[oldred]

I just ran a scan on a neighbors car because the "check engine" light came on, a 1996 Ford 4.6, and got the following code-P0430 "Catalyst Efficiency Below Threshold" (Bank 2). Could someone decipher this for me and tell me what I am looking at here?

Thanks and please pardon my ignorance of what this code means.

[OneMoreTime]

I would suspect the catalytic converter or an O2 sensor..From that description..Likely a cat on a car of that year..But then if you have a way to see if the O2 sensor is working just fine I woudl check that out before buying a Cat..

Sam

[matt167]

if you have a non contact pyromater, get the engine up to temp and into closed loop.. then check the temp in front of the cat, then behind the cat. it should be approx 5* hotter behind the cat due to chemical changes. if it is the same or colder, the cat is bad.

[T-bucket23]

Remove and clean the MAF. Very carefully with a swab and carb cleaner. This is a real common issue on those. This is assuming the O2 sensors are working.

[oldred]

T, Since the only code it shows is the Catalyst out of range would it be safe to assume the O2 sensor is OK?

[T-bucket23]

Sorry, I gave you bad info, I was thinking of the bank lean codes. Thats what I get for typeing while watching the Celtics.
The cat code you are seeing is either a bad O2 sensor or an exhaust leak ahead of the cat or a bad cat. The computer compares the O2 that is ahead of the cat with the one after it. The one before it should be swinging between .1 and .9 volts. This is hard to see with a digital meter, and analog meter or a scope is your best bet. The one after the cat should usually be almost flat. In order to properly diagnose it you really need a 2 channel scope or a good graphing scanner. If the O2 sensors check ok and the exhaust checks it is most likely a bad cat.
Do yourself a favor, if you need any of these parts, get them from a dealer. The aftermarket O2 sensors are poor replacements usually. We have seen many that are way out of spec. Same with the cat, those 79 dollar replacement cats are junk. We have seen more people waste money putting on replacement parts that are no good. Another thing to look at is the connectors and wireing on the O2 sensors, we have seen several cut or damaged. This is why if we connect the scanner and see unusaul readings we usually will probe the sensor as well to make sure it is not just a connection issue.

[T-bucket23]

How many miles on this car.
If it is over 100K you most likely need O2 sensors. The tough part is that may have 4 and it gets expensive to guess. Good luck with it.
Just a side note, it is usually easier to get the O2 sensors out if the pipe is hot.

Chet

[oldred]

I went AutoZone (I know ) and had them print out a diagnoses for this code and it lists three probable causes for the catalyst failure, Engine misfire on one or more cylinders, large vacuum leak or excessive oil consumption. There was apparently no vacuum leak and the engine does not use any oil so I pulled the plugs and they were bad, awful would be a more apt description. All of them were dry and the proper tan color but the electrodes on a few of them was all but burned away and these showed traces of carbon from unburned fuel. The car has 118000+ miles and from the looks of these plugs they probably are the originals so I changed them and the plug wires, Autolite Platinum and Bosch wires. One thing I forgot to mention is that this thing idles too fast in addition to the "check engine" light but after changing the plugs/wires and erasing the code the light did not come back on but it is still idling too fast. Other than the slightly high idle it seems OK now but I told him he could probably expect the light to come back on and the code would most likely return after driving it a while because the cat is probably bad. Since the plugs were in that shape I strongly suspect the O2 sensors are original also so do you think they should be the next step or should we just plan on replacing the cat at the same time?

[matt167]

Originally Posted by oldred

I went AutoZone (I know ) and had them print out a diagnoses for this code and it lists three probable causes for the catalyst failure, Engine misfire on one or more cylinders, large vacuum leak or excessive oil consumption. There was apparently no vacuum leak and the engine does not use any oil so I pulled the plugs and they were bad, awful would be a more apt description. All of them were dry and the proper tan color but the electrodes on a few of them was all but burned away and these showed traces of carbon from unburned fuel. The car has 118000+ miles and from the looks of these plugs they probably are the originals so I changed them and the plug wires, Autolite Platinum and Bosch wires. One thing I forgot to mention is that this thing idles too fast in addition to the "check engine" light but after changing the plugs/wires and erasing the code the light did not come back on but it is still idling too fast. Other than the slightly high idle it seems OK now but I told him he could probably expect the light to come back on and the code would most likely return after driving it a while because the cat is probably bad. Since the plugs were in that shape I strongly suspect the O2 sensors are original also so do you think they should be the next step or should we just plan on replacing the cat at the same time?

just verify the cats condition the way I pointed out ( HF has the pyromaters, for around $50 you can buy 1 of the better models, I have 1 and there fine, once you put good batteries in them ).. if it's good then move to the 02 sensors.. Cats can be expensive also

[oldred]

Matt- I will do just that, I have been wanting to get one of those pyrometers anyway but I was a bit skeptical of the one from HF and could not justify the cost of a good one for the few times I would need it. Don't know why I was avoiding the one from HF anyway I have a bunch of the HF stuff and most of it works just fine.

[carsavvycook]

For the idling too high problem, if you don find any source of a vacuum leak, pull the EGR valve and look to see if it has any carbon holding it open. Also if you hear any rattling in the exhaust that cat is coming apart and is bad. I have seen this a number of times from vehicles that are not well maintained.

[matt167]

Originally Posted by oldred

Matt- I will do just that, I have been wanting to get one of those pyrometers anyway but I was a bit skeptical of the one from HF and could not justify the cost of a good one for the few times I would need it. Don't know why I was avoiding the one from HF anyway I have a bunch of the HF stuff and most of it works just fine.

just change the battery with 1 a good brand. otherwise they work good for a few minuites, then go 10* off ( lower ). I used to check it with the digital thermomater I have in the house and do the math, but I just got the battery and it works fine