juror

Title says it all. I've been making the same 25 mile (one-way) commute for the last 2 years, and have become accustomed to getting a strong 35 mpg in the summer, and a little worse in the winter. Suddenly, I'm at a weak 30 as of a couple of tanks ago. Our mileage over the Thanksgiving holiday was also pretty weak for light traffic highway driving, say 33 instead of the usual 37-38.

Earlier in the fall (October?) the MIL came on with a P0139. It went out before I got a chance to order a new one. It came on again and went back off the next day a week later. The MIL is currently off, but this suggests that the sensor might be marginal?

Given that a downstream O2 sensor is $28 on rockauto.com for Denso 234-4220 (which is the OEM part, as near as I can tell?), should I just throw one at the car and see if things perk back up? Or is there something else I should check first?

Unrelatedly, I need new wiper blades, so the shipping from rockauto is essentially free if I compare the cost of buying wiper blades locally, so we can ignore that cost. Actually, for what wiper blades go for retail, I'm probably down to about $10 or $15 for the O2 sensor...

Prior, possibly relevant thread about the same car:
https://www.civicforums.com/forums/3...placement.html

TL;DR: The downstream cat was replaced in January 2018, with the original downstream O2 sensor retained. It failed a month or two later and I had them replace the downstream O2 sensor (I thought maybe there was another leak based on the sound, they determined it was the O2 sensor. I had them fix it because they're good guys and I usually only bring them problems I can't fix).

Thanks!

juror

Oh, and for the amusement of anybody who read through the end of the linked thread, I had to re-zip-tie the CVS solenoid a couple months ago. Whilst wrangling the canister back on, I stupidly let go of the socket wrench with both hands to wiggle the canister just so. The socket wrench slipped off of the rusty bolt, and landed on my face. Much swearing ensued; I was not happy, to put it mildly.

GolNat

iTrader: (7)

A dirty or bad O2 sensor can cause poor gas mileage.

Check tire pressure.

Slumpertcivic

juror

Thanks for the suggestions. I'll follow up once I get a chance to check those things.

These are unreasonably fun for reasons I can't put a finger on. Some years ago one showed up in our office and my coworker (55) and I (25) spent a whole afternoon taking the temperature of random things around the office.

Slumpertcivic

Colin42

Because you didn't want to do work?
Thermal image cams are even more fun

sdaidoji

iTrader: (1)

they sure are.

My FLIR ONE

sdaidoji

iTrader: (1)

of course the best ones are the farting ones.

juror

Wow. This thread has taken an interesting turn. Bringing it back to cars:

Tire pressures are 30-31 on all four tires. A hair low, but probably not low enough to bring things this far down.

I just changed the oil. While I had the car on ramps (I know, I know) I took the opportunity to pull the downstream O2 sensor and take a look at it. It looks "fine" to me, or at least it doesn't look like any of the pictures here. The text on the sensor reads

DENSO
42070
09U07

That doesn't correspond to anything I recognize as a Denso part number, but maybe somebody more savvy can tell me what it is and if I ought to just order up Denso 234-4220 from RockAuto with the aforementioned wiper blades.

My wife is going to borrow the IR thermometer from her office tomorrow, and hopefully I'll be able to get some info out of that.

Thanks everybody who has weighed in so far!

GolNat

iTrader: (7)

I would check Denso's website for the part number just to confirm.

That part number from RA didn't match my quick search on Denso's website but I used an 03 Civic you may have a different year.

juror

We have an '05, and when I searched, all the part numbers for the O2 sensor are of the form 234-4xxx (the LAF sensors are 234-9xxx). Like I said, it doesn't even look like a part number. I can't find any parts on RA made by Denso with that part number either :-(

juror

Developments:

Back in December, my wife borrowed a FLIR from work. I checked wheels before and after my commute and had readings within 10 degrees (F) of each other front and back. But read on.

