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2005 325i Auto
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Discussion Starter #1
I'm really not taking the piss, I've seen the videos and the argument for/against.

Reason I'm asking is that I've had a "pending" 0420 code on my car and it's apparently running rich. But as a general rule it's OK when warm but still running a bit rich.

The car is a 2005 325i, 240,000kms. Auto trans. Precat O2's very recently changed with major intake/cooling refresh, and to be honest it's running very nicely with no codes and good economy. BUT, my fuel trims are dodgy in a way that suggests cat issues (as well as the one off code/message about cat efficiency).

I've read all the various articles on the net, and as usual you've got the people who've never done it talking. I'd really like to hear from people who've actually tried it, and hear about how it went for them, good or bad.

These are some points I've read, and how I felt:

1. It will attack your seals and injectors. I do doubt this one, as those seals/injectors are all rated for gasoline and I seriously doubt that thinners is any/much more aggressive. 4L in half a tank shouldn't hurt anything that way.

2. It will do nothing anyway. This I think is possible, and is why I'm asking for advice from people who have actually tried it.

3. It will mess up your sensors. That's a concern for me, as then we could have erroneous adaptations causing bad running. I doubt there's silicone in the thinners, but it don't know what else will know a sensor off its perch.

4. It worked a treat! There was enough videos and posts saying this for me to come here and ask. Admittedly most of them went by the name of Billybob, had huge buck teeth or other defects suggesting incest. But there were some who were a bit more steady and methodical.

Here's what I think...

The people who posted videos saying it worked didn't look like they were lying. I'll exempt Scotty Kilmer, because he just looks like he's completely tripping and doesn't actually know where he is. I always want to put a Thunderbirds outfit on that fucker and tie some strings to his hands so he looks more "natural".

I strongly doubt the thinners would damage the fuel system O rings etc myself. But I wouldn't say I'm so confident that I'd just go ahead and do it without checking into it more. People will mention acetone, but chances are there's already been some in your tank somehow. We had dodgy service station owners down here mixing all sorts into their fuel back in the day. Not sure, enlighten me.

I wonder if it's possibly effective before the cat fully blocks, while there's still a chance that the magical cleaning properties or whatever can at least get partway into the honeycomb and make a start.

I also wonder if it's not the recommended 150 mile drive that does it as well. After all, higher speeds/temps on cruise control for a couple of hours...clears the cobwebs.

Has anyone here done this with their E46?
 

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E30M3 Race F10 535 R1150Rt M Coupe
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I had a client that tried it. Waste of time.
Unsure of his application or methodology.
 

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2005 325i Auto
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832 Posts
Discussion Starter #3
I had a client that tried it. Waste of time.
Unsure of his application or methodology.
That's kind of what I'd expect. I can't see how much difference to the cat it would make, as it's combusted already. Might clean the intake a bit or something.
 

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2005 325i Auto
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832 Posts
Discussion Starter #5
I've known folks to try MEK. Super dangerous at a combustion temperature.
I think I'll try a 450km trip to Sydney at motorway speeds running 98 octane and see how that goes first. Yeah, that MEK is supposedly pretty bad stuff.
 

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BMW 320i 2002 e46 5spd manual RHD
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Do y'all have the cat emissions tests?(physical tests done on exhaust gases) If not, throw on a set of e36/e39 castless headers.. program the dme with euro 2 flash and be done with cat issues...
If you do however have them testing exhaust gases at emissions tests, then id say best to buy some free flow aftermarket cats.. either way, i have never heard of a successful cat cleaning product.
 

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2005 325i Auto
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Discussion Starter #7
Do y'all have the cat emissions tests?(physical tests done on exhaust gases) If not, throw on a set of e36/e39 castless headers.. program the dme with euro 2 flash and be done with cat issues...
If you do however have them testing exhaust gases at emissions tests, then id say best to buy some free flow aftermarket cats.. either way, i have never heard of a successful cat cleaning product.
I just want to keep it standard, and I don't want to spend too much.

I don't have to pass emissions here, so really it's just about whether it throws up a code or runs bad. I'll try a bottle of cleaner in the fuel and a good highway run for now.

In the meantime I'll wait for the gurus to look at my OBD Fusion logs, and see if there actually is a problem in that way.
 

