Chasing the p0108 code

[Mbrooks420]

All it technically means is that it’s leaking. You’ll have to pull it to see why.

 

[07 Eddie Bauer]

All it technically means is that it’s leaking. You’ll have to pull it to see why.

So I just went out and pulled the upstream O2 sensor...took it for a drive. It was loud but it has more power than it's ever had

 

[Ruddy]

Update... The air leak I heard is actually coming from the o2 sensor in the cat. Does this mean the cat is clogged? Or if it's a rust hole would it make my truck run like crap?

if you have an air leak near that sensor it will read incorrectly from all the outside oxygen being sucked in

 

[Stynx]

Were you able to snug it back down and stop the leak? Did you try cleaning the sensor with electronics cleaner?

 

[07 Eddie Bauer]

Were you able to snug it back down and stop the leak? Did you try cleaning the sensor with electronics cleaner?

I ended up removing the upstream O2 sensor. The truck has full power with it out. I'm thinking the cat is clogged?

 

[Fix4Dirt]

I ended up removing the upstream O2 sensor. The truck has full power with it out. I'm thinking the cat is clogged?

could be the cat, but have you verified its not the o2s and the exhaust leak checks out?

 

[Stynx]

I ended up removing the upstream O2 sensor. The truck has full power with it out. I'm thinking the cat is clogged?

Maybe but cats aint cheap. I take that there was not a rust hole? Just wondering what would happen if you cleaned the o2 sensor and replaced it. Does it still sound like it's leaking when the sensor is replaced?

 

[07EddyB]

If it was loud then that means that you removed it completely and ran it leaving a hole before the cat. I wouldn't think that size hole would improve things that much with a clogged cat but it appears that it did. If it was the sensor - then logic would say if it's flopping in the wind now and it's running better then it's getting more clean air than it ever did before so how would a leak around it supplying fresh air to it screw things up more than it being physically out of the exhaust stream?
Sounds like the air leak was air coming out - not being sucked in.

 

[07 Eddie Bauer]

could be the cat, but have you verified its not the o2s and the exhaust leak checks out?

The leak is like a hiss. Like it's coming out a small hole. I'm buying new o2 sensors tomorrow. I'm gonna try them before I make my move on the cats. I did try unplugging them first but it didn't change anything until I took it out

 

[07 Eddie Bauer]

If it was loud then that means that you removed it completely and ran it leaving a hole before the cat. I wouldn't think that size hole would improve things that much with a clogged cat but it appears that it did. If it was the sensor - then logic would say if it's flopping in the wind now and it's running better then it's getting more clean air than it ever did before so how would a leak around it supplying fresh air to it screw things up more than it being physically out of the exhaust stream?
Sounds like the air leak was air coming out - not being sucked in.

Yes it's coming out. Hissing like a small hole. I took the o2 sensor out because I seen it on another post...said it was a good way to test the cats so when I did it I was shocked. Besides the loudness it was like a brand new truck. I'm almost certain now that it's the cat

 

[07EddyB]

Yes it's coming out. Hissing like a small hole. I took the o2 sensor out because I seen it on another post...said it was a good way to test the cats so when I did it I was shocked. Besides the loudness it was like a brand new truck. I'm almost certain now that it's the cat

It ran better without the sensor in the hole. Find another way to plug the sensor hole and if it still runs bad then it's the cat.

 

[94Eddie]

Here is how to test for a clogged catalytic convertor.

 

[RedDog1]

This is a pretty good discussion on that code.
P0108 Manifold Absolute Pressure/Barometric Pressure Circuit High Input
Good luck!

 

[roe]

I'm wonder how I should approach this. I've done the plugs and wires, fuel filter, tried to find a vacuum leak with no success. Is it a bad cat? MAP- EGR valve? O2 sensor? I've got a loss of power, feels like something holding it back and it has a rough idle but not all the time. This morning when it was cold it didn't want to go at all chugged real bad took me about a mile to get up to 60. Motor has around 95 k the truck has 250k. Any help would be greatly appreciated thx

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Timing chain guides?

 

[drbenz]

The video is quite good if you happen to have access to a scanner. For those of us that just want a quick (and pretty accurate) idea on the cheap try this: hook up a vacuum gauge to manifold vacuum and see what the idle vac reading is. Then rev the engine up to around 2K to 2500. The vacuum reading will fall at first and then recover as the engine speeds up. If the exhaust is ok the higher rpm vacuum reading will be at least as high as the idle reading if not higher (yours likely won't be). A hiss in the exhaust combined with the engine running much better with the o2 sensor removed would mean to me that the exhaust is stopped up and is trying to get out anywhere it can (noise) and if it is able to get out (O2 sensor out) things start to work better.
If that still isn't enough then you can make a pressure fitting that will let you plug into the exhaust itself in front of the cat and let you read the actual exhaust pressure. I used an old 02 sensor but some drill a hole in the exhaust pipe and then plug the hole when they are done with the test.

 

[Beachcomber86]

Have you traced out the harnesses? Some models have an issue with brittle wiring insulation that have caused a host of problems.

If it’s not a wiring issue, I’d suspect you’re getting too much fuel. If you clear the codes does the cylinder 1 misfire come right back?

Check this thread: Found my ghosts in the machine

 

[Beachcomber86]

Have you traced out the harnesses? Some models have an issue with brittle wiring insulation that have caused a host of problems.

If it’s not a wiring issue, I’d suspect you’re getting too much fuel. If you clear the codes does the cylinder 1 misfire come right back?

Check this thread: Found my ghosts in the machine

 

[Farmgirl22]

I'm wonder how I should approach this. I've done the plugs and wires, fuel filter, tried to find a vacuum leak with no success. Is it a bad cat? MAP- EGR valve? O2 sensor? I've got a loss of power, feels like something holding it back and it has a rough idle but not all the time. This morning when it was cold it didn't want to go at all chugged real bad took me about a mile to get up to 60. Motor has around 95 k the truck has 250k. Any help would be greatly appreciated thx

View attachment 428581 View attachment 428582

Hey our Vin numbers are one digit apart, I have the exact same car, with exact same problems. I had to change my heater hose vac due to the fact that it lost all the fluids because the little plastic pos broke. Still having surge issues, rough idle. I'm gonna try a wiring harness next. Change out all the hoses. Get a new mass air flow sensor and connector. Then probably check out the oem. I am not a mechanic but, I'm following this guy chrisfix on YouTube and step-by-step going through each thing until I get to the bottom of it. He's good! Check EGR valve. Bad alternator could be the culprit , too. At 200+ miles, these things just go.

 

[drbenz]

Since you have mentioned it, a bad alternator (actually defective diodes) can cause all sorts of odd problems. The reason is that a leaking diode will allow ac voltage on what should be a rectified dc line and computers see what they think is a "signal" from a sensor and there is no telling what computer will do with it. Several years ago my Explorer started throwing a code saying that the distributor sensor was bad and it turned out to be just a diode problem. When I took the alternator to the shop to get it fixed they said they saw a lot of "transmission problems" that were really caused by stray ac from the alternator diodes.

 

[Islandguyhere]

Thx for the help everyone. I'll post my results as soon as I fix it

Check o ring on map. Likely that it. Reset cel after replacing o ring. Drive 50 miles even if cell comes on. Ring has to expand/seat. Reset cel. Likely problem solved.

P0108 classic throw parts at it for easy fix. GL.