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Ok so I've been chasing these problems for about 3 months. Backstory bought a used 2005 Acura RL in April no cel car appeared perfect . I drove the car around 5k miles that first month no problems other then car seemed to be run out of fuel before the gauge got completely to e and occasionally the check emissions light would come on , stay on a day and go off. Ok one day I had drove approximately 300 miles mostly interstate and stopped idling in a parking lot for maybe 10 min car starts idling ruff basically acting like it's running out of fuel, hit the gas and it just bogs, I was within sight of a gas idled over put fuel in it, gauge was just under half a tank when this happened car goes back to running fine drove 200 more miles that day no problem. My thoughts were bad fuel maybe water in the tank.The next day added some Lucas fuel treatment drove about 30 miles no problems cut car off for maybe a hour got back in got into traffic jam car bogs at idle will barely run but never completely quits fuel gauge over half tank pull into gas station put fuel in it no difference. Car would basically run normal for the most part as long as you didn't have to stop at red lights. Drove it to nearest napa rebuilt fuel pump in the parking lot. No change. Check engine light never came on during all this. Drove to advanced auto scanned it po171 po430 battery died in parking lot called wrecker. Wrecker shows up 5 hours later puts jump box on it fires up and runs like new. Towed it to shop that specializes in Honda Acura in Atlanta no cel he had Honda/ Acura scanner plugged in driving around let it idle for hours never showed code never bogged, he kept it 3 days couldn't find anything wrong said fuel trims looked perfect. I picked it up took it to exhaust shop and had the 3rd catalytic converter removed straight piped it cel did stay on after that po430 .Drove it maybe 300 miles before it did it again after idling maybe 15 min not nearly as bad as the last time put fuel in it went back to running fine. Started basically living around it between then and now it actually quit doing it for the most part over the next 5000 miles although I did quit leaving it idling for more then a few minutes. Scanned it a couple of times only code is p0430. I replaced the battery no cel then cel came back on 120 miles later car running fine. I ordered a Bluetooth OBD2/ torque pro app scanned codes p0430 cleared code immediately car bogs idle over to pump add fuel/ runs like new. Stft and ltft must have reset with battery change or because I monitored them over the next day and can tell it's relearning the ltft again more on this in a min. Drove the car maybe 200 miles no problems ltft running around +12.5 on bank 2 about +9 on bank one pulled up to store car idling with half tank bogs add fuel runs fine. I've been constantly monitoring this for a couple of weeks ltft settled around 12.5 give or take depending if you're doing alot of idling or driving 70 or whatever rpm doesn't really effect it alot. So yesterday I'm taking my wife around to do all her stuff car is running fine a/f has been at 14/7 this whole time. While I'm waiting on her to come out of bank I notice my a/f has went to 9/7 ish car is still running fine drinking more fuel obviously idling fine. Ok so I thought open loop but the the scan says it's still closed loop the fuel trims are still active like it's closed loop and I can still see all my o2 sensor's functioning. So how could it be in open loop with the fuel trim still active? Is there some kind of protection semi closed loop where it just went rich to protect but still uses primary o2 sensor's to keep it at richer mixture? Will a bad secondary 02 sensor cause this? Fuel trims seemed to be heading down since this. I'm fixing to replace both secondary 02 sensor's to eliminate that.
Finally figured it out. The fuel tank not venting . I was suspecting this and after crawling all over it looking for vacuum leaks today, I decided to take the fuel cap off it. To keep a long story short it's fixed fuel trims are perfect after a couple hundred miles no cel.
Ok think about trying to pour gas out can without opening the vent or shot gunning a beer. As you draw fuel out of the tank you create internal vacuum restricting flow if you have no vent eventually all flow come to a stop. Basically without a vent your as vacuum increases your slowly starving the whole system more and more until you take the cap off release the pressure and start the process over again. I can take some pics screen shots of the fuel trim tomorrow if you would like to see them . They went from positive 18ish percent stft and ltft both sides to basically 0 percent both sides st and lt in about 200 miles so far. My P0430 did come back so that converter is probably gone because the sensor looks good on graphing compared to the other one. The lean condition is gone and that's what matters. I can pull that sensor out of the exhaust stream and fool it. I have 2 new ntk secondary sensor's in the back seat.
