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I have a 97 Contour,6 cyl,manual.150,000 miles. Both O2 sensors were replaced in 2/04. CEL came on shortly after they were replaced. My mechanic got codes P0171 and P0174 and states sensors need to be replaced. Any suggestions?Thanks.
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i beleive if you get the codes saying that both banks are slow to switch then you need to clean you maf as if is throwing things off and the O2 sensors are fine
- 95 Mystique LS - Zetec/5spd
- 99 Contour SeVT Sport - Duratec/5spd
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Your mechanic is wrong. I search would have got hundreds of results. PO171, PO174 at the same time means there is a vacuum or intake leak, a very less likely chance it can be your fuel pressure regulator.
To check for intake manifold leaks, using starting fluid with the car running at idle spray around the gaskets, if the engine stumbles there is your leak and that is what is causing the code.
If no leaks are found that way, use carb cleaner spray your vacuum lines with the car running at idle, if the engine stumblee there is your leak.
Honesty I would find a new mechanic, any mechanic who didnt grab the code book or use the Ford CD to see what causes those codes is a bad mechanic.
Good luck.
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What this means is that your Mass Airflow Sensor may have become contaminated. Rather than replacing the MAF as Ford recommends, I have always successfully cleaned MAFs with carb cleaner. If this doesn't work I guess you could always change the fuel filter... 
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Originally posted by TronX:
What this means is that your Mass Airflow Sensor may have become contaminated. Rather than replacing the MAF as Ford recommends, I have always successfully cleaned MAFs with carb cleaner. If this doesn't work I guess you could always change the fuel filter...
WTH are you talking about, a CEL because of a fuel filter? Also if the MAF was dirty he would get PO171 system to bank 1, ONLY, he wouldnt get PO174 as well.
To the first poster ignore that post by TronX, he has no idea what is talking about.
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Originally posted by HITMANinMI:
Originally posted by TronX:
What this means is that your Mass Airflow Sensor may have become contaminated. Rather than replacing the MAF as Ford recommends, I have always successfully cleaned MAFs with carb cleaner. If this doesn't work I guess you could always change the fuel filter...
WTH are you talking about, a CEL because of a fuel filter? Also if the MAF was dirty he would get PO171 system to bank 1, ONLY, he wouldnt get PO174 as well.
To the first poster ignore that post by TronX, he has no idea what is talking about.
You think you know everything about cars? The CEL codes do not always tell you what�s really wrong and it can mean many things depending on the maker of the car. The fuel filter its self would not set off a CEL code here, but this was more of a suggestion for fixing related issues. Besides it can help if its never been replaced from years of driving. Along with a few others I can think of like replacing any damaged PCV valves, Inspect each vacuum line for leaks/cracks, clean or replace any air filters, Reseat the oil dipstick and checked the gas cap.. LOL 
There is a TSB from Ford.
Article No.: 98-23-10
Date: 11/23/98
Mass Air Flow (MAF) - Sensor Contamination
P0171, P0174 (Fuel system lean, Bank 1 or 2)
There is no procedure for cleaning the MAF; Ford says it has to be replaced.
All though you can clean this part as many here have already done. This same part can also give you many other codes...It's a real Ford Gem. 
He should inspect the hose from the PCV valve to the intake.
Sometimes the lower intake leaks at the IMRC seals� (This can cost a lot of money to fix.)
Though it is possible you may only need to clean the EGR ports thoroughly.
The PCM might also be defective ect�?
And if he comes back saying I was right about any of this then I'll be sure to step all over your ego trip. 
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Originally posted by TronX:
Originally posted by HITMANinMI:
Originally posted by TronX:
What this means is that your Mass Airflow Sensor may have become contaminated. Rather than replacing the MAF as Ford recommends, I have always successfully cleaned MAFs with carb cleaner. If this doesn't work I guess you could always change the fuel filter...
WTH are you talking about, a CEL because of a fuel filter? Also if the MAF was dirty he would get PO171 system to bank 1, ONLY, he wouldnt get PO174 as well.
To the first poster ignore that post by TronX, he has no idea what is talking about.
You think you know everything about cars? The CEL codes do not always tell you what�s really wrong and it can mean many things depending on the maker of the car. The fuel filter its self would not set off a CEL code here, but this was more of a suggestion for fixing related issues. Besides it can help if its never been replaced from years of driving. Along with a few others I can think of like replacing any damaged PCV valves, Inspect each vacuum line for leaks/cracks, clean or replace any air filters, Reseat the oil dipstick and checked the gas cap.. LOL
There is a TSB from Ford.
Article No.: 98-23-10
Date: 11/23/98
Mass Air Flow (MAF) - Sensor Contamination
P0171, P0174 (Fuel system lean, Bank 1 or 2)
There is no procedure for cleaning the MAF; Ford says it has to be replaced.
All though you can clean this part as many here have already done. This same part can also give you many other codes...It's a real Ford Gem.
He should inspect the hose from the PCV valve to the intake.
