Bad o2 or valves or cat?
#1
01-31-2014 | 04:30 PM
Bad o2 or valves or cat?
Had codes for bad o2 upstream and C#2 misfire...replaced the o2 on the header
got the o2 code to go off but C#2 code is still popping up... so we put new plugs in and switched the Cylinder#2 coil pack with C#4 and reset the obd2 codes and the CEL came on again after 2 start ups...gave the same code for C#2 misfire. P0302 and new code P0420
So called to scheduled with Honda.. I asked how much for a valve clearance (150.00) not bad. but then she said that they would have to do a diagnostic for 120.00... and that the valves are not the problem...as of a few days ago I think the valves have been getting more noisy when it's cold
Then she asked about the fit. told her about the new o2 sensor, OE DENSO 2349060 (234-9060) and new plugs and about the coil pack switch...she says its the o2 that we replaced isn't Hondas and its sending the wrong information to the computer. Could the DENSO be faulty? bought it off rockauto.com
and on top of that the Cat is sending a code to emissions.
got the o2 code to go off but C#2 code is still popping up... so we put new plugs in and switched the Cylinder#2 coil pack with C#4 and reset the obd2 codes and the CEL came on again after 2 start ups...gave the same code for C#2 misfire. P0302 and new code P0420
So called to scheduled with Honda.. I asked how much for a valve clearance (150.00) not bad. but then she said that they would have to do a diagnostic for 120.00... and that the valves are not the problem...as of a few days ago I think the valves have been getting more noisy when it's cold
Then she asked about the fit. told her about the new o2 sensor, OE DENSO 2349060 (234-9060) and new plugs and about the coil pack switch...she says its the o2 that we replaced isn't Hondas and its sending the wrong information to the computer. Could the DENSO be faulty? bought it off rockauto.com
and on top of that the Cat is sending a code to emissions.
#2
02-05-2014 | 02:22 AM
Member
Joined: May 2012
Posts: 150
From: Monkeyville
It's your coil packs. Replace all 4 with quality ones from Honda. Check your plugs, make sure they're clean. If it's oily you might have a leaky valve cover gasket. Remove and replace if that's the case. Easy. It's not the O2 sensor; they're made by vendors which are mostly solid OEMs. It's not valve tappet clearance. Sometimes the noise you hear is just the coil pack grounding somewhere where it's not supposed to making it sound like a noisy valve.
#4
02-06-2014 | 03:22 PM
Member
Joined: Jun 2013
Posts: 629
From: USA
Since you swapped the coils and the misfire didn't move I wouldn't suspect the coils at first. I suspect a liquid is the cause of the misfire.
P0420 is a bad cat. Which means one of two things. You have a misfire that fried the cat. Or a cat that broke apart, pieces were sucked back in and the rings cant seal.
A misfire can be due to many things. If it damaged the cat; its very likely due to a liquid. eg: Valve seals leaking (oil), head gasket leaking (oil or coolant), injectors leaking (fuel)... Liquid in a cat is an instant TKO for the cat. Yes, a plug/ coil not firing would cause an excess of fuel in the cat, but swapping coils and new plugs confirmed its probably not either (make sure to swap the NEW plugs too).
Mileage? What Year is your car?
P0420 is a bad cat. Which means one of two things. You have a misfire that fried the cat. Or a cat that broke apart, pieces were sucked back in and the rings cant seal.
A misfire can be due to many things. If it damaged the cat; its very likely due to a liquid. eg: Valve seals leaking (oil), head gasket leaking (oil or coolant), injectors leaking (fuel)... Liquid in a cat is an instant TKO for the cat. Yes, a plug/ coil not firing would cause an excess of fuel in the cat, but swapping coils and new plugs confirmed its probably not either (make sure to swap the NEW plugs too).
Mileage? What Year is your car?
