M00n3at3r

So I just got a new engine in my car and a couple days after driving it, I noticed the exhaust note changed and a couple days later I got the dreaded P0420. I'm stumped and I'm really not sure what could have caused it. On top of that, my plugs and exhaust pipes have this strange tan dust on them. I asked my mechanic about the dust and he told me it was because I was driving like a normal person. Maybe he is right and I'm just used to a rough running engine, but even in my wife's car that runs like brand new, there aren't deposits like that. Also, I had my cat replaced about 3 years ago, could it really have gone that quickly? I've included pictures of my exhaust. There are two manifolds, one, without the metal plate is the original one, and the second is the one that came with the engine that I ran for a little while after getting the car back.

ezone

That's what killed the cat.

You can ruin a brand new cat in a matter of only minutes if the engine runs bad enough.

Got pics of the inside of the cat? Is the element inside it all broken apart?

M00n3at3r

Unfortunately not. I haven't tried to tackle disconnecting the central silencer from the cat. By rough though I just mean either a blown HG or warped head. Never burned any coolant, or if I did it was minimal, and the oil needed to be topped off at 3k and then changed at 4k but other then that it was good. I was under the impression the head was warped though and with it burning oil at the rate it was, although not awful, I was taking preventative measures...that have now become a pain in my side. Never paying someone to do a engine swap again.

ezone

I figured when you said it was rough running that it had been running with misfiring going on.

Oil burning can slowly ruin a cat,
Coolant can slowly or quickly poison a cat
The contaminants can coat and clog the pores of the element so it cannot store and release oxygen properly.

Misfire and rich running can kill a cat in a hurry.
Lean and running out of fuel can kill a cat too, but it's not very common.

M00n3at3r

It seems like I hit a wall. Like after 4k it's sluggish. It just gets really loud and slowly climbs. I could almost red line my other one without much effort. I normally shift right around 4K, so I don't make a habit of running it past that, plus I'm concerned I'll blow a seal. I have a laundry list of things to test before conclusively say the cat is bad, but I'm stumped on the whole tan dust thing. My brother, a mechanic, said he though it was either somehow related to the cat, or I was burning coolant. I haven't found anything to back either of those thoughts though.

ezone

Restriction. Intake or exhaust. Likely exhaust.

Disconnect the exhaust from the header or first pipe (disconnect ahead of the cat) and drive it.

If it will pull all the way to redline with cat disconnected then cat is clogged--- or broken apart and chunks are clogging the exhaust somewhere.

Bang on the exhaust pipes with a rubber mallet, listen for internal rattles (cat chunks)


What did you expect to see?

M00n3at3r

Honestly I'm not sure, I guess just clean, the plugs are brand new so I expected them to still look it. I've been inside a few engines and never seen anything like that, so I was a little concerned that something was wrong. As for the cat, I'll check my like and do a bang test, then drop the downpipe and see what happens.

ezone

Spark plugs always show the last conditions they were exposed to.....If the last action was a cold start then shut off, the plugs would probably be dark and kinda sooty.


Manifold and pipes will be ashy under most normal running, with some soot depending on last run. Carbon is easily burned out close to the engine where the exhaust stays hottest, but pipes can stay blacker as you get further away from the engine.

M00n3at3r

Well, after creeping out of my neighborhood at 9pm in fifth gear so not to wake up the neighbors, I got the car onto a back road, cringed and opened her up. Seems like it went up much smoother and the exhaust note seemed stable instead of jumping to loud and a wall on the acceleration. So, next I'll move to checking for blockage. I've removed the muffler and that didn't make a change, I'm going to wait until I get replacement nuts for the cat to silencer. But, I would assume it's pretty conclusive...cats bad.

ezone

I've been running open pipes on my bikes for years. Neighbors hate me.



If your engine pulls good all the way to redline at wide open throttle now, that's pretty conclusive.

