tartilc

So I've been doing a lot of research and since I have started to put a lot more miles on my TL I decided it was time to give it some attention. Prior to touching anything I had no CEL or any actual "issues" anyone could detect with driving the car but I really have been getting poor gas mileage (I know, I know there are tons and tons of threads on this and I've read most of them so I won't waste your time ).

I also noticed the car was slightly aggressive with the downshifting (just enough to be annoying) like when I'd brake I'd have to adjust my braking to make it stop smoothly. I would press the brake pedal, then the car does some engine braking so it slows down more than I need, then it goes back to coasting. I read that this could be caused by an IACV not keeping the rpms up when slowing down like it should.

Yesterday I decided to clean my EGR and throttle body, I decided to leave the manifold on the car just because (I hadn't thought to remove it to help keep the deposits from going through the cat and stuff). The EGR port was completely filled with carbon deposits, got it looking nice. I also cleaned the passageways in the cover, cleaned the gasket (made sure to put it on again right side up), cleaned all six holes. Afterwards the car sputtered up and spewed out a ton of white smoke for at least 30 minutes. The idle went crazy going up and down for a while and then went back to normal. Took it out for a spirited drive afterwards to make sure I got all the deposits out and all.

Today when I drove it in the morning it drove like normal but still had the engine braking oddity, but about an hour ago the idle went whack again and both the VSA and CEL came up. Turned off and restarted and it went back to normal. Decided to order a new IACV for $25 with a 10 year warranty from AM Parts (I was going to go with the intermotor one but since this has a 10 year warranty and is about a fourth the price I decided to chance it) and a throttle body gasket. Also got a set of NGK 6441 Iridium IX spark plugs for $33 that I've been kind of delaying for a while.

***TLDR Part***

Now onto my actual question (sorry this sort of turned into a longer post, wanted to give more information). Since I'm all about getting better gas mileage and am doing all this maintenance anyways, and I read a bunch of posters saying they got way higher mpgs after doing it, should I replace the O2 sensor? (honestly my car has 200k+ miles and I want to do it anyways too) The bigger question is which O2 sensor do I replace? I think there are three on my car, one on the front bank before cat, one on the rear bank before cat, and one after cat. I have no CEL or codes. From what I've read I've deduced that there would be no point in changing the one after the cat. Do I have to replace both the front and back upstream ones? One post said only the bank 1 upstream one is really important for fuel trims but I don't know what information to trust... I found Denso part number 2344727 for $45 shipped from RockAuto listed as the Upstream O2 sensor for my car, is this the right one?

Last little concern, I think I may have a slight exhaust leak coming from where my headers are welded to their flange or near the flex pipe area, is this something I should be really worried about? Would this effect the performance of the O2 sensors in any large way?

Thanks for reading!

FreeIsGood

Funny. I just replaced my o2 'upstream' sensor this weekend and did a little write-up. I highly recommend you purchase a scanner so you can see if it detected something specific. A 2001 TL only has Bank 1 with sensor 1 and sensor 2. Nothing else.

If you want to read my write-up, search for "p0131 oxygen sensor"

Also, I was about to buy the O2 from rockauto but found amazon to be quicker if you got Prime. Also get the lucas fuel treatment 32oz from amazon at $9. Super great bargain. you'll only need to pour 6oz and save the rest. I'm going to treat it every 5000 as my car as over 220000. I should replace my sensor 2 but needed to make sure the check engine cleared before messing with other things which it did.

Chojun

My '03 is about to roll up on 189K miles. I watch my mileage very carefully and am averaging out at 30MPG with an occasional spike to 32MPG depending on how much I drive around town as opposed to commuting to work. With that said, I really haven't done any critical maintenance ( ) at all ( ) and so I have a huge laundry list of things to catch up on. So she's been very faithful to me (except for transmission rebuild in '11 at 96K miles). I mean I've replaced none of the sensors and (I'm ashamed to say it) am running on the original timing belt.

Make sure you're using high octane fuel first and foremost (a big mistake lots of people make with their TLs). You can treat your fuel 1x or 2x per year with Seafoam (1 bottle per slightly-less-than-half-tank). Using anything other than minimum 91 octane will eventually result in a clogged EGR.

Additionally, if you don't have Honda DW-1 in your Transmission then do a 3x3 drain/fill to get yours replaced with the recommended fluid. It could boost gas mileage.

Your O2 sensor 1 is the one that influences fuel/air mix. O2 sensor 2 monitors proper functioning of your cat. Definitely replace your IACV. You may consider getting your valves adjusted. Also check your cat to make sure it isn't messed up. Get a rubber mallet and tap on it and if you get any crunching or rattle noises inside it then you need to replace it. Also I'm assuming that you've already checked your air filter.

tartilc

Thanks for the tips! I was getting at most 20mpg average with 70/30 hwy/city driving on 93 octane gas :/ I just cleaned the EGR and so far have gotten 75 miles out of a quarter tank (I would need to finish the tank and refill though to be certain if I'm actually doing better now though), prior to it I got to only about 50... I also put 1/3 can of seafoam in the tank, but when I bought the car I had done a full seafoam treatment (vacuum hose, oil, and gas tank). I bought more DW-1 to do a 3x3 later but currently my fluid seems to be a nice healthy red color.

Darksyne

Dude! It's 2017 how is that timing belt even holding itself together after a decade and a half XD

Chojun

I really hate publicly admitting that Especially when I know better...