#5
02-06-2014 | 04:03 PM
215,xxx miles and it's a 2007 sport AT
The first sign was bad mpg like 150 miles if that to a full tank, and the CEL came up about half a day later, got a code for bad up stream o2, replaced it with DENSO OE one and took that code off...but then got the p0420 code also we did drive it 700 miles with the bad o2. IDK if that would mess up the CAT?
and wouldn't the computer run 100% fuel? as a fail safe since the o2 was shot... then when we got home, a new code for misfire in C#2 so we put new plugs in and still same code, so we swap the #2 coilpack with #4 and still C#2 misfire...it runs bad when cold but once warm it runs much smoother.
The first sign was bad mpg like 150 miles if that to a full tank, and the CEL came up about half a day later, got a code for bad up stream o2, replaced it with DENSO OE one and took that code off...but then got the p0420 code also we did drive it 700 miles with the bad o2. IDK if that would mess up the CAT?
and wouldn't the computer run 100% fuel? as a fail safe since the o2 was shot... then when we got home, a new code for misfire in C#2 so we put new plugs in and still same code, so we swap the #2 coilpack with #4 and still C#2 misfire...it runs bad when cold but once warm it runs much smoother.
#6
02-06-2014 | 04:12 PM
Member
Joined: Jun 2013
Posts: 629
From: USA
215,xxx miles and it's a 2007 sport AT
The first sign was bad mpg like 150 miles if that to a full tank, and the CEL came up about half a day later, got a code for bad up stream o2, replaced it with DENSO OE one and took that code off...but then got the p0420 code also we did drive it 700 miles with the bad o2. IDK if that would mess up the CAT?
and wouldn't the computer run 100% fuel? as a fail safe since the o2 was shot... then when we got home, a new code for misfire in C#2 so we put new plugs in and still same code, so we swap the #2 coilpack with #4 and still C#2 misfire...it runs bad when cold but once warm it runs much smoother.
The first sign was bad mpg like 150 miles if that to a full tank, and the CEL came up about half a day later, got a code for bad up stream o2, replaced it with DENSO OE one and took that code off...but then got the p0420 code also we did drive it 700 miles with the bad o2. IDK if that would mess up the CAT?
and wouldn't the computer run 100% fuel? as a fail safe since the o2 was shot... then when we got home, a new code for misfire in C#2 so we put new plugs in and still same code, so we swap the #2 coilpack with #4 and still C#2 misfire...it runs bad when cold but once warm it runs much smoother.
I'm going to guess the #2 plug should be really wet when you pull it out... Smell it. Gas? Coolant? Oil?
#7
02-06-2014 | 04:18 PM
Member
Joined: Jun 2013
Posts: 629
From: USA
I'm not sure what you mean by 100%... in fail safe the car runs off of pre-programmed maps in the ecu at an air fuel ratio of around 11:1~14:1. Just like it does when the car is warming up. It sounds like Honda might not have fully fixed the issue... Let us know if the #2 MisFire comes back.
#8
02-06-2014 | 05:47 PM
so you swapped coilpacks around and the Cyl#2 code still showed up?
Highly suggest you pull your negative battery cable off for several minutes. While waiting, tap the brakes and attempt to beep the horn, and also turn the key in the ignition.
Make sure everything is in the off position and key out, and after those minutes, pop the battery cable back on. Make sure everything is snugged down properly, then start the car and let it idle until the radiator fan kicks on.
This process is called idle relearn procedure. it is CRITICAL to allow the ecu to do it. It is doing its full sweep of sensors and readjusting the fuel and ignition mapping. It may take care of further issues.
Also, tell that bimbo that Denso is the original equipment supplier and tell her to shove her $120 diagnostic fee up her ass
Highly suggest you pull your negative battery cable off for several minutes. While waiting, tap the brakes and attempt to beep the horn, and also turn the key in the ignition.
Make sure everything is in the off position and key out, and after those minutes, pop the battery cable back on. Make sure everything is snugged down properly, then start the car and let it idle until the radiator fan kicks on.
This process is called idle relearn procedure. it is CRITICAL to allow the ecu to do it. It is doing its full sweep of sensors and readjusting the fuel and ignition mapping. It may take care of further issues.