M00n3at3r

Well I didn't red line it, out of fear of a friendly neighborhood officer coming after me, but past 4k it steadily moved up so yes, I would agree that's where my problem is. So the next problem...how long can I run with a bad cat and is there a recommendation besides oem that will be adequate...or just skin me and say don't skimp...i know.

ezone

Much of the time with a restricted exhaust you can baby it and get the RPM much higer than it can go when you floor it....so consider that info in your evaluation.

M00n3at3r

So take it back out and dump it with the downpipe dropped?

ezone

I would have given it hell on the first drive.

I'd stand on it wide open all the way through first gear and let it make its shift at redline if it's an automatic trans.
I'd back off the gas for the shift or as soon as I know it's improved, I don't want the trans making the shift under full throttle on a older car with a bunch of miles on it. (I don't want the patient to die on my operating table)

5 seconds of godawful noise, then inconspicuously burble on back to the homestead.
You may want to wait until daylight though.

M00n3at3r

Well I did so and had to sneak past an officer. It ran up fine, manual by the way, lots of unhappy back fires. I reconnected everything and took it out for the same drive the same way and it seemed to hit red line fine, just a little slower, and slower then my old engine still. Maybe I'm just being ****? There is still that overwhelming noise. Didn't have that with the old engine. Maybe if I switch all the sensors, maybe injectors also, over from the old engine and see if that changes anything?

PMI

Tan color is normal for a plug after a while, rust/orange color, nor so much.. Rust-color dust may be a result of someone, perhaps b/f you owned the engine, using an additive like an octane booster.

"Spark Plugs Turned Orange"

If an exhaust suddenly becomes much more noisy, there is def. something amiss with the cat or exhaust.

Aftermarket cat converters are often much lower quality than oem replacements. I assume the engine was replaced for a reason, so if the cat converter was damaged when orig. engine went bad, it may have just died on you a few days later, from damage done earlier.

You could get a "test" pipe (less than $70 on ebay, craigslist etc) to run the car w/o a cat converter, but with exhaust intact. Or, just call a local salvage yard and try to get a used oem cat converter, if you are comfortable with using old parts. A cheap universal cat ($50 new online) welded by a local muffler shop should be around $150 installed for a small 4-cyl engine. A really nice Magnaflow high-flow cat about $100 more.

M00n3at3r

Well I just so happened to add some octane booster on the same tank of gas I checked the plugs. If you read down the thread I mentioned I replaced the engine because I thought the head had warped and it was burning a quart of oil every 3k miles which I didn't like so I replaced it as a preventative measure so I didn't run into worse problems down the road, now it's becoming a pain because I thought I was being smart.

As for the exhaust I don't think there is any relation, but after I got the car back I replaced all 4 motor/trans mounts and that's when I noticed the exhaust change, let me just say though, I'm almost 100% positive it is not rattle from stiffer mounts. With the cat, it cost me just shy of $500 to get it replaced the first time because the shop wouldn't let me bring my own cat. They came highly recommended from a few trusted car buffs I know so I don't think it was a screwed me kinda job, but it certainly wasn't a great cat. There's another local shop that I can bring my own to, but I don't know how much they will charge. Do you have any knowledge of how long/well the MagnaFlow cats last? They have a direct fit which is more expensive then a universal, but then I wouldn't need to pay a shop to do the work.

ezone

Wow I didn't see orange, and still don't.
Good eyes.

PMI

They are still not so expensive compared to OEM, I think.

Poor combustion, additives, or in the case of one car I used to own, burning coolant, all shorten the life of any cat converter. The Magnaflow cats should be above average, but they are designed for aggressive driving, not necessarily longevity. The two are related, but not the same.

EPA mandates that OEM converters on new cars must be good for 80K miles minimum, under almost any conditions. Aftermarket converters only have to last 25K miles under similar circumstances. This includes Magnaflow.

However, cat converter manufacturers selling universal converters online often cut corners, and justify it because their products are not tied to a specific make/model.

The original cat converter on my '96 Saab Turbo was still good at 210K miles of fairly aggressive driving. The OEM cat on a '95 Toyota I helped maintain lasted around 130K, and its Midas replacement, 80K by the time the car was scrapped due to rust.