Darksyne

Honestly you should feel proud about it I mean it's been nearly 15 years and 200k on one timing belt. That belt has broken all the rules as it is haha. But in all serious though it doesn't mean that it's immortal and you should get it change before it brings doomsday to your engine.
The Acura dealership I go to quoted me $1400 for the job but I'm sure a reputable mechanic can do it for less than a grand if you bring your own parts like I did.
If you do get it replaced you gotta show us pictures of the old belt and water pump though I'm just as amazed that it's not leaking. Would make an interesting thread ;o

murky

The manual calls for 4 times drain/fill.

grandlaker

Regarding the comment on only using higher octane fuel, my '01 TL is at 298K miles and from day one( I bought car new) I've only ever used 87 octane. All original O2 sensors still in car and get 30 mpg consistently.

Iggy

Which manual are you referring to?

Darksyne

How often do you drive spiritedly? Ever put put and tried to see if you could notice a difference? I've been putting premium in the car since day one and the engine still runs like new, all the injectors and O2 sensors are good and no problems with the Cat.

tartilc

I need to know your secret. Mine is an 02 Type-S but tonight I got the highest gas mileage I ever got so far tonight, 272 miles when the gas light turned on, haven't hit E just yet though, I expect to reach about 285-290, divided by 14 gallons means I still only get 20mpg Previously I was doing way worse, yet you get a whole ten more mpg than my best or over 400 miles on a tank!

Karanx7

iTrader: (2)

If that's highway miles, then something is wrong with your car. You should be getting more than that for sure. But for 100% city driving, that's about right.

Also, keep using Premium gas. The guy using 87 octane has a lower compression ratio than you. Also, he's lame for using 87.

Chojun

Yep Hondas have high-compression engines and need 91 octane minimum.

Also the brand of gas that you buy could have a huge impact on your gas mileage. I used to get gas at Chevron for a long time but noticed that Maverik (convenience store chain based in the west) gives me much better gas mileage. So try switching to a different gas station for a while and see if that helps. But either way, if you're not buying top-tier gas with the cleaning additives then you'll need to do a seafoam treatment up to 2x per year.

Another thing to watch out for is RPMs. When my Transmission was about to go bad I noticed a huge drop in gas mileage (50 miles per tank drop) and higher-than-normal RPMs at freeway speeds. So if you're getting poor gas mileage it's more than likely your car telling you that something's wrong.

tartilc

I don't usually pick and choose between gas stations, I just go with whoever has 93 available for the cheapest (sometimes there are huge differences like 50 cents more per gallon). I have used seafoam on the car also a couple times so that should be fine. How should my RPMs be on the freeway? I seem to stay around 2100ish at 75mph although I can't say for certain as I haven't paid too much attention to that.

tartilc

Update to this. Anyone considering buying a cheaper IACV than the Intermotor one, just don't. Despite advertising a 10 year warranty, the one I bought was crap. Installing it made the car undriveable and threw a different code, revving it made it misfire and die out before hitting 2500rpm. I decided to clean and reuse my old Denso IACV and the problem was resolved and the car drove perfect again, no more crazy idle going up and down or annoying engine braking. The new spark plugs helped a bit too I think. I'm unfortunately still only getting about 300 miles on a tank though. I bought a new Denso front O2 sensor but I'm going to wait until I fix or replace the headers before installing that. Hopefully that will be the fix for the gas mileage.

One thing though, my car really doesn't like taking off from 40mph. Is this normal? What I mean is going steady 40mph and then flooring it, it's as if the car just ignores what I want it to do and stays in 5th or maybe downshifts into 4th (can't really tell). I threw it in 3rd using the sportshift and gunned it from there too with not much better results, only way to get it going quickly from 40 was to drop it all the way into 2nd before dropping the hammer and then quickly upshifting into 3rd. This seems like it'd be hard on the car though, is it just really that lazy from 3rd/4th and 40? From a dig its fine and it's also great from 60-65ish on.

Chojun

Cruising at 40mph in D5 you'll be in 4th gear with TC locked. Transmission shifts into 5 at 45mph, cruising under low engine load. Driving in D4 will disable the TC lockup mechanism (which for me enables smoother shifting at speeds less than 40mph). The J32 just really doesn't have a lot of low-end torque unless VTEC is engaged, which really only occurs at ~4K RPM. I've noticed that sport shift mode causes the ECU to change when it engages VTEC along with how downshift behavior occurs when the throttle is in a more wide-open state (but not necessarily fully wide open). Without sport shift mode the ECU tends to keep the transmission in its current gear.

Now with all that said I did notice a number of years ago a lack of power when flooring it on the freeway. Whilst driving on the freeway on a somewhat steep grade (I-80 east to Park City, UT) I was barely able to keep up with traffic moving at freeway speeds. Later I found the problem to be a clogged air filter along with old/worn spark plugs. Definitely don't write those off and be sure to replace your plugs with nothing other than NGK Irridium IX plugs.

tartilc

I'll check my air filter to see if it is attached properly at the end of the CAI tomorrow (its a newer filter so I don't think its clogged just yet). I recently put in brand new Iridium IX plugs on the car as well. I'll also try driving it in D4 and doing a couple pulls. Do you know if kickdown (gas pedal to the floor) works in sportshift mode?

Chojun

I haven't driven in SS for a long time now but I believe it only works in 2nd gear as SS will shift freely between 1st and 2nd but then hold in all other gears.

SS is a bit awkward for me because I learned on and drove a stick for a long time so I tend to let off the gas out of habit when shifting lol.

tartilc

Yup, I think that's how it works as I don't remember it ever kicking down when I used it. My daily before I got the TL was a stickshift so I get what you mean haha, the shifter also moves in the opposite direction.