bimmernut

I just got a 92 VX, that has a badly rusted exhaust manifold, cat and the o2 sensor seems like it has been in there forever, (code 48 and 21) so I was thinking of going with headers. If I do, does the o2 get put in before the cat or after, the kits have 2 bungs and I have one sensor. And can anyone recommend any brands or know of any to avoid. Thank you

mikekh10a

iTrader: (2)

OBD1 needs only 1 o2 sensor, which goes before the cat.

bimmernut

thank you. will it make any difference on mpg?

mikekh10a

iTrader: (2)

will what have any difference on MPG?
i know the absence of an o2 sensor will throw a CEL, and will stump your MPG quite a bit.

beecee18

not to mention OP's car has a wideband sensor instead of a narowband sensor making it much more expensive, which helps contribute towards its record of great fuel economy. Note its ultralightweight enkei wheels....
These were implemented for reduction of drivetrain mass, which was also another design for greater fuel economy.
IMO this would be one of the worst hondas/less benifiting setup for an aftermarket exhaust. The model itself is awesome for two setups

1 swap/race car due to its lightweight.
2 keep it stock and benifit from its awesome fuel economy.

You would be better off buying a known good used manifold for replacement, and possibly replacing the sensor if needed.
This all depends on your plans for the vehicle.

bimmernut

I use the car to commute 70 miles one way to work, mostly on freeway, so I guess the stock system is best. I've got the 48 code on cel, so I need an o2 sensor. There is a 5 wire ntk sensor on ebay for $100. Are these ok to use or should I bite the bullet and go for the oem?

beecee18

I personally would have no worries trusting the ntk, which if im correct is a ngk product. It should have no problem performing like the original, but probably better being new, this alone should help with the mileage.
If you have any local wrecking yards around I would definitly check into finding a good used manifold.
Im also not sure if the VX's manifold is special to that model only, but someone on here would have that answer. As if it were the same as any other civic model, it could easily be had.
Also im not sure of what the code 48 is exactly until I check. But it might not be the sensor. Its possibly the sensor reading the wrong o2 level due to the introduction of air through the failed manifold. The sensor sees this extra air, and makes compensations to add more fuel to level out the fuel mixture. This is where you consume more gas.
I would honestly start with replacing the manifold, resetting the ecu, then troubleshooting further if the engine light returns.

bimmernut

I hit 2 junkyards today, looked at 27 civics and none had the same manifold. Code 48 is the o2, and code 21 is the vtech control solenoid. Honda dealer parts guy said the oil pressure switch which is mounted into the control solenoid could be the cause of code 21, but at $70 I prefer not to take a chance that that is giving the cel. My manifold isn't cracked, but I snapped off one of the exhaust shield bolts, and I can't budge the o2 sensor. I've been spraying it daily with penetrating oil, pb blaster but no luck. My neighbor says he can hit it with the torch and free it. My cat looks pretty rusty also on the connecting points so I was thinking of replacing cat and manifold. However, the manifold is a little pricey, $210, and the honda cat is $450. Dorman has an ex man for under $100 but is oem the way to go to get the best mpg?

bimmernut

Does anyone have a good used exhaust manifold and/or catalytic converter for a 92 Civic VX? Thank you

cvcrcr99

The exhaust manifold has a cat converter built into it from what I remember when I had a VX hatch. Just like the non vtec 96-00 manifolds. You should try posting in the WTB section in the marketplace.

bimmernut

I tried, but I just recently joined the ranks and still have to wait another week or so.

beecee18

Is the manifold/cat leaking?

I was under the assumption that it was cracked or leaky.
If it is not I really dont see a need to replace that unless the rusty look is eating at you. Also if it was not, the best next thing to do is troubleshoot the problems that are known, which would be the replacement of the O2 sensor.
And troubleshooting the vtec solenoid.

If you know that the exhaust manifold was leaking or was cracked then that would warrant a replacement.

