Code 172 and my exhaust
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Senior User
Joined: Mar 2003
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From: Kickapoo, IL.
Code 172 and my exhaust
Been having a little trouble and the light finally came on the other day. Went to auto zone for a read and the only code was 172. I understand that this states pretty much that the o2 sensor isn't staying hot enough and I think it is because of my exhaust or no exhaust. I have a 95 f150 with the 302 and the exhaust is pretty much straight. One cat have been removed and the other is empty. I still have the two manifolds coming into the first cat and that single tube proceeds the length of the truck where it splits for duals out the back. I am thinking that since the exhaust is free flowing that this is causing my low temp on the sensor. Or is it just a bad sensor?? If I add an actual muffler will that add enough back pressure that it would provide the needed heat to the sensor?
thanks
Matt
thanks
Matt
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Code 172 is system lean...if I'm looking at the right reference. The exhaust system downstream of the O2 sensor is irrelavent to this, and the efi system has more than enough range to adjust to whatever air flow rate the motor can generate. Your problem is upstream of the O2 sensor in the form of a leaky exhaust or a partially missing and/or not properly plugged air pump system.
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Senior User
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From: Kickapoo, IL.
when you are talking "air pump system", do you mean the smog system. Where would I look for the "partially missing and/or not properly plugged air pump system". Is that the stuff that comes off the manifold.
I was wanting to rip all that smog stuff out anyway. I hear people doing that all the time. Is it just pluggin the holes or tubes and be done with it. Or is there more to than that.
I was wanting to rip all that smog stuff out anyway. I hear people doing that all the time. Is it just pluggin the holes or tubes and be done with it. Or is there more to than that.
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Yes.. the "air pump system" is part of the smog equipment. There is an air pump on the lower passenger side of the motor, and a bunch of plumbing and valves that either direct air into the heads at the back, down to the cats or to atmosphere. What condition is yours in? Is it all intack connected and functioning?
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From: Kickapoo, IL.
I know that I don't have anything going to my remaining cat. Besides that I will have to look and get back to you.
If I rip all that out, just for the added cleanliness, will I just have to make sure everything is plugged?
If I rip all that out, just for the added cleanliness, will I just have to make sure everything is plugged?
FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Originally Posted by mstaser
If I rip all that out, just for the added cleanliness, will I just have to make sure everything is plugged?
As indicated a leak in this system is the same as a leak from a cracked manifold.. it could cause your problem. You could also have dirty injectors or a bad sensor though.
Fleet Mechanic
Joined: Sep 2003
Posts: 1,279
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From: savannah,ga
you can also have a vacuum leak that will cause a lean condition
i checked a truck today that had a new egr valve and the installer
let the gasket slip down
severe vacuum leak and a bunch of codes
i checked a truck today that had a new egr valve and the installer
let the gasket slip down
severe vacuum leak and a bunch of codes