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Tried it in both instances...not exactly a waste. But the treatments were to go on well past just one, and that's when I stopped...well maybe two. Anyways the conclusions you've drawn are pretty accurate. Buck teeth and all.
For me it was the codes indicating a problem. Not drivability. Maybe if I tried it longer I would have seen a substantial difference.

Sent from my SM-J727T using Tapatalk
 

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"Lacquer thinner" is a mix of chemicals- and that mix varies by manufacturer. It can be
far more aggressive, chemically, than gasoline, so I'd NOT put it into my car's fuel system.

oops, sorry, you wanted people who'd done it. I HAVE used Techron and BG44K, and both
do improve flow and patterns on first and second generation injectors. Dunno if they'd do anything for
ours, as they're pretty good.

Different suggestion: I know EVERYONE says the post- cat sensors 'don't do anythng'
but if you're starting to get indications that the DME thinks your cats are bad, they're
pretty inexpensive ($100 the pair, or so) to replace. I had a heater go out in one, so
replaced them both, and I don't seem to have the usual crop of sporadic random flow codes I used to...

just fwiw,

t
reduced
 

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When I rebuilt my head several years ago, I tried all kinds of things to clean the parts, including Acetone, Lacquer thinner, Mineral Spirits, and several other things. Full-strength, with soaking and scrubbing, most of them would not even touch the light brown oil residue in the cam valleys, much less the residue in the exhaust ports. The ONLY thing that worked on the exhaust ports was a Dremel tool with a small brass wire brush. I have a REALLY hard time believing any of them would do diddly for the fuel system, and even a harder time believing ANYTHING will have any effect whatsoever AFTER being burned in the combustion chambers. There is nothing left at that point but hot gasses. The original solvents are long gone. Really sounds to me like an old wives tale....
 

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the people’s mod
2004 330Ci 115k miles
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I would do an exhaust system back pressure test to confirm if cats are clogged or not, before doing anything else.
A borescope down the pre-cat O2 sensor ports may also reveal cat honeycomb condition.

If confirmed clogged, I would probably remove cats with bypass pipes or install headers.
 

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2005 325i Auto
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Discussion Starter #12 (Edited)
Different suggestion: I know EVERYONE says the post- cat sensors 'don't do anythng'
but if you're starting to get indications that the DME thinks your cats are bad, they're
pretty inexpensive ($100 the pair, or so) to replace. I had a heater go out in one, so
replaced them both, and I don't seem to have the usual crop of sporadic random flow codes I used to...
Yes, that thought has crossed my mind too. The thing seems to run fine, and economy and power are excellent (but maybe there's more to be had). I will try one of the commercial cat treatments in combination with a long highway run on cruise control first, then replace them after that.

I would do an exhaust system back pressure test to confirm if cats are clogged or not, before doing anything else.
A borescope down the pre-cat O2 sensor ports may also reveal cat honeycomb condition.

If confirmed clogged, I would probably remove cats with bypass pipes or install headers.
OK, sounds good.
 

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Discussion Starter #13
When I rebuilt my head several years ago, I tried all kinds of things to clean the parts, including Acetone, Lacquer thinner, Mineral Spirits, and several other things. Full-strength, with soaking and scrubbing, most of them would not even touch the light brown oil residue in the cam valleys, much less the residue in the exhaust ports. The ONLY thing that worked on the exhaust ports was a Dremel tool with a small brass wire brush. I have a REALLY hard time believing any of them would do diddly for the fuel system, and even a harder time believing ANYTHING will have any effect whatsoever AFTER being burned in the combustion chambers. There is nothing left at that point but hot gasses. The original solvents are long gone. Really sounds to me like an old wives tale....
I'm feeling you on that one for sure.

I've never seen anything that would just dissolve deposits in motors, even when applied directly. It really makes me wonder about all these fuel additives.

Not that it means much, but the exhaust looks to be in immaculate condition. No bumps/bruises, looks untouched. I will just try a long highway trip with the highest octane fuel I can get, and see if it doesn't do some of that self cleaning it's supposed to first.
 

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Reason I'm asking is that I've had a "pending" 0420 code on my car and it's apparently running rich. But as a general rule it's OK when warm but still running a bit rich.

I had P0420/P0430 on my F150.