I'm actually going to either gut those two top converters or cut them out and weld a piece of pipe in basically pcd just haven't had time to take them off to do it so those cat below efficiency codes don't matter to me anyway. I don't have to pass emissions anyway. 3 converters , 4 resonators and 2 mufflers is dumb anyway. All motors new or old diesel or gas like to breathe and like plenty of unrestricted fuel to drink. All this emissions crap is nothing but problem causing junk. I will say this had me stumped for awhile. I've been a mechanic first cars now diesel for a very long time. I will post some pics of the fuel trims tomorrow. You can see what they were before in the freeze frames I posted earlier.
Here are some screenshots I took randomly this morning at different speed, rpm probably load like pulling a hill or just cruising. Only difference from the earlier ones is the gas cap is off.
Ultimately the way I fixed it was I just removed the spring and plunger out of the gas cap allowing it to breath freely and it's obviously enough resistance to keep the no gas cap light and code from coming on because I cleared it a couple days ago and it's not pending or anything. I like my stuff to have unlimited flow if I want to regulate it I will do it on the other side of the pump. I fixed me up a little air filter setup today will post a pic in a min.
It's the bigger 9 inch long universal filter would've bought the k&n but I needed the reducers that come with these brand I have used both brands same size on 7.3 power stroke diesels ones really as good as the other from my experience. Filter # is spectre 9732
You are providing limited information, but engine is at 17stft on both banks, there is nothing great about it. Running lean, so it is dumping fuel. Mileage should suck, also there is great chance you are killing or already killed CATS.
That pic was probably took during a throttle blip definitely not running lean. When you blip the throttle just a little stft will jump then settle back down. You can think what u want I could go get another pic after holding throttle steady and stft will be barley anything. Car is getting 28 mpg on the freeway about 24 in town. I'll get you another pic if u want here's one at idle from this morning. Stft is very sensitive to blips if I stomp it it's going to go to zero it fluctuates depending on load. If you let completely off it's going to zero out. Remember I'm driving down the rd screenshoting so holding my foot steady isn't exactly easy. If the car was dumping fuel the long term trim would be high.
That pic was probably took during a throttle blip definitely not running lean. When you blip the throttle just a little stft will jump then settle back down. You can think what u want I could go get another pic after holding throttle steady and stft will be barley anything. Car is getting 28 mpg on the freeway about 24 in town. I'll get you another pic if u want here's one at idle from this morning. Stft is very sensitive to blips if I stomp it it's going to go to zero it fluctuates depending on load. If you let completely off it's going to zero out. Remember I'm driving down the rd screenshoting so holding my foot steady isn't exactly easy. If the car was dumping fuel the long term trim would be high.
2.5 hour trip this morning. O2 sensors alot of factors effect stft has to be used in conjunction with ltft. Lt will give you a better idea of what's going on all the time and overall.
Here's another zoom shot. If you think I'm wrong please tell me your train of thought on what's going on here. There's no denying the original lean condition is gone just compare the fuel trims in the freeze frame to the current ones the difference is not comparable. I'm always open to suggestions.
If there was a lean condition when u see those peaks at full throttle the stft would sky rocket because the demand for fuel would go up, instead you see the stft go to zero because your bypassing your 02 sensor's at that throttle position basically in open loop. My way of thinking is basically your 02sensors are constantly making fine trim adjustments in your stft while at cruising speeds taking your mixture from lean to rich. Maybe I'm wrong but that's my take on it.
trims are all over the place. Engine should not run like that. I just retuned my mdx my trim variation is +-5. When i was experimenting with my 3.5' CAI I was getting similar fuel trim readings, but since RL don't have MAF sensor....Go back to stock air box and check if there is any improvement.
I will repeat my self, you are running lean and dumping fuel.
They were the same with the stock air box no difference. How do u explain the negative ltfts? How do u explain the difference when the cap was removed no codes present since no driving issues . If you don't see the difference in the freeze frame and now then something is definitely wrong. Fuel mileage is perfect. I'm not saying I disagree with the fact the stft is bouncing but I do disagree that it's lean because the ltft is showing opposite of that and I put more faith in lt then short. The filter made no difference in the charts I may have one from before I put it on I would have to look.
Read the part about stft sweeping with o2 sensor's. If you had a overall lean condition your ltft would show it. Your stft is constantly changing depending on engine load, rpm, air temperature, o2 voltage and I'm probably forgetting a few things. Trying to tune to constantly changing conditions will not work in my opinion you have to tune to over all condition which is identified by ltft.
