did a prior fill up contain a higher dose of Ethanol ? IE 15% blended fuel.
Or you possibly got fuel with a higher dose than it should have been at the pump.

 

[RobbS]

By any chance did a prior fill up contain a higher dose of Ethanol ? IE 15% blended fuel.
Or you possibly got fuel with a higher dose than it should have been at the pump.

Hi
I've filled up at the same EXXON every time. No change in fuel at all.
I just added a bottle of REDLINE and filled with 93 octane. It may be physiological but it starts and drives with more pep and smoother. That was yesterday morning.
Thanks