Also keep soaking stubborn rusty bolts, torch would be last ditch effort.
And try to use top quality tools for the removal of the stubborn O2, I personaly would use a extralong snap-on open end wrench to tackle that job after days of soaking. Crapsman and worse wrenchs dont accomodate your circumastances. You need the extra leverage, and quality of the tool to not round off the hex on the sensor.

First thing is first is the wiring from the o2 sensor needs to be inspected for faults/breaks in the wiring, same for the vtec solenoid/pressure switch, as OBD1 hondas are notorious for illuminting the engine light only if there was a broken/failed part, or an open circuit which would indicate break in wire ect.
Most of the time you will not net the light even with the broken part.

bimmernut

the manifold wasn't leaking, I just snapped off one of the heat shield bolts so I drilled and tapped it. I guess I'll order the ntk sensor, and keep soaking the present one until it arrives, then go for the removal. The cat's heat shield is really eaten up with rust, I think the car grew up in Illinois, and the place I bought the car from replaced the exhaust from the downpipe on back, so I think the cat might need replacing. If so, do you think oem is the way to go or aftermarket. Again, thanks so much for all the info. Car has 145,000 mi. and the place I got it from also welded on new lower quarter panels due to rust.

mikekh10a

iTrader: (2)

i never had a problem with cats from magnaflow

hyperman92

what engine does it have in it? I have some edelbrock headers for a d16a6/z6 laying around that I might be willing to part with if the o2 sensor isn't the issue.


Posted from Honda-tech.com App for Android

bimmernut

It's got the D15Z1 engine so I'm gonna stay with a stock set-up. Thanks, tho.

eingman

if ur not really going for performance ebay is the way cheap and ok. replacing the o2 sensore sould increase gas milage

beecee18

Wow rust is not a big issue out here in cali,
145k is not that bad, the heat sheilds are just that, heat sheilds,
So if this vehicle is just used primarly for commuting and you are looking to get it up to factory correct operating condition, and save money doing that.
I would recomend one part at a time.
If it were me I would

1. check continuity of 5wire o2 from sensor to ecm
2. check continuity of vtec spool valve assy. to ecm

These first two steps will just rule out that we are not getting these faults from breaks in the wiring, loose harnesses, ect.

3. replace o2 if step 1 does not rid of the o2 code
4. replace vtec spool valve assy. if step 2 does not rid of the code21

Of course resetting the ECU between all of these steps.
And then I would troubleshoot/replace other parts further, not necesarly the cat or manifold either, just one step at a time.

If you do not have an online copy of the service manual that pertains to your application, then me or someone here can email you, or host images of the exerpts needed to troubleshoot/repair process for each of the two codes you have.
They are called flow charts. These flow charts are going to have you test correctly for each fault so we are not just throwing parts at your car, and badgering your wallet.

bimmernut

Oh man, that is just the info I needed. I'll do the continuity checks and see what happens. It may be a few days before I get to do it, but I'll post results.
Thanks so much.

beecee18

Im gonna try and get you the flow charts before then,
it will instruct you exactly what pin at the ecu and sensors to test for continuity.
Its not hard just time consuming.

beecee18

http://www.redpepperracing.com/techn...Civic-FSM/120/

11 (38)
11 (39)
11 (40) these are for the O2 sensor (Lambda air fuel) for code 48
start with this first as the vtec solenoid is not as important for your circumstances.

canadaek

also its header !!! there is only one unless your rocking a j swap

hyperman92

wow grammar correction, really?!


Posted from Honda-tech.com App for Android

EsotericImage

iTrader: (8)

Not so much a grammar correction, but a point in the right direction.

Just like when kids call it VTECH

its better to correct someone who's a noob so they dont sound like a noob when trying to talk shop. Headers [plural] means 2, and theres only 1 on a 4 cyl.

bimmernut

as long as we're correcting grammar, it is "you're", not "your"