Yes, my Ford and your BMW are apples and oranges, but the OBD II codes are the same, so let's go with it for a moment. I had some head work done and the codes came along afterwards. Turns out, an exhaust leak can give these codes. Maybe not your problem, but if you have been working on the exhaust system and now have the codes, doing a check of your work might be in order. For the Bonus Round, you should be able to fix an exhaust leak for free. My leak was where the exhaust system connected to the manifold, the gasket here is often called, "the muffler bearing." I went back to the mechanic and he put a socket on the bolts and gave them all another turn or two, problem solved.

You report that the car is "apparently running rich," but you do not mention the pending, or active, Rich code (P0172/P0175), therefore I would investigate the P0420 in isolation and avoid the tendency to do too much that only confuses the matter.
 

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Discussion Starter #15
I had P0420/P0430 on my F150.

Yes, my Ford and your BMW are apples and oranges, but the OBD II codes are the same, so let's go with it for a moment. I had some head work done and the codes came along afterwards. Turns out, an exhaust leak can give these codes. Maybe not your problem, but if you have been working on the exhaust system and now have the codes, doing a check of your work might be in order. For the Bonus Round, you should be able to fix an exhaust leak for free. My leak was where the exhaust system connected to the manifold, the gasket here is often called, "the muffler bearing." I went back to the mechanic and he put a socket on the bolts and gave them all another turn or two, problem solved.
Certainly a point to be considered, thank you.

I very much doubt a leak, as I've got an ear for that and no one seems to have touched it ever. If I had been in there though, yes I would go back and recheck my work.
 

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Certainly a point to be considered, thank you.

I very much doubt a leak, as I've got an ear for that and no one seems to have touched it ever. If I had been in there though, yes I would go back and recheck my work.

I couldn't hear it. And since exhaust is a positive pressure, then gases escaping didn't seem like it should be an issue for the CAT to care about. To be fair, my F150 has a manifold that bolts to the engine, and the CAT is further downstream, but your BMW has the CATs built into the exhaust manifold, so the leak (if there is one) would be where the manifold bolts to the head, and the aluminum comes into play as a danger zone.
 

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Discussion Starter #17
I couldn't hear it. And since exhaust is a positive pressure, then gases escaping didn't seem like it should be an issue for the CAT to care about. To be fair, my F150 has a manifold that bolts to the engine, and the CAT is further downstream, but your BMW has the CATs built into the exhaust manifold, so the leak (if there is one) would be where the manifold bolts to the head, and the aluminum comes into play as a danger zone.
All right. I'd better look into that possibility as well. Cheers for that.
 

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All right. I'd better look into that possibility as well. Cheers for that.

Just trying to help. I'm not one to promote chemicals, my 65+ years has taught me that they are just a band aid.

This might be one of those times when OBD Fusion should be used to build you a chart of the actual sensor activity. You can go on Amazon or eBay and get an ELM-327 module, then go to the app store for your phone and get OBD Fusion for 10 bucks. You get graphing capabilities of every sensor.
 

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I'm with Ray on this one. I'm rebuilding an an engine from another make and was reminded while cleaning the head's carbon deposits how crazy difficult it is. I even returned a pricy gallon of the legendary Berryman's carbon cleaner and discovering that like Compound W, Oven Cleaner, and Rachel Welch, it's not like it used to be when it became a legend. Watered down. The only way I could see any compound cleaning your cats would be if you ruthlessly flooded the engine to near stalling with the product so it's splashing through as a wet mist into your exhaust system, and then I'd be worried about the grundge it's moving from the exhaust manfolds that is now flowing like lava to your already clogging cats.

I know you only wanted to hear from folks who've actually tried it, but thought it might also be worth hearing from folks who have been in the next lane over from the " cleaning with chemicals lane" with a wire brush in our hand that grasp the magnitude of that work and the truth of it working. Many people lay claims to things working online because they've become mentally invested in it since they did it, and if they hold their head just right, and the lighting is perfect, and the only second opinion they got was their girlfriend - that paint job they did in the garage looks "super dooper awesome, man - you should try it!..." Cough...
 
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Fwiw, 50s kid has a YouTube video where he tries cleaning the catalytic converters by soaking the headers in a 5 gallon bucket filled with lacquer thinner or some other solvent. I don't think it did much.
 
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