P430 on new cats (after upper engine repair)

[mckpaul]

Hey guys I'll try to keep this brief.

I had a P0305 misfire that I posted on here with several responses, long story short it's fixed, it was a bad exhaust lifter and wiped cam on #5. Got the truck back, runs great, drives great, all is well.

 

That said, prior to the repair, one of the things I did was replace the y-pipe/cats with a new set from AB Catalytic in Canada, direct fit aftermarket cats (the truck has 129,000 miles and ordering online was less expensive). These were put on about 4 weeks ago, and the truck was driven a limited amount for about 6 days with the bad lifter before dropping it off for the lifter repair.

 

So, I got the truck back, running great as mentioned, but about 2 days in it threw a P430. Scrolling through the scan tool I noticed the long term fuel trims were both running about -17 to -18 consistently, with little variation between idle, acceleration and cruise. I also noticed in the fuel system screens that the alcohol content was about 39%. I didn't make any changes and took the truck back to the shop. (Meanwhile researched alcohol composition levels). The truck is a flex fuel version but I've never run E85 (commonly sold around here) gas since I bought the truck in November. However, in the last 10 or so fuel fills I've been stopping at about 3/4 tank trying to get the monitors set, and I read where multiple partial fills can cause the alcohol percentage to get confused. He reset the alcohol composition, and it went back down to 3%, and he reported that the fuel trims went back to normal, but he didn't say he performed a fuel trim reset.

 

I took the truck and after an hour or so the P430 came back, and I noticed the long term trims had gone back to the negative numbers, just not quite as low...maybe -12 or so. The alcohol percent still looked OK after filling the tank, actually came up to about 6% (all the gas sold around here says "May contain up to 10% alcohol), so I cleared the P0430 and executed a fuel trim reset (last night) So far the long term fuel trims appear to be staying normal now (maybe +2-ish) and the short terms fluctuate around -1 or 2 and +1 or 2. Fingers crossed the P430 won't come back.

 

If I understand correctly, my 2010 Tahoe does not have a physical alcohol percent monitor device, and it does it automatically by crunching numbers after fuel level changes after adding fuel, correct?

I can't imagine one of the brand new cats was damaged with less than a week of driving 6 miles to work, had a misfire and bad lifter but wasn't running terribly. Is there any thing else that could create a P430 I can check for?

I'm not sure if there's anything in the engine top rebuild he could have done wrong that might cause that code, it's running beautifully. Could the cat have gotten maybe a little saturated while it was running rich before catching the high alcohol % and negative trims and maybe with some driving it'll dry out?

I looked at the downstream O2 sensor data, bank 2 did some fluctuation. I swapped the bank 1 & bank 2 downstream sensors trying to eliminate a bad sensor, but no change bank 2 still showed fluctuation.

 

I've read where exhaust leaks can contribute to P430, and considering the new cats were installed one weekend and then a week later the heads were pulled off,  it's possible there could be a small exhaust leak, but if so it's not audible.

 

 

 

[Jsdirt]

Someone will correct me if I'm wrong, but I think I recall reading a TSB on converter break-in, and that this code can happen until the cats have broken in. I doubt 2 days of rich running would harm a new cat, so long as the truck wasn't bucking & misfiring with the check engine light flashing that entire 2 day period.

 

Yes, these vehicles use an algorithm to calculate alcohol percentage. My '07 read in the 20% range until I got a bi-directional scan tool. I now reset it often. My fuel trims are similar (-8 to -15, varying), but the light has never been on. Something is borderline failing, and I can't pinpoint what it is at the moment. The monitors have not completed in over a year on mine.  Ever since the truck was new, I always run it down to E, and refill to the brim, until I see fuel in the neck. Just the way I've always done things, starting long before this OBD-II crap came about.

Edited July 25, 2018 by Jsdirt

[Jsdirt]

Ahh, my memory ain't as bad as I thought ... 

 

https://www.autoserviceprofessional.com/article/94135/cat-converter-break-in

[mckpaul]

Jsdirt you just took a load off my mind! I was messing with the misfire for 3 months and digging out, saving and printing all kinds of info, and actually while this has been a real pain in my behind, it's also been an education. At some point I remember reading about converter break in, told myself to keep that in mind if I decide to change the cats, but didn't save a copy of it. With everything else going on and finally just taking it in, I totally forgot about it. No doubt that's what the deal is with the code. Since the cats were put on, I've only driven highway speeds for short runs to take readings and absolutely have not driven 30 minutes at any time. I'll go do that break in drive per that article after work.

