code 171 & 174

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Sep 5, 2007 | 10:58 AM

Primetime1

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From: Great Falls, MT

code 171 & 174

Hey guys, My cousin has a 97 F150 with a 4.6 & approx 110k miles. He is getting an engine light, so I read the codes for him & got 174 & 171. They read system too lean on bank 1 & bank 2. We replaced the fuel filter and ran some sea foam through it. Filter was very bad. He is still getting the code though. I'm curious what things would throw that code - O2 sensor?? Any help is much appreciated.

Sep 5, 2007 | 11:49 AM

Bluegrass 7

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Would you believe there is an air leak somewhere from the air meter on to the intake manifold.
Look at all the attaching hoses, pcv valve etc.
The codes are the results of the computer shifting the fuel too 'rich' trying to correct for excess unaccounted for air..

Sep 5, 2007 | 12:04 PM

Silver Streak

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From: Broken Arrow, OK

It's either a vacuum leak or a dirty MAF.

Sep 7, 2007 | 12:14 AM

03-F150

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From: Boston, MA

I would try the MAF. My '03 4.6L had the 171 and 174 codes. I bought a security-bit set so I could remove the control module to be able to clean the delicate wires. Sprayed it with a little carb cleaner and cleaned with a Q-Tip. CEL has not come back on. It's been 3-4 weeks.

BTW, I have an aftermarket air kit and cleaning and re-oiling the filter can cause this problem. Too much oil on filter will dirty MAF.

Sep 7, 2007 | 12:20 AM

loony2000

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I don't think it would be the o2 sensor. Isn't there a separate code for that?

Sep 7, 2007 | 10:36 AM

Primetime1

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From: Great Falls, MT

Thanks guys! I'm going to check it out this weekend, possibly even this afternoon with him. I was thinking about vacuum, so I'll look at those lines pretty closely. Cleaning the MAF is easy, so I'll do that just as a precaution. I know he doesn't have a K&N filter on it, so it wouldn't be overoiling that. I know O2 sensors have their own codes, but have "heard" they can cause stuff like this. He hasn't noticed any drivability issues with it. He still has normal power and mileage, but doesn't want to pull his camper out of the mountains with it and cause more issues. We may just need to grab it with my superduty, but I want to help him out with it anyway. I'll let you know the progress. If anybody thinks of anything else, feel free to let me know.

Sep 7, 2007 | 11:22 AM

Silver Streak

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From: Broken Arrow, OK

I've never seen an O2 sensor set a 171 or 174. There are codes for O2 inactivity and lack of switching that will trip well before the system lean parameters are met.