Somewhat later back in December, the MIL came on again with a P0139. I ordered up a new O2 sensor. After getting back from the holidays, I put it on. 2 tanks of gas in, no improvement.

Today, however, we had a break-through. I got off the highway on my commute this morning and smelled hot brakes. It dissipated by the time I parked so I made a mental note. Tonight, on my way home, same thing. I pulled over, sniffed each of the wheels in turn, and confirmed that the front left was hot. Qualitatively, I couldn't leave my hand on the wheel on the left side, but could on the right. I think we have our culprit. Will confirm once I replace the caliper.

So, credit to Slumpertcivic. He nailed it back in December: https://www.civicforums.com/forums/3...ml#post4755367

Dunno why we didn't see it with the FLIR, either it wasn't dragging bad enough to stay hot for 10-15 minutes after I got off the highway, or it was an intermittent problem at the time.

Also, to our considerable disappointment, neither my wife nor I was able to conjure a fart for the FLIR while we had it :-(

juror

Incidentally: should I replace both calipers while I'm at it?

sdaidoji

iTrader: (1)

i would first pull out the slider pins and re-lube them. Don't forget to check for the bearings.

Sad to hear you could not get a reading of the fart

Colin42

Personally I would, the other will probably go in a month

juror

Dumb question: How would I know if it's a wheel bearing issue rather than a brake issue? Both times I've had a bearing issue (same one twice on my 2006 Impreza (bum replacement part, garaged re-replaced it under warranty)) the symptom has been kind of a rumbling noise, not heat.

GolNat

iTrader: (7)

Wheel bearing is possible. You can check it but jacking up the suspect wheel and giving it a spin and a twist. When spun by hand it should glide smooth and not have much noise (the brake might make a noise). Also grab the wheel at 3 and 9 and twist (front to back) and see if there is any play.

You will have to inspect the slide pins and pads to see if the caliper was dragging. If you smelled brakes which do have a smell to them then the caliper is probably the issue.

juror

Got it, thanks. I've ordered up calipers because I'm reasonably confident that the state inspection last week probably would have caught the wheel bearing (they caught a bad tie rod end on the other side). Since the state of MA started putting cameras in the inspection bays, they're actually pretty thorough. Most garages used to take 5 minutes, now they take 30.

I'm also going to add that the calipers looked pretty ragged (New England winters...) last summer when I did a brake job. If I could get this one back, it would probably be very temporary. And since I'm doing this in my driveway, getting the car in the air is a significant part of the hassle of doing any job on it. I don't want to have to put it up twice, especially not in January. For $110 on rockauto, I'm just going to replace the parts.

I'm also trying to avoid this one stretching out past the long weekend; if I pull the trigger on the parts this morning, I should have them by the weekend.

I'll report back once the job is done on the state of the existing caliper, and on the mileage once I run a tank or two of gas through it.

sdaidoji

iTrader: (1)

ok
good luck and let us know how it goes

NDNV

I've replaced 3 out of 4 calipers so far at 200K kms (125K miles). Diagnosis of one of the bad calipers was when pressure washer sprayed on wheel and it steamed badly. Others were by mechanic's assessment.

juror

Update: I put the new calipers on last night. It was a 2-hour, 2-bandaid job, and it was 26F out when I had the wheels on the ground and the tools put away. None of the bolts were seized - Hooray!

Both calipers looked like hell; the inside of the pistons were full of flakes of rust. The left brakes were reeking again when I got home. The pads on the left side are a little worse than the ones on the right, but both sides should be good for another few months at least.

The car is much happier now. I'm only 40 miles into a new tank of gas, so I can't quantify this, but I can say that the vibration in the steering wheel on the highway is gone. Yup, the left was dragging bad enough to warp the rotor. Fortunately, the rotor goes back to true once it cools.

Oh yeah, and the MIL came back on this evening. Haven't had a chance to scan it yet. Hoping it's the P1457 that seems to come and go with some regularity, not the downstream O2 sensor.