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Mike V.
Mike V., Technician
Category: Kia
Satisfied Customers: 25514
Experience:  I have 25 years experience working on cars. I am also a factory trained Subaru and Nissan Tech.
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P0171 p0174 fuel trims are all maxed at 25+ and short both

Customer Question

p0171 p0174 fuel trims are all maxed at 25+ long and short both banks. timing belt marks are good. fuel pressure at 40Psi. idles ok no power on accel. smoke test shows small leak at swirl valve. 4.3 gs maf at idle
JA: How many miles are on the car? Have you had the fuel pressure tested recently?
Customer: less than 50,000 but we have no history on vehicle. may have used engine
JA: What is the model/year of your Kia?
Customer: 06 kia sorento ex 3,5 auto
JA: What year is your Kia?
Customer: 06
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: i am an ase certified mechanic with 20 years in industry
JA: Anything else you think the mechanic should know?
Customer: engine vacume shows 15 or better at idle and reving so i dont suspect converters
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Kia Mechanic about your situation and then connect you two.
Submitted: 1 year ago.
Category: Kia
Expert:  Mike V. replied 1 year ago.

Hi there,

Seems like a lot of g/s coming in from the maf sensor. If you unplug it and run the car is there any improvement either with the car or the scan tool itself? Just seems like the maf sensor isn't reading right with those specs. It's hard to be 100% sure because the service manual is showing the flow in lbs of course.

Customer: replied 1 year ago.
i did unplug it. still act like pluged cat or lack of fuel. i figure g/s as 1 1/2 g per litter
Customer: replied 1 year ago.
frequency was over 1000
Expert:  Mike V. replied 1 year ago.

I am showing the maf should be about .7 lb/m at 800 rpms.

Can you tell me if the st fuel trims change at all with it unplugged?

Expert:  Mike V. replied 1 year ago.

Also, can you get it up over idle to 2k rpms long enough to get a maf sensor reading?

Customer: replied 1 year ago.
whating on scan tool to reboot
Expert:  Mike V. replied 1 year ago.

No problem. Been my experience when both banks are messed up and running lean like this, either there is a timing issue, blocked converter issue or a maf issue. Since you have eliminated the cats and the timing, AND fuel pressure, I tend to lean to the maf sensor.

Customer: replied 1 year ago.
air flow rate 1304 mv. 3.8 grams second i will switch scaners i dont know how to change the gs to lbs
Expert:  Mike V. replied 1 year ago.

Ok, I tried to google a way to do the math, but I am not sure it's accurate.

Also, if possible get a reading at about 2k rpms.

Customer: replied 1 year ago.
49 lbs is what my calculations are at idle. 1.21 lbs a min at 2000 rpms
Expert:  Mike V. replied 1 year ago.

The voltage at idle is at the bottom of the scale.

calling for 1300mV-1500mV with 1304 being so close to the bottom it makes me wonder.

Also, .7 is the min at idle on the lb/minute scale they are calling for.

I would clear the fuel trim, unplug the maf sensor and see if you can get some performance out of the engine. Even if you were to put in a new sensor, it would run off the old crappy fuel trims.

I am just saying it might be a viable test for the maf. I do think it's the problem because of it being so close to the bottom of the scale, but this test might prove it.

Customer: replied 1 year ago.
i know it is a difficult one. map sensor?
Customer: replied 1 year ago.
on old fords this use to be a map problem
Expert:  Mike V. replied 1 year ago.

I do remember that on the fords, but even the newer ones have this kind of behavior due to a bad maf sensor.

Pretty rare the map will cause this type of issue.

What is the voltage of the map at idle? I am showing it should be somewhere around 1308 mV

Customer: replied 1 year ago.
Customer: replied 1 year ago.
we are just under 3000 feet in elevation
Customer: replied 1 year ago.
2730 feet to be perfect
Expert:  Mike V. replied 1 year ago.

Monitor the "INTAKE MAP" parameter on scantool.

Possible to check these values, it does show it's off a bit according to kia

  • Specification :

    - Ignition "ON" & Engine "OFF" : Approx.1010mbar(101kPa, 14.65 psi) ~ 1040mbar(104kPa, 15.08 psi)

    - Engine "ON" : Approx.310mbar(31kPa, 4.49 psi) ~ 370mbar(37kPa, 5.37 psi)

Customer: replied 1 year ago.
3632 mv
Expert:  Mike V. replied 1 year ago.

Sorry it's not giving me a mv reading other then the one I shared with you.

It looks like ign on engine off is going to be the atmospheric pressre, then engine on and running it should switch to the other numbers. I think you should be able to see them on your scanner.

Customer: replied 1 year ago.
wy is maf showing 3.7 gram a second when its not running
Expert:  Mike V. replied 1 year ago.

lol, I do not have an answer for you, but if you unplug it and it's still showing, it would indicate a wiring issue to the maf

Expert:  Mike V. replied 1 year ago.

The service manual doesn't have any measurement for the g/s with the engine off. Sounds to me like a wiring issue at the maf though.