Clogged Pre-cats
#1
Clogged Pre-cats
What are the signs that a pre-cat is failing/clogged?
There are a lot of different answers I hear, just wanted to get it out there.
from another forum:
CELs for O2 sensors reading below standard levels
presistant ticking sounds
oil consumption
loss of power
in-ability to rev
There are a lot of different answers I hear, just wanted to get it out there.
from another forum:
CELs for O2 sensors reading below standard levels
presistant ticking sounds
oil consumption
loss of power
in-ability to rev
#2
Ultimate test is to floor it going on highway, however you could also blow your engine doing this from the exhaust backpressure.
This is the perfect spot for these links:
All Catalytic Converters - How do I know if my catalytic converter is defective?
How to check your vehicle's catalytic converter. - YouTube go 30 secs in to see how to test for backpressure
Reasons For A Converter Failure
The only way to know is by visual inspection and/or backpressure test as in the You Tube video above.
This is the perfect spot for these links:
All Catalytic Converters - How do I know if my catalytic converter is defective?
How to check your vehicle's catalytic converter. - YouTube go 30 secs in to see how to test for backpressure
Reasons For A Converter Failure
The only way to know is by visual inspection and/or backpressure test as in the You Tube video above.
Last edited by UseYourNoggin; 01-30-2012 at 08:44 AM.
#3
what happens when you floor it on the highway? (I'm not going to do this though, just wondering if there is a performance issue)
The exhaust guy said it was hard to get into testing it? He was going to do something with the O2 sensors but said one of them was hard to get to on the 6. Is it easy to do a backpressure test as noted in the video on the 6? The pre-cats seemed kind of out of the way?
The exhaust guy said it was hard to get into testing it? He was going to do something with the O2 sensors but said one of them was hard to get to on the 6. Is it easy to do a backpressure test as noted in the video on the 6? The pre-cats seemed kind of out of the way?
#4
what happens when you floor it on the highway? (I'm not going to do this though, just wondering if there is a performance issue)
The exhaust guy said it was hard to get into testing it? He was going to do something with the O2 sensors but said one of them was hard to get to on the 6. Is it easy to do a backpressure test as noted in the video on the 6? The pre-cats seemed kind of out of the way?
The exhaust guy said it was hard to get into testing it? He was going to do something with the O2 sensors but said one of them was hard to get to on the 6. Is it easy to do a backpressure test as noted in the video on the 6? The pre-cats seemed kind of out of the way?
Your 0-60 time will no longer be around 7-8 seconds. It will bog down and increase your 0-60 time depending on how bad it is. Same thing on highway it will bog down, backpressure will build up and break something on the engine in extreme cases.
Performance: Pre-cats do nothing for performance, they just negate it. The more plugged, the less performance, and the more chance your engine will go Boom Boom (not Zoom Zoom)
I just looked @ mine. Not much room, removing O2 sensor is the best route (heat shields just before it with not much room @ manifold). The front one is easier to get at than the back one. Which one was exhaust leak from. If it's front one easy, rear = dilemma.
After the pre-cat should not be an issue.
Pic on right is a good Pre-Cat, view thru O2 sensor.
Last edited by UseYourNoggin; 02-17-2012 at 03:10 PM. Reason: Performance? Really? Pic#2
#6
The point is the side with the leak that got fixed is the problem side, at least get that one checked properly and change the O2 sensor. If it's the front get it checked. There is no excuse from any mechanic not to get the front one checked out properly!! The pic in previous post is from Front one.
Could the loose bolt have come loose from worn motor mounts: possibly. Excess engine twisting stresses the exhaust into stretching & twisting: this is why you should look closer at flex exhaust tubing for leaks. Maybe the exhaust leaks at this point. Get exhaust checked out with car in gear and push down on accelerator to make exhaust twist and check it out at that point.
#7
I believe it was the rear, if that is by the firewall. I had them check again for any leaks at an exhaust shop, they said there wasn't any leaks in the exhaust system
I am trying to get the cats/pre-cats properly checked for backpressure but everyone I seem to go to doesn't want to check them. Some say they're too hard to check out or they don't have the capacity to do so, others just say they're fine.
I am trying to get the cats/pre-cats properly checked for backpressure but everyone I seem to go to doesn't want to check them. Some say they're too hard to check out or they don't have the capacity to do so, others just say they're fine.
#8
I believe it was the rear, if that is by the firewall. I had them check again for any leaks at an exhaust shop, they said there wasn't any leaks in the exhaust system
I am trying to get the cats/pre-cats properly checked for backpressure but everyone I seem to go to doesn't want to check them. Some say they're too hard to check out or they don't have the capacity to do so, others just say they're fine.
I am trying to get the cats/pre-cats properly checked for backpressure but everyone I seem to go to doesn't want to check them. Some say they're too hard to check out or they don't have the capacity to do so, others just say they're fine.
I have changed all my O2 sensors (en-route on trying to fix lean code) without too much difficulty (however my vehicle has less than 1/2 mileage of yours). Time for a new shop, again?
They should be able to check backpressure in O2 sensor hole before pre-cat (front or rear pre-cat). Drill new hole after pre-cat (it may be hard to remove O2 sensors unless you intend to replace them). (As per video back pressure should be done before and after the pre-cat).
Change the first O2 senor that checks air/fuel ratio at least on the rear firewall side where the leak was.
You have enough mileage to get O2 sensors before pre-cat changed: Replace Oxygen Sensor - O2 Sensor Circuit Replacement - Popular Mechanics
GOOD LUCK. Decisions, decisions.
Last edited by UseYourNoggin; 02-08-2012 at 12:25 PM.
#9
Just read this from someone else on another forum:
Took my car into the shop today. They did a back pressure test and it seemed okay. After they took a look inside the pre cat they said that it was pretty much done for. This is after getting a P0431 code. They are going to check out the other ones as well.
My car is an 04 and has 64k miles.
Goes back to my Post #2.
Something else I would like to point out: Driving around normally and accelerating too much on slippery surfaces will cause the Traction Control Sensor to kick in which turns off spark but sends raw fuel to the pre-cats. This is not good for pre-cats. Normally I drive with TCS OFF (except in snow or ice-----then accelerate very gently).
CLEAN YOUR CATALYTIC:
Took my car into the shop today. They did a back pressure test and it seemed okay. After they took a look inside the pre cat they said that it was pretty much done for. This is after getting a P0431 code. They are going to check out the other ones as well.
My car is an 04 and has 64k miles.
Goes back to my Post #2.
Something else I would like to point out: Driving around normally and accelerating too much on slippery surfaces will cause the Traction Control Sensor to kick in which turns off spark but sends raw fuel to the pre-cats. This is not good for pre-cats. Normally I drive with TCS OFF (except in snow or ice-----then accelerate very gently).
CLEAN YOUR CATALYTIC:
Last edited by UseYourNoggin; 01-16-2013 at 06:34 PM. Reason: TCS
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