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Tim Mohr
Tim Mohr, ASE MASTER TECH
Category: Ford
Satisfied Customers: 15121
Experience:  30 YRS EXPERIENCE, FOREIGN AND DOMESTIC, GAS AND DEISEL
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Name is ***** *****. Have a 2005 Freestar 3.9. Has code

Customer Question

Customer: Name is ***** *****. Have a 2005 Freestar 3.9. Has code p0175. I have a scanner and get you any info needed. Vehicle recently had stuck secondary runners, replaced lower intake. The p0175 was there when the code for the secondary runner code was present, thought it might fix both, but only fixed the one problem. Cleaned MAF, checked all hoses/sprayed intake with carb spray. No change in rpm. EGR is clean and holds vacuum.
JA: Thanks. Can you give me any more details about your issue?
Customer: Has code p0175.. No other issues
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Submitted: 11 months ago.
Category: Ford
Expert:  Tim Mohr replied 11 months ago.

Hi, my name is ***** ***** your scanner what are the LFT readings, on both banks?

Customer: replied 11 months ago.
LTFTb1 is 5%
LTFTb2 is -10%
Expert:  Tim Mohr replied 11 months ago.

ok, then this is isolated to the bank 2, can you pull the plugson bank 2 and see if all 3 are wet or sooty, or is 2 good and only 1 wet or sooty?

Expert:  Tim Mohr replied 11 months ago.

are you still here???

Customer: replied 11 months ago.
4/5/6 all look normal. No wetness. Nothing discernable. Electrodes are reasonably clean.
Customer: replied 11 months ago.
All have a little bit of black.
Expert:  Tim Mohr replied 11 months ago.

ok, then you either have a bad MAF sensor, or the that bank exhaust has a restriction in it, the did you just clean the MAF or did you replace it?

Customer: replied 11 months ago.
Cleaned it only.
Customer: replied 11 months ago.
Why wouldn't a bad MAF affect both banks though?
Expert:  Tim Mohr replied 11 months ago.

Usually it will effect both banks, but we have seen where the bank 2 runs rich also when they are bad, I would first have a exhaust back pressure test done on that bank, how many miles do you have on this?

Customer: replied 11 months ago.
217k
Expert:  Tim Mohr replied 11 months ago.

then it is most likely a partially plugged cat on that bank, with that mileage, an exhaust backpressure test will verify this, the back pressure must not be higher than 1 psi at idle, if it is, then the cat is partially plugged,Tim

Customer: replied 11 months ago.
After a long wait for a backpressure tester, there is less than 1psi backpressure. What is the testing procedure for the MAF?
Expert:  Tim Mohr replied 11 months ago.

the maf is checked with a scanner to read the airflow when idling

Customer: replied 11 months ago.
That's not much help. What are good parameters?
Expert:  Tim Mohr replied 11 months ago.

at idle it should be around 5 grams a second, depending on your altitude,Tim

Customer: replied 11 months ago.
4.98-5.8 @ idle..800 above sea level
Expert:  Tim Mohr replied 11 months ago.

then that test good, you m ight have a bad injector on that bank, if one sticks open, it can cause the whole bank to read rich, can you monitor the short term fuel trim, and then disconnect each injector, one by one, and see if 2 of them change the short term fuel trim, and one does not, if so, then the injector that did not change will be the culprit,Tim

Customer: replied 11 months ago.
With injectors all connected, ST is around -10.. it goes up to +14-17 with the outer 2 disconnected (1 at a time). Center one jumps to +44 when unplugged.
Expert:  Tim Mohr replied 11 months ago.

then it sounds like the outer 2 are the culprits,Tim

Customer: replied 11 months ago.
But the rear ones do the same..
Expert:  Tim Mohr replied 11 months ago.

???? they should each drop it equally?

Customer: replied 11 months ago.
The rears take the bank 1 stft to around 18. The front outer two take the bank 2 stft to 17 or so. The middle takes it to 44.
Customer: replied 11 months ago.
What should they be at?
Expert:  Tim Mohr replied 11 months ago.

ok, the bank 2 middle takes to 44? is this a positive or negative?

Customer: replied 11 months ago.
Positive 44. The rest are 16-19 positive
Expert:  Tim Mohr replied 11 months ago.

ok, then my mistake, the center is the bad injector,Tim

Customer: replied 11 months ago.
Should I test it or assume it's bad?
Expert:  Tim Mohr replied 11 months ago.

the easiest way to verify this, is to swap it with the enter one on the other side, and clear the codes, and see if the code come =s back a bank 1 rich code, if it does, then you know the injector is bad,Tim

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