Also, tell that bimbo that Denso is the original equipment supplier and tell her to shove her $120 diagnostic fee up her ass
#9
02-06-2014 | 11:21 PM
Member
Joined: Oct 2013
Posts: 201
From: PA
Interesting diag by honda. I would love to take a look at the tech report.
Driving 700 miles on a bad O2 could have added to the problem. Usually a misfire causes a cat meltdown. The unburned fuel gets pumped through the exhaust and the cat, being a point of slight restriction and chemical reactions, it generates more heat from the added fuel. Its no wonder a cat with 215k miles would meltdown. Even a new cat can melt with a misfire.
I am still unsure of how a cat meltdown creates a misfire on one cylinder only. A cyl 2 misfire should be a code P302. I would expect a code P300 which is "random multiple misfire" since all of the cylinders should be effected, but ecus can do the unexpected sometimes.
I totally agree with the method of swapping the coils and looking for the problem to move. If it doesnt move then we would run a compression test and a leakdown test to check for sealing valves and rings.
With your high miles its a possibility that the engine is weak on that one cylinder. Even the best motors in the world wear out at high mileage.
It also possible you have a bad injector which could also cause a cat meltdown by dumping too much fuel. I would consider checking for injector pulse with a noid light or we have a probe that pics up the pulse on the injector and blinks when you hold the pointer against the injector while the engine is running. The pulse will only tell you if its firing but not if its dumping too much much fuel or none at all.
Im laying odds on a weak cylinder and a tired motor with a bad cat caused by the misfire. The bad O2 was most likely after the cat melted from the extreme heat build up. Sorry for the possible bad news but in my professional opinion it matches that scenario more then a bad cat causing a misfire on just cyl 2. That just doesnt add up.
Driving 700 miles on a bad O2 could have added to the problem. Usually a misfire causes a cat meltdown. The unburned fuel gets pumped through the exhaust and the cat, being a point of slight restriction and chemical reactions, it generates more heat from the added fuel. Its no wonder a cat with 215k miles would meltdown. Even a new cat can melt with a misfire.
I am still unsure of how a cat meltdown creates a misfire on one cylinder only. A cyl 2 misfire should be a code P302. I would expect a code P300 which is "random multiple misfire" since all of the cylinders should be effected, but ecus can do the unexpected sometimes.
I totally agree with the method of swapping the coils and looking for the problem to move. If it doesnt move then we would run a compression test and a leakdown test to check for sealing valves and rings.
With your high miles its a possibility that the engine is weak on that one cylinder. Even the best motors in the world wear out at high mileage.
It also possible you have a bad injector which could also cause a cat meltdown by dumping too much fuel. I would consider checking for injector pulse with a noid light or we have a probe that pics up the pulse on the injector and blinks when you hold the pointer against the injector while the engine is running. The pulse will only tell you if its firing but not if its dumping too much much fuel or none at all.
Im laying odds on a weak cylinder and a tired motor with a bad cat caused by the misfire. The bad O2 was most likely after the cat melted from the extreme heat build up. Sorry for the possible bad news but in my professional opinion it matches that scenario more then a bad cat causing a misfire on just cyl 2. That just doesnt add up.
Last edited by 2010FitSport; 02-07-2014 at 12:04 AM.
#14
02-15-2014 | 01:49 AM
Member
Joined: Oct 2013
Posts: 201
From: PA
Okay....well the report says you have no misfire but you have code P0420 - Catalyst System Efficiency Below Threshold.
So the good news is you dont seem to have a bad engine and the work you did yourself seemed to have cured the misfire but it may have weakened the cat converter since you waited too long to do it.
If the cat is not melted or broken you can drive with that code and nothing will happen. But remember, only if the cat isnt broken inside or melted.
So the good news is you dont seem to have a bad engine and the work you did yourself seemed to have cured the misfire but it may have weakened the cat converter since you waited too long to do it.
If the cat is not melted or broken you can drive with that code and nothing will happen. But remember, only if the cat isnt broken inside or melted.
