jross20
New member
First off I want to apologize for my long absence for a few weeks... I don't know if I've shared it with anyone but my grandfather was diagnosed with ALS and it has been incredibly hard on us. Please keep him in you prayers if you can.
Full story below, but for those who just want the results, I added a TLDR at the bottom.
So, probably for over 6 months now I've been having to buy premium gasoline, because anything less would cause the engine to ping horribly on the slightest bit of an incline. Originally when it first became bad, it was actually so bad sounding that I literally thought the engine (V6) had exploded or something.
I had changed the spark plugs, at the timing check, had two mechanics check it out all to no avail. It wasn't running lean, if anything it was rich. Just made no sense...
Stepping back in time for a minute... Slowly, over the course of about a year or two, which of course was prior to the pinging, I had gone from averaging about 19 to 19.5 mpg for my typical work week drive, down to 18.5 to 19, then 18 to 18.5, then 17.5 to 18, then 17 to 17.5, all the way day to 16, etc... You get the point. Power was also, in my opinion, very lacking and felt like she always bogged down. All the time, not a single code, nothing at all that made any kind of sense that I could figure out...
So anyway, now fast forward to about a month ago, a gearhead friend at work who likes messing around on BMWs and Mercedes said "if it seems hot for no reason and doesn't want to accelerate, you should probably replace the catalytic converter at that age". I always been curious if this could be a possibility, but I presumed it would have set off a code or been more obvious.
After that, I went to a small, somewhat sketchy muffler shop, where the lead guy messed around with it for a bit and told me that while there were no codes he said it was excessively hot in his opinion.
At that point, I said "f it", I'll replace it and see what happens.
Well about $800 later, I'm driving around testing the new one and as far as I can tell it made literally no difference to the temps at all... Not only that, it's way louder than the stock. I was pretty frustrated and told myself that I would just get the other one put back on and try to sell off the other one to recover some of the money...
Well, this is one of those times where it paid off to be lazy. So one of the first things that I immediately noticed is that two fill ups later, My gas mileage had completely tanked. The first whole tank on the new cat was like 15 mpg. "Damn, my poor truck" I said to myself... Haha.
Now for the next part, I honestly cannot say what made me think to try changing to non-premium, but I decided to try it. The next tank I went down to mid-grade, all was well. So the next tank after that I went down to regular, all was well. No at this point I was still skeptical, so I kept doing regular gas for the next few tanks, and sure enough the pinging was totally gone. They're always certain spots, small hills, where if I purposely tried I could always get her to ping but even in these areas she was silent now.
So here's the next thing, ever since then my mileage has slowly but surely started to come back up. Again, I pretty much always drive the same exact route to work. Now the only thing that's weird is that while it's consistently up now, it does still fluctuate a bit wildly. So like I had three fill ups in a row where I'm getting 18.5, and then the next one is like 16 mpg. Then, the next one is 18 again.
I presume that all of this has to do with the ECU relearning with the new cat? But the weirdest thing is that I really don't understand why the new cat fixed the pinging. Mainly because I presumed that if the air fuel mixture was wrong that it would be lean, not rich. And when I say Rich, I mean long-term fuel trim would always be like plus 5%. So not crazy or anything.
TL;DR:
I replaced my catalytic converter trying to solve the heat problem, inadvertently fixed the pinging problem. Gas mileage greatly improved but it's still a bit volatile. For those who are curious, I got one of those MagnaFlow direct fit cats for about 600 and some change.
Full story below, but for those who just want the results, I added a TLDR at the bottom.
So, probably for over 6 months now I've been having to buy premium gasoline, because anything less would cause the engine to ping horribly on the slightest bit of an incline. Originally when it first became bad, it was actually so bad sounding that I literally thought the engine (V6) had exploded or something.
I had changed the spark plugs, at the timing check, had two mechanics check it out all to no avail. It wasn't running lean, if anything it was rich. Just made no sense...
Stepping back in time for a minute... Slowly, over the course of about a year or two, which of course was prior to the pinging, I had gone from averaging about 19 to 19.5 mpg for my typical work week drive, down to 18.5 to 19, then 18 to 18.5, then 17.5 to 18, then 17 to 17.5, all the way day to 16, etc... You get the point. Power was also, in my opinion, very lacking and felt like she always bogged down. All the time, not a single code, nothing at all that made any kind of sense that I could figure out...
So anyway, now fast forward to about a month ago, a gearhead friend at work who likes messing around on BMWs and Mercedes said "if it seems hot for no reason and doesn't want to accelerate, you should probably replace the catalytic converter at that age". I always been curious if this could be a possibility, but I presumed it would have set off a code or been more obvious.
After that, I went to a small, somewhat sketchy muffler shop, where the lead guy messed around with it for a bit and told me that while there were no codes he said it was excessively hot in his opinion.
At that point, I said "f it", I'll replace it and see what happens.
Well about $800 later, I'm driving around testing the new one and as far as I can tell it made literally no difference to the temps at all... Not only that, it's way louder than the stock. I was pretty frustrated and told myself that I would just get the other one put back on and try to sell off the other one to recover some of the money...
Well, this is one of those times where it paid off to be lazy. So one of the first things that I immediately noticed is that two fill ups later, My gas mileage had completely tanked. The first whole tank on the new cat was like 15 mpg. "Damn, my poor truck" I said to myself... Haha.
Now for the next part, I honestly cannot say what made me think to try changing to non-premium, but I decided to try it. The next tank I went down to mid-grade, all was well. So the next tank after that I went down to regular, all was well. No at this point I was still skeptical, so I kept doing regular gas for the next few tanks, and sure enough the pinging was totally gone. They're always certain spots, small hills, where if I purposely tried I could always get her to ping but even in these areas she was silent now.
So here's the next thing, ever since then my mileage has slowly but surely started to come back up. Again, I pretty much always drive the same exact route to work. Now the only thing that's weird is that while it's consistently up now, it does still fluctuate a bit wildly. So like I had three fill ups in a row where I'm getting 18.5, and then the next one is like 16 mpg. Then, the next one is 18 again.
I presume that all of this has to do with the ECU relearning with the new cat? But the weirdest thing is that I really don't understand why the new cat fixed the pinging. Mainly because I presumed that if the air fuel mixture was wrong that it would be lean, not rich. And when I say Rich, I mean long-term fuel trim would always be like plus 5%. So not crazy or anything.
TL;DR:
I replaced my catalytic converter trying to solve the heat problem, inadvertently fixed the pinging problem. Gas mileage greatly improved but it's still a bit volatile. For those who are curious, I got one of those MagnaFlow direct fit cats for about 600 and some change.
