Bad Cat's?
 

Hey X5'ers,

I've been getting P0420-P0430 codes for a while and been having issues with fuel trims and recently discovered I had an issue with the wiring for my MAF. I would see high numbers when idle, 7-18g/s and up. I replaced the wire and now seeing around 4.1-4.6g/s. I was getting lean codes too which havent shown up since the wire repair.

I used cataclean twice an I do think it helped a little. at a stationary 2000 rpm when I monitor the downstream sensors, bank 1 looks a little better than bank 2. When driving they the voltages get pulled down on both, maybe not as frequent as post o2 sensors. If I maintain a 2000 rpm driving, it looks the almost the same as idle. any acceleration, deceleration will have them jumping around, just not the same as upstream.

For now I haven't triggered the cat efficiency code in bank 1 but I did trigger bank 2 last night after a few days of test drives and the second bottle of cataclean. Usually P0430 would appear even after 20 miles of driving.

Now the fun part. I put a mini camera inside the upstream O2 sensor holes and I see some carbon buildup. bank 1 looks better than bank2. Bank2 looks like it has a good amount of buildup.

I was thinking about using a product like the Motor Power care catalytic cleaner and have spent a few days watching all kinds of cleaning methods and reading peoples opinions about the task, good or bad. I just don't feel like my cats might be toasts just yet seeing that there's a good amount of carbon buildup.

Attachment 83606
https://www.youtube.com/watch?v=FoBbi6kOwFc

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Basics first. High fuel trims could have fouled your plugs. How old are the plugs? Have you looked at them? Leaking fuel injectors can cause problems too. What's the mileage on parts? Any other recent maintenance?

At about 190k miles I was having high fuel trim end up replacing MAF to resolve but on wife's m54, had Lowe efficient cats and used defouler to smooth out the sensor feedback and get a couple more years out of the cats.

Watch the pre/post volts on a graph. The post cat should not track with the pre cat voltage. If it just slightly follows the cats are worn and a candidate for defouler. If they swing like pre cat they are end of life.

I'm at 144K now and yup I have the defoulers on. The short ones so it still does pick up the emissions.

Did you see the video, seems like some improvement cant be had if whatever is build up on it can be removed. Especially bank 2.

I do use Scanmaster ELM and I have torque in my Android radio with a nice dashboard of my O2 sensors. Scanmaster is more accurate and I like the old version with 2x2 graph display. This is how I know i'm almost doomed. LOL

After this weekend and seeing what the cat and O2 sensors looked like, I am ready to buy new plugs. I did clean the sensors before inserting. I made and attempt earlier but got distracted. But I havent changed them since 2019 and that bad MAF wire was happening back then too and I did replace the MAF at that time. The problem was intermittent and even when I suspected the wire, it improved then got out of whack. I finally changed the plug and fuel trims don't go nuts, LTFT is around 2-3.0ish, not throwing lean codes.

Any suggestions on plugs? I don't remember what I used in 2019.

So while I was out today I wanted to give the X another run on the highway. I started with a long idle rev of about 2500 rpm for a minute because of the lifter ticking I mentioned in another post to you. I didn't hear it on startup this time but I was reading something about a procedure to run the engine at 2500-3000 for 3 minutes for lifter issues.

On my highway drive in sport mode I was hitting about 4000 rpms for as long as I could. I never run my vehicle this hard. after that I was monitoring on ScanMaster and drives at 2500 rpm showed the Bank 2 doing a little better. Bank 1 too. I figured after the two bottles of cataclean and fixing that MAF wire its best to just drive it on the highway and try to burn up any excess carbon I can. I did order OEM plugs and they are on the way.

I don't see any issues when idling. and even idling at 2000 rpm it doesn't match pre cat. Highway driving is a little different but here is 2500 rpms on the highway.

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I read that the voltage on up/down O2 sensors pulls down when you break. I didn't know that.

Sorry. I didnt answer all your questions. I ordered plugs, they are on the way. I will post pics when I pull them. I havent done any major recent engine maintenance. I am not sure of the condition of the fuel injectors. I would like to check/clean them or replace. I want to replace my fuel filter because I have an evap leak and its not in the front, but I suspect its the little rubber evap hose attached to the fuel filter. filter never been replaced. put 2 new ignition coils in recently, others are a few years.

The O2 sensors are not old, replaced last year or two.

I replaced my spark plugs. The three in the rear look worse then the three in the front.

After clearing my adaptations and took a drive, my fuel trims have improved. Before I was seeing LTFT 2.7-3.9 after a highway drive. now I am seeing 1.56 on Bank1 and 2.34 on Bank2 of LTFT.

When I drive around locally, it drops back to 0-.71ish for each bank.

Here are all of them.
Attachment 83614

These are what looked liked the worst two.
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