Sometimes the lower intake leaks at the IMRC seals� (This can cost a lot of money to fix.)
Though it is possible you may only need to clean the EGR ports thoroughly.
The PCM might also be defective ect�?
And if he comes back saying I was right about any of this then I'll be sure to step all over your ego trip.
First off no I admit I dont know alot about cars, most of what I know I learned here and the other part at school.
Secondly when you have both banks lean it means intake/vaccum leak like I first said. Then you went on to say what hoses to check.
As for that TSB I will look it up tomorrow, I bet when read completey it refers to having one code of the other.
We will wait and see, I bet it is an intake gasket leak, this time of year it gets colder and old gaskets crack over time.
By the way what does the oil dipstick not being put in right have to do with the CEL?
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Originally posted by HITMANinMI:
Originally posted by TronX:
Originally posted by HITMANinMI:
Originally posted by TronX:
What this means is that your Mass Airflow Sensor may have become contaminated. Rather than replacing the MAF as Ford recommends, I have always successfully cleaned MAFs with carb cleaner. If this doesn't work I guess you could always change the fuel filter...
WTH are you talking about, a CEL because of a fuel filter? Also if the MAF was dirty he would get PO171 system to bank 1, ONLY, he wouldnt get PO174 as well.
To the first poster ignore that post by TronX, he has no idea what is talking about.
You think you know everything about cars? The CEL codes do not always tell you what�s really wrong and it can mean many things depending on the maker of the car. The fuel filter its self would not set off a CEL code here, but this was more of a suggestion for fixing related issues. Besides it can help if its never been replaced from years of driving. Along with a few others I can think of like replacing any damaged PCV valves, Inspect each vacuum line for leaks/cracks, clean or replace any air filters, Reseat the oil dipstick and checked the gas cap.. LOL
There is a TSB from Ford.
Article No.: 98-23-10
Date: 11/23/98
Mass Air Flow (MAF) - Sensor Contamination
P0171, P0174 (Fuel system lean, Bank 1 or 2)
There is no procedure for cleaning the MAF; Ford says it has to be replaced.
All though you can clean this part as many here have already done. This same part can also give you many other codes...It's a real Ford Gem.
He should inspect the hose from the PCV valve to the intake.
Sometimes the lower intake leaks at the IMRC seals� (This can cost a lot of money to fix.)
Though it is possible you may only need to clean the EGR ports thoroughly.
The PCM might also be defective ect�?
And if he comes back saying I was right about any of this then I'll be sure to step all over your ego trip.
First off no I admit I dont know alot about cars, most of what I know I learned here and the other part at school.
Secondly when you have both banks lean it means intake/vaccum leak like I first said. Then you went on to say what hoses to check.
As for that TSB I will look it up tomorrow, I bet when read completey it refers to having one code of the other.
We will wait and see, I bet it is an intake gasket leak, this time of year it gets colder and old gaskets crack over time.
By the way what does the oil dipstick not being put in right have to do with the CEL?
There is a long list of P0171/P0174 causes.
- Fuel system
- Excessive fuel pressure
- Leaking/contaminated fuel injectors
- Low fuel pressure or running out of fuel
- Vapor recovery system
- Induction system:
- Air leaks after the MAF
- Vacuum leaks
- PCV system
- Improperly seated engine oil dipstick
- EGR system:
- Leaking gasket
- Stuck EGR valve
- Leaking diaphragm or EVR
- Base engine:
- Oil overfill
- Cam timing
- Cylinder compression
- Exhaust leaks before or near the HO2Ss
There's a plastic ring that seals the oil dipstick, if this is cracked it can cause a Cel code to go off. I know you would think something like this is just crazy, but that�s the kind of BS they are building into cars these days..lol
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Joined: Dec 2001
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Originally posted by HITMANinMI:
Also if the MAF was dirty he would get PO171 system to bank 1, ONLY, he wouldnt get PO174 as well.
will you please read the forums, as I said if both throw a lean code chances are the maf is dirty, very quick fix with electrical contact cleaner
also it could be un metered air that is entering the system after the maf
either way both have been discused here and a search will turn that information up
- 95 Mystique LS - Zetec/5spd
- 99 Contour SeVT Sport - Duratec/5spd
Official NE-CEG Contour/Mustang Family
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Everyone is right to some extent
I had the exact same problem all summer
Drove me "CRAZY"
Changed O'2's- result did not fix, CEL came back on
Cleaned throttle body & EGR port , did not fix
Inspect all vacuum lines, ALL were good
Spray carb cleaner to spot intake leaks etc.
Change dirty air filter
Chandge fuel filter...... same results
Cleaned MAF sensor with non residue cleaner
Improved condition by about 1000 km but light came back on
What I think fixed it.....
Hose connection off the PCV cracked and collapses
when engine on. Makes a 'sucking" sound which most people think is coming off the EGR
Or it could have been as EVERONE speculates, one or some combination of ALL contributing.
Easy and inexpensive to try all of these out.
If I had to start in order
clean MAF, change air filter, check hose off of PCV valve for crack
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