#17
03-08-2014 | 12:20 AM
Member
Joined: Sep 2012
Posts: 1,226
From: Canada
I got a P0133 - Heated Oxygen Sensor (HO2S) Slow Response Bank 1 Sensor 1 PENDING code. I've since cleared it and it hasn't come back in about 3 days of driving.
I've been getting horrible gas mileage all winter, as you can see in my tag. Some people say its because most of my driving is short trips. True, I drive with a cold engine and by the time it warms up, I'm usually at my destination.
Some people say my O2 sensor is bad, but if it was, wouldn't I get a CEL or a recurring code? I'm thinking maybe I have an exhaust leak? Is worth spending 170$ to replace the O2 sensor? Will it really solve my MPG woes? Also, is the O2 sensor located, right on the cat, like in the picture above or is it closer to the manifold?
I've been getting horrible gas mileage all winter, as you can see in my tag. Some people say its because most of my driving is short trips. True, I drive with a cold engine and by the time it warms up, I'm usually at my destination.
Some people say my O2 sensor is bad, but if it was, wouldn't I get a CEL or a recurring code? I'm thinking maybe I have an exhaust leak? Is worth spending 170$ to replace the O2 sensor? Will it really solve my MPG woes? Also, is the O2 sensor located, right on the cat, like in the picture above or is it closer to the manifold?
#18
03-08-2014 | 01:40 AM
There are two O2's one on the cat and one on the manifold. I got the upstream aka the one on the manifold off rockauto for around 140 bucks...
with your code it could be a failing o2 or what you said a leak...but it depends where the leak is. If its before the O2 sensors it could drop your gas mileage..if its anywhere after the O2 sensors, it prolly wont drop
and I also was getting super bad MPG, and that was a mix of a bad o2 and that led to a bad cat since I drove it 700+ miles like that...and then after that it led to the p0302 code aka misfire in Cylinder 2
with your code it could be a failing o2 or what you said a leak...but it depends where the leak is. If its before the O2 sensors it could drop your gas mileage..if its anywhere after the O2 sensors, it prolly wont drop
and I also was getting super bad MPG, and that was a mix of a bad o2 and that led to a bad cat since I drove it 700+ miles like that...and then after that it led to the p0302 code aka misfire in Cylinder 2
#19
03-08-2014 | 07:31 PM
Member
Joined: Sep 2012
Posts: 1,226
From: Canada
There are two O2's one on the cat and one on the manifold. I got the upstream aka the one on the manifold off rockauto for around 140 bucks...
with your code it could be a failing o2 or what you said a leak...but it depends where the leak is. If its before the O2 sensors it could drop your gas mileage..if its anywhere after the O2 sensors, it prolly wont drop
and I also was getting super bad MPG, and that was a mix of a bad o2 and that led to a bad cat since I drove it 700+ miles like that...and then after that it led to the p0302 code aka misfire in Cylinder 2
with your code it could be a failing o2 or what you said a leak...but it depends where the leak is. If its before the O2 sensors it could drop your gas mileage..if its anywhere after the O2 sensors, it prolly wont drop
and I also was getting super bad MPG, and that was a mix of a bad o2 and that led to a bad cat since I drove it 700+ miles like that...and then after that it led to the p0302 code aka misfire in Cylinder 2
Perhaps that will finally solve the mystery of the 20 MPG I've been getting.
This summer, I'm gonna check the valves and inspect the coils and plugs. Hopefully the new o2 sensor will boost mpg and the previous maintenances will boost it even further.
Thanks so much! +rep
#20
03-08-2014 | 08:03 PM
No prob
and if you need help with the replacement
you will need to take off the heat shield for the manifold its 3 bolts,
then you unplug the harness from the o2 pulling the harness clip to the right hand side...and then also the o2 plug from a clip pulling to the left hand side that holds it in place...the release is on the bottom of the o2 clip
and if you need help with the replacement
you will need to take off the heat shield for the manifold its 3 bolts,
then you unplug the harness from the o2 pulling the harness clip to the right hand side...and then also the o2 plug from a clip pulling to the left hand side that holds it in place...the release is on the bottom of the o2 clip