I would expect 30~40K miles from an aftermarket "universal" or "weld-in" cat. Less if the engine is bleeding oil or coolant, or running race gas, or fuel additives.

M00n3at3r

I considered it more tan I guess. But I did run a thing of stp octane booster. Thought the noise was really bad knocking.

PMI

EPA on Catalytic converters.

http://www3.epa.gov/otaq/cert/factshts/catcvrts.pdf

A bit longwinded, but worth a read.

PMI

They look fine, but seem to have that orange tinge. They should be more grey than orange-ish if fairly new, and if the A/F mix is about normal.

Mad Dog Tannen

0420 is the code for smoking da reefer!

M00n3at3r

Unfortunately I don't have a code reader that will show me live data, just a generic one, so I can't check air/fuel curve. Now that I'm onto a new tank, maybe I will clean out the plugs and see what they look like after this tank. Just for curiosity sake. The cat article was an interesting read. I'm actually due for emissions so I'll take it in in the next couple days and see if I pass or fail then go from there. I read somewhere that Honda programmed really tight parameters for the cat and that's why they don't always like after market cats. Is that spark plug defowler trick just a redneck fix or is it a way to get around Hondas tight params so when it actually goes bad the sensor sees it?

M00n3at3r

So, out of curiosity, I took a look at the old injectors that were sitting on my work bench and looked them up on rock auto and noticed there is a difference in parts numbers between the injectors for the ex and the do, lx, and hx. To verify that I looked at Honda's website and searched under 2004 ex and 2001 lx, and again different, so I switched the injectors from the new engine for my old ones, along with the fuel rail, figured it wouldn't hurt, and get this, it drives amazingly. Idles smoother, revs faster, and runs quieter. As for the starting point of the thread, the P0420, I will have to wait and see if that comes back up, which it may but I will address it from there. As for performance, my little beasty is back and better then before. Going on a hunch I would guess the hx, lx, and do injectors are smaller? Maybe causing the engine to use more fuel to get what the computer believed to be the correct mix? If that's the case it would line up with my somewhat subpar gas mileage. Corse I did flog it pretty hard last night.

PMI

Great, you just saved yourself a lot of trouble, and potentially cost of a new cat! ...which is why I mentioned A/F ratio above.

Here's the backstory to what I think may have been happening:

Fuel injectors on EFI engines are rated by flow/time. Usually cc (cubic centimeters) per minute. But when you look up ratings, they are usually listed as something-cc, omitting the /min. A 200 cc injector is really 200cc/minute.

My EX w the D17A2 engine has 240cc injectors stock (I think).

The ecu opens and closes the injector to control the amount of fuel that goes into the cylinder, and under normal circumstances that length of time is adjusted based on the feedback from an O2 sensor to get a good air/fuel ratio.

If you install a higher flow injector, and unless the ecu is reprogrammed with a new fuel map, then the midpoint of the control range will be off, and the ecu can only make adjustments within a small range.

So, if you ran with much bigger injectors, the A/F mix would have been crazy rich, and the ecu would throw out codes related to the O2 sensors and emissions. Using an octane booster or race gas actually makes it worse (chuckle).

So the plugs look dirtier than normal, they show deposits related to the octane booster, engine runs rough, and the cat converter has a really hard time of it cleaning up the emissions. If you were to crack it open, I bet you would find similar tan-rust crap inside.

From badasscars.com:

...OK, prolly more than you wanted to know, but it seems like you care about the car, so, something to think about...

M00n3at3r

I do! No more octane booster for me!! I'm just glad it's back. Thanks for all your help, you too ezone.

ezone

Does this mean you did not install an engine identical to the engine you took out?

That would have been handy info to put in the first post.

M00n3at3r

Yes and no, sorry I didn't include that in the first post, it's a d17a, my old was an a2. Purchased from eBay with unknown miles and from an unknown model.

ezone

I would have expected the A2 would use identical injectors as the D17A VTEC. Maybe it sat long enough to gum them up?

At any rate, glad it's resolved.....now see if cat code comes back.