 

Thanks!

[Jsdirt]

No problem, Paul - glad to help. 

[mckpaul]

Well....the light is back. I tried a couple of converter break-in procedures, one was simply let the engine warm up for 5 minutes, then hold it at 2500rpm for 2 minutes. The other that jsdirt pointed me to requires driving at highway speeds for 25-30 minutes, stop and shut it off for one minute, then drive for 10-15 minutes more at highway speeds and then stop and shut it off for one minute. I performed both, the short one at startup before leaving the parking lot and the long one after .When I got off work (here in the Houston area) I had to drive for about 45 minutes of stop and go traffic to get out on a freeway where I could drive 30 minutes uninterrupted, but once I did I was able to drive about 70mph for 30 minutes, turned it off for one minute, turned around and did the same for 15 minutes, then had almost an hour of mixed driving getting home. So the cats should be burned in by now. I was pleased coming home since I had no light thinking I was done... and the darn thing came on again I the neighborhood.

 

At this point I'm suspecting a leak before the cat. The driver side (bank 1 that seems to be OK) has a flat plate type flange gasket, but the passenger side has a donut. A new donut was used when the cats were installed, but a week later the heads were pulled. I guess it's possible the guy pulled the exhaust manifold completely out and then re-used the donut, or may have just left the manifold attached to the cat and worked the head out since the exhaust manifold fasteners are bolts not studs, and made the donut leak. You'd think the head gasket set would have come with a new donut and he installed it, but who knows. Either way, I think I'm going to replace the donut, (which I know will involve breaking the driver side loose too and replacing that gasket) and while it's pulled down I'm hoping to have enough room to snake my gooseneck camera down and take a peek at the media. I think it's pretty unlikely, but I guess its possible that driving it for a week after the new cats were installed while I still had the bad lifter it could have been throwing off some extra carbon and got the new cat dirty. But, I only live 6 miles from work, all neighborhoods, never got on the freeway for more than 5 minutes after installing the cats to see if it made a difference. And besides that, the bad lifter was on Bank 1, the opposite side of this code for an inefficient cat. I may go as far as replacing the exhaust manifold to head gasket as well. If I do that I'm sure I'll be able to just look down into the cat.

 

Most of my life, for our 'second car', also known as the one I drive, I've bought used but nice and clean vehicles, usually with high mileage understanding that it's a roll of the dice, and understanding I'd just have to fix whatever happened. I've bought many cars that way and overall I've done OK. I'm starting to think this is the karma truck. patiently waiting until I'm 60 years old and then deciding to drag my butt through the dirt. I'm quite sure I saw a smirk on her grill last night as I closed the garage.

[KARNUT]

Well....the light is back. I tried a couple of converter break-in procedures, one was simply let the engine warm up for 5 minutes, then hold it at 2500rpm for 2 minutes. The other that jsdirt pointed me to requires driving at highway speeds for 25-30 minutes, stop and shut it off for one minute, then drive for 10-15 minutes more at highway speeds and then stop and shut it off for one minute. I performed both, the short one at startup before leaving the parking lot and the long one after .When I got off work (here in the Houston area) I had to drive for about 45 minutes of stop and go traffic to get out on a freeway where I could drive 30 minutes uninterrupted, but once I did I was able to drive about 70mph for 30 minutes, turned it off for one minute, turned around and did the same for 15 minutes, then had almost an hour of mixed driving getting home. So the cats should be burned in by now. I was pleased coming home since I had no light thinking I was done... and the darn thing came on again I the neighborhood.
 
At this point I'm suspecting a leak before the cat. The driver side (bank 1 that seems to be OK) has a flat plate type flange gasket, but the passenger side has a donut. A new donut was used when the cats were installed, but a week later the heads were pulled. I guess it's possible the guy pulled the exhaust manifold completely out and then re-used the donut, or may have just left the manifold attached to the cat and worked the head out since the exhaust manifold fasteners are bolts not studs, and made the donut leak. You'd think the head gasket set would have come with a new donut and he installed it, but who knows. Either way, I think I'm going to replace the donut, (which I know will involve breaking the driver side loose too and replacing that gasket) and while it's pulled down I'm hoping to have enough room to snake my gooseneck camera down and take a peek at the media. I think it's pretty unlikely, but I guess its possible that driving it for a week after the new cats were installed while I still had the bad lifter it could have been throwing off some extra carbon and got the new cat dirty. But, I only live 6 miles from work, all neighborhoods, never got on the freeway for more than 5 minutes after installing the cats to see if it made a difference. And besides that, the bad lifter was on Bank 1, the opposite side of this code for an inefficient cat. I may go as far as replacing the exhaust manifold to head gasket as well. If I do that I'm sure I'll be able to just look down into the cat.
 
