Codes 171 and 174
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Codes 171 and 174
Hello all...
Have a 99 Explorer 6 cyl OHV. The check engine light came on about 3 months ago with the 171 and 174 codes (too lean bank 1 and 2). I have cleaned the MAF and the EGR valve is about 1 year old. I'll explain why I replaced it in a bit..
I've had a couple of people look at the car and they tell me the same thing that I've read in all of the posts...that it's a vacuum leak. None of them can tell me how to find it. Well, last week I started it and let it run to warm up and when I went back outside I smelled gas. I checked the vehicle and found no leaks and it smells as if it's from the exhaust. Well that would lead me to believe that I'm running to rich and all of the gas isn't being combusted.
The EGR valve was replaced about a year ago after something one of the hose bibs misteriously melted. After I replaced it, it ran fine.
I've checked the PCV valve and all of the vaccuum lines that I can find and it doesn't seem to be there.
I'm more concerned I have a much bigger problem now that I smell gas in the exhaust.
Please help!
Have a 99 Explorer 6 cyl OHV. The check engine light came on about 3 months ago with the 171 and 174 codes (too lean bank 1 and 2). I have cleaned the MAF and the EGR valve is about 1 year old. I'll explain why I replaced it in a bit..
I've had a couple of people look at the car and they tell me the same thing that I've read in all of the posts...that it's a vacuum leak. None of them can tell me how to find it. Well, last week I started it and let it run to warm up and when I went back outside I smelled gas. I checked the vehicle and found no leaks and it smells as if it's from the exhaust. Well that would lead me to believe that I'm running to rich and all of the gas isn't being combusted.
The EGR valve was replaced about a year ago after something one of the hose bibs misteriously melted. After I replaced it, it ran fine.
I've checked the PCV valve and all of the vaccuum lines that I can find and it doesn't seem to be there.
I'm more concerned I have a much bigger problem now that I smell gas in the exhaust.
Please help!
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Joined: Jul 2003
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From: Alvin, Texas.
If you are getting lean codes on BOTH banks, you're not getting enough fuel to make the computer happy.
I would think that suggests a fuel pump being ready to bite the dust (gee, OBD2 isn't so bad for that kind of warning, isn't it?) or even some loose intake manifold bolts.
Unless you have 6 bad injectors (doubtful) or even a bad fuel pressure regulator.
As for the rich smell, maybe the cat is getting ready to die. My Ranger didn't set off a related code, either, but I failed emissions, whether I liked it or not.
I would think that suggests a fuel pump being ready to bite the dust (gee, OBD2 isn't so bad for that kind of warning, isn't it?) or even some loose intake manifold bolts.
Unless you have 6 bad injectors (doubtful) or even a bad fuel pressure regulator.
As for the rich smell, maybe the cat is getting ready to die. My Ranger didn't set off a related code, either, but I failed emissions, whether I liked it or not.
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Ok...so I either have a failing fuel pump or failing cat or both?
Is there anyway to determine for sure what the problem is? Like a way to test the fuel pump?
I'd like to narrow it down before I went spending money on parts I don't need.
Is there anyway to determine for sure what the problem is? Like a way to test the fuel pump?
I'd like to narrow it down before I went spending money on parts I don't need.
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Well, I think I fixed the CEL problem. It was coming up with 171 and 174.
Last night I replaced the two upstream O2 sensors and the problem seems to have gone away (at least no CEL light yet). Feels like I have a little more power than I did as well.
One problem remains however. On cold startup the engine fast idles rough until the engine warms up a bit. After the engine warms up I can slowly rev the engine and at 1500 RPM's I can feel a steady shutter (If I hold the RPM's at 1500.) Below and Above 1500 it feels and runs fine.
Any ideas what would cause this??
Last night I replaced the two upstream O2 sensors and the problem seems to have gone away (at least no CEL light yet). Feels like I have a little more power than I did as well.
One problem remains however. On cold startup the engine fast idles rough until the engine warms up a bit. After the engine warms up I can slowly rev the engine and at 1500 RPM's I can feel a steady shutter (If I hold the RPM's at 1500.) Below and Above 1500 it feels and runs fine.
Any ideas what would cause this??
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I highly doubt that you fixed the problem. Otherwise you would have 02 sensor codes. Here at the dealership we do 1 set of upper and lower intake gaskets weekly. and that will give you a bank 1 bank 2 lean condition. Also monitor fuel pressure. That is where computer diagnostics is cheaper than just replacing. You could monitor all O2's and watch them switch, if they are switching then they are working fine. Also too those codes dont seem to be much of a problem when it warms up, its usually after a few good warm days and then a really cold one. Go to the garage and tell them you want all upper and lower intake o-rings and gaskets, they are very cheap, and will fix you right up. Thats why you are still feeling what you are. Its still sucking air.
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p 171 and 174
Pat
I just fixed my truck and I had them same to codes, How I found my leak was I took carb cleaner and with your truck Running You take the carb cleaner and spary it around the intake gasket and plenium gasket If your truck idles higher then what it is at Idle then you have an intake gasket leak, You might want to check around the Egr tub it self where it goes up into the plenium, there is a ruber gasket in there that can get bet out of shape and will cose your intake to suck to much air in there. that was the problem with my truck, and it runs like its brand new and it was about a half hour fix. Good luck let me know if you found your leak..
I just fixed my truck and I had them same to codes, How I found my leak was I took carb cleaner and with your truck Running You take the carb cleaner and spary it around the intake gasket and plenium gasket If your truck idles higher then what it is at Idle then you have an intake gasket leak, You might want to check around the Egr tub it self where it goes up into the plenium, there is a ruber gasket in there that can get bet out of shape and will cose your intake to suck to much air in there. that was the problem with my truck, and it runs like its brand new and it was about a half hour fix. Good luck let me know if you found your leak..
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