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#1
telim

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Hey guys,

I need some help with a Check Engine Light that keeps coming on. Roughly two months ago, back in May, my engine light came on so I pulled the code (P1131) HO2S Bank 1 Sensor 1 (A/F ratio too lean). I figured that 02 sensor must be malfunctioning so I went to my nearest Advance Auto Parts shop and picked up a Bosch 02 sensor for Bank 1 Sensor 1 (I also read from a post here that Bank 1 Sensor 1 is the one closest to driver in the exhaust manifold i.e. not the one near the front the car next to the radiator, I hope this is correct.) . I replaced the 02 sensor, cleared the code, and I was light-free until two months until yesterday. I heard sometimes these code could also mean a problem with the MAF sensor so I cleaned that with CRC Mass Air Flow cleaner then I cleared the code and within a day the Check Engine Light came back on. I'm not sure if the problem is really the 02 sensor or something else. Anyone have any ideas? Thanks.

#2
djdevon3

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Have you checked for vacuum leaks? Do an intake manifold leak test.

#3
telim

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Have you checked for vacuum leaks? Do an intake manifold leak test.


Thanks for the sugestion! I'm gonna give that a shot. I have to admit though, I've never done this before. This involves spraying carb cleaner near the intake manifold and listen for an idle change, correct? Do I have to worry about carb cleaner being flammable near a hot engine?

#4
PrinceValorum

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I'd do it from a cold startup so you don't have to worry about it as much. A fire extinguisher on hand would never hurt. Obviously don't aim for the exhaust manifolds, either!

#5
djdevon3

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There is danger involved so go slow and only spray a tiny bit at a time. Do not under any circumstances get the aerosol can next to active electrical lines of any voltage. The can could explode. That and a fire in the engine bay from heat are why doing it on a cold-started engine is advised. There are many people every year who are severely injured from incorrectly doing a leak test with carb cleaner. It can be a quick and inexpensive way to test for intake leaks but also very dangerous. Use with extreme caution or take it to a mechanic so they assume the liability and testing.

If you are unfamiliar with mechanical troubleshooting and feel uncomfortable working around fuel and electrical lines please please take it to a mechanic.

#6
telim

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WIll do! I'll give this a shot first thing in the morning.

#7
telim

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I forgot to ask: Where is the most common places around the intake manifold do leaks usually occur or is there not really a common spot?

#8
djdevon3

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To my knowledge there isn't a most common location. Due to vibration and intake air I would guess on the 4 cylinder the best place to check would be closest to the throttle body. I have seen plenty of videos that show leaks in just the opposite location so it's really up in the air. Gotta test around the whole thing including the bottom but that's damn tough to get near without touching an electrical line.

See what can happen when a metal aerosol can touches a live 12v line? Fireball of something burns very hot and rapidly. Only a Class B fire extinguisher can put it out though you probably wouldn't be able to get to one in time before it burns off into vapor.

#9
telim

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To my knowledge there isn't a most common location. Due to vibration and intake air I would guess on the 4 cylinder the best place to check would be closest to the throttle body. I have seen plenty of videos that show leaks in just the opposite location so it's really up in the air. Gotta test around the whole thing including the bottom but that's damn tough to get near without touching an electrical line.

See what can happen when a metal aerosol can touches a live 12v line? Fireball of something burns very hot and rapidly. Only a Class B fire extinguisher can put it out though you probably wouldn't be able to get to one in time before it burns off into vapor.


Noted. I heard that I can test with a propane torch, just fit a rubber hose at the end and hunt for the leak. They say it supposedly a lot safer. Does it really work?

#10
djdevon3

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You would use the propane gas not the lit torch. It's the same concept and comes with the same dangers. You might be able to minimize the risk by wrapping the aerosol can in a non-conductive material like a thick towel or rubber coating. Just don't drop it. You are almost literally playing with fire. Be careful, be safe, be cautious.

#11
telim

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You would use the propane gas not the lit torch. It's the same concept and comes with the same dangers. You might be able to minimize the risk by wrapping the aerosol can in a non-conductive material like a thick towel or rubber coating. Just don't drop it. You are almost literally playing with fire. Be careful, be safe, be cautious.


Thanks for the advice!

#12
telim

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Alright, so I checked fairly throughly if there were any vacuum leaks around the intake manifold and around the air intake and everything looked very good. No vacuum leaks I can find. Anyone have another other possible idea?

#13
MazdaMikeV6

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My car has a similar situation. Ever figure out what it was?

#14
Tiberianx

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Before determining there's a vacuum leak in the first place, you should hook up a vacuum gauge (cost about $20) to one of the intake manifold port holes, the hole where the pcv hose is hooked up to would probably be a good spot if I'm not wrong. Normal vacuum reading on a idle engine should be a steady still needle between 15Hg-22Hg on the gauge. If it is fluctuating rapidly between 15Hg-22Hg, then you have a vacuum leak somewhere in the intake or even the valve cover gaskets. If gauge reads normal then your okay. So hook the vacuum gauge up, start the engine up, and see whats up.

Although looking for vacuum leak on a V6 is a little difficult especially when you're trying to reach back there with that large bottle of can sprayer. However, the best way to look for a vacuum leak on any car is go to a shop that carry's a smoke machine and have them smoke test it with the engine off. Where ever the smoke comes out of, that's where your vacuum leak is coming, there's a possibility that there is more than one leak, so check thoroughly. I don't know how much shop will charge for using it but not many mechanics can afford a smoke machine that cost over $1,300 so good luck.

#15
Tiberianx

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What the :wacko: , didn't know this topic was posted last year. Ah phooey




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