Most of my life, for our 'second car', also known as the one I drive, I've bought used but nice and clean vehicles, usually with high mileage understanding that it's a roll of the dice, and understanding I'd just have to fix whatever happened. I've bought many cars that way and overall I've done OK. I'm starting to think this is the karma truck. patiently waiting until I'm 60 years old and then deciding to drag my butt through the dirt. I'm quite sure I saw a smirk on her grill last night as I closed the garage.

If you’re north of town near Conroe there’s a auto repair shop called Auto Pro. I’ve known him for over 40 years. He can fix anything and does exhaust too. He used by the auto dealers in the area his reputation is that good. He is not cheap, he charges the going rate, and backs his work.


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[mckpaul]

Well, to follow up on the P0430 code on the new cats, it's resolved. Don't have a definitive conclusion as to the exact cause of the light, but here's how it went down.

 

I was thinking of pulling the y-pipe down and pulling the exhaust manifold off to put a new gasket and properly torque it, if nothing else, to know there was no leak. As I looked over the engine, I noticed the far back manifold mounting bolt on the passenger side appeared to be missing, but could feel the broken off stud in the hole. Looking at the driver side, it was the same way. Since a shop had just had the heads off a week or two before, I took it back and requested all of the exhaust manifold bolts be present, even purchased a new set of Dorman exhaust manifold bolts and provided them to the shop to use. They were able to get the passenger side out, but the driver side required pulling the head again to get the broken bolt out. So I got the truck back hoping all would be OK, but the P0430 came back about 3 days later.

 

So looking at the exhaust manifolds again, I noticed the far back bolt on the passenger side was not one of the new bolts I provided (it was old and a different color), and didn't look like the bolt head was seated completely down on the manifold. I also suspected they probably just reused the manifold gaskets since they had just put them in a couple of weeks before. At this point I'm tired of dealing with someone else's work, and didn't want the same guy working on the truck that already got flagged for breaking exhaust bolts off on reassembly and just leaving them, so I bought new manifold and y-pipe gaskets, and tore into it myself. That last bolt that he substituted at the back of the manifold was not the correct thread, I think it was SAE instead of metric, but close. Luckily it was short. The thread damage on the head was only about 5 threads deep. But using that bolt, while torqueing the manifold bolts, since it was forced in it was really tight and not giving an accurate torque reading. So he had no way of knowing if it was tight enough to make a seal, and my guess is he just stopped in fear of it breaking off. I was able to back it out and clean up the hole with a M8-1.25 tap, and the replacement bolt is 30mm long (about 1-1/8") long enough to get a good bit into the deep undamaged threads. So I did get the new gasket in with all 6 bolts properly torqued.

 

Anyway, not being sure of the heath of the new cats/y-pipe, I also purchased a used y-pipe off a rear-wrecked '12 Sierra, so instead of taking a chance with the new cats and having to do the work again if it still reported in as bad, I just installed the used set instead of the new ones. So I'm 100% sure there are no exhaust leaks and I have used known good OEM cats in place, and all the monitors (except EVAP) have now set, including the cat monitor. The O2 sensor graphs on the scan tool look good so the problem is solved. I could have been an exhaust leak at the manifold, it could have been just the truck not liking the aftermarket cats, it could have been just a bad new cat on one side, I will never know, but I do for certain that the problem is gone, and that damn light is off. I just wanted to post that it was resolved since I started the discussion, and say thanks for all the suggestions and input!

[tbarn]

My money is on crappy aftermarket cats.

[mckpaul]

Yeah that's kind of what I was thinking. The aftermarkets were direct fit, and fit perfectly, but the cat canisters were a little smaller than the OEMs. I really wanted to put them back on after finding the screwed up manifold bolt thinking there was a good chance of a leak there, but really didn't want to change them out again if they had the same issue. I knew the used OEM's were good and would fly. Just makes it harder to sell the aftermarket set since I can't guarantee both sides are good. I'm still going to list them on craigslist, might get something for them.