orbanp

Hello Everyone,

Car is a '97 Civic LX, Canadian model, 5MT, with 132kMiles on it.
There is a crack at the upper ox-sensor, running towards the head. Not sure how long it goes, have not taken off the heat-shield yet.
No exhaust noise is coming from the crack.

The car started throwing error codes, P0170, P0171, lean condition, and fuel trim (control system is out of its compensation range).

Upstream ox sensor has about 65Kmiles on it.
Fuel pressure is fine, changing with the manifold vacuum within the range given in the manual.
Could not find any intake manifold leaks, there is probably none, based on the intake pressure range, as seen from the fuel pressure.

I am guessing that the reason for the lean condition could be the manifold crack.
On this car the exhaust manifold also does include the catalytic converter.

What are the options?
Does the crack open up eventually even more? Looks like a crack at the upper ox-sensor is "quite common" on these cars.

- I have seen one guy filling in the crack with some high temp goop, he reported back in a couple of days that it still lasted, and he passed the emission test. No long term reporting.

- There are a number of aftermarket manifold/converter assemblies available, are those any good, any of them preferable?

- I understand here (in Canada) scrapyards recycle the converters, though have not checked if used manifold/converters are available.

- Reading the internet, in the US there was an extended emission warranty on these cars for 150kMiles, the EPA forced Honda to do that.
Was/is there similar warranty on Canadian models? - I could not find any trace of it. Honda probably would not admit to it.

- Any other option?

Thanks, Peter

Poopies

iTrader: (4)

Replacing the manifold AND the cat sucks. I have heard bad things about aftermarket cats.. maybe try to find a used one at a scrapyard or something? I would probably try the goop before buying a new OEM one... what do you have to lose?

orbanp

Well, the crack is "functional", there is exhaust leak there!
Checked it with a flame, it was blown out when the candle lighter was moved close to the crack.
So that crack could indeed be the source of the lean condition error code.

Checked with the dealer, emission warranty was 5 years or 100,000km on that car.
The bad news is that a new Honda exhaust manifold/converter from the dealer is about C$940.00, plus about C$200.00 for heat-shields and gaskets. Expensive!

Peter

Poopies

iTrader: (4)

Definitely expensive. They should be able to reuse that heat shield too...

Wankenstein

Ebay, car-parts.com or local salvage yard a used manifold/cat and replace it yourself. Should be able to swap it in less than two hours. Soak the bolts in PB overnight and if that doesn't work then torch them or cut them off.

orbanp

Hello Everyone,

Just an update on the error codes: the car stopped throwing the error codes!
Has done nothing to the car, just deleted the codes every time when they came up.

The other part of the story is that the error codes came up first time after a long highway drive when my son filled up the car at a noname gas station. That gas probably contained ethanol.
We always use Shell gas.
My understanding is that Shell does not use ethanol in its regular grade gas, while other stations may use up to 10% or 15% ethanol.

The error codes never came back while driving in town, they came back only when driving on the highway.

Now it looks like that after a number of fill ups with ethanol free gas the error codes do not come back, not even after a highway drive.

Is there any credence to this theory?

Reading on the net, ethanol could confuse an ox-sensor, and high level ethanol (E85) could even "ruin" and ox-sensor.
Any comment on that?

Peter

ezone

10-15% Ethanol fuel alone does not cause lean codes. I'm in the rust and corn belt, it's all but impossible to get gas without Ethanol here. If 15% causes a code then there was already an underlying slight lean issue that wasn't bad enough to code by itself.


A full tank of E85 sure will cause lean codes.
A partial tank of E85 probably would. It depends on how much good gas was left vs how much E85 was dumped in.

Back just a few short years ago when gas was $3-4+ per gallon, I saw this happen A LOT because people would push the button for the cheapest price on the pump without looking at what they were going to get LOL

Depending on how empty you ran the tank prior to refilling with good gas, it could take quite a while to get E85 diluted enough with good gas to clear up the code issues.

If the gas station got a full load or partial tanker load of fuel dumped in a wrong underground tank, or just contaminated fuel, that also could explain how this occurred.

Tim1959

I had this same problem on my '99 Civic LX. I think this is a pattern failure on the 6 Gen Civics. The exhaust manifolds start cracking and leaking a few weeks after the warranty expires. Planned obsolescence? :-) My car would have eventually failed smog testing in my state (throwing codes, MIL light on). I tried patching with "high temp" exhaust system paste. This only lasted a few days. The crack continued to spread, the code came back. The price for an OEM manifold/CAT was ridiculous! (like $1000). I found an aftermarket (Dorman) manifold/CAT on Amazon.com for about $170 plus shipping. I installed the Dorman manifold/CAT on 3/17/16. I've driven the car about 7,000 miles. No problem so far. The car passed smog testing. The old manifold/CAT has scrap value. Do NOT throw in the trash! A local scrap yard paid me $20 for mine... :-)

Wankenstein

Could pull a manifold and bolt on cat from a salvage yard EX model and swap it.

Tim1959

I think the only problem with this is that this is a "pattern failure" with 6th Gen Civics. Therefore, any used manifold/CATs you buy will have a limited lifespan. Plus, the aftermarket manifold/CATs are fairly cheap ($170).

Colin42

the ex model has a "header" and then a downstream cat, as opposed to the manifold cat, the 7th gen has the same set up and they crack too

Tim1959

So this may be a design flaw from Honda. This is the only car I have ever seen that has the exhaust manifold & cat converter combined. And I've seen MANY cars, since 1974! :-) The aftermarket manifold/CAT (Dorman) I installed has held up fine for the past 7,000 miles (since March). I guess only time will tell.

Colin42

Meh, it's a relatively minor flaw. You need to think in terms of physics; that's big lump of metal that's supported by a relatively thin casting So for it to last over ten years and thousands of heat cycles is pretty good. I've seen the cracks get welded up and they hold up for a long time after that.

Tim1959

The thing is, the vast majority of cars have the exhaust manifold & cat converter separate and they do not fail as frequently. When they do fail, they can be replaced separately. The combined exhaust manifold-cat converter for my car costs over $1,000! I do not see an advantage to combine the exhaust manifold & cat converter. MOST auto makers do NOT do this. (expensive design flaw) Honda makes GREAT vehicles! No automaker can be flawless all the time.

ezone

The bumper to bumper warranty on a 99 car would have expired around 2002 ish....are you saying yours has been broken for the last 14 years?

The design concept is not new at all.

In fact, in the interest of meeting modern emissions standards the majority of manufacturers these days have the cat located as close to the engine as the engineers can reasonably get it.

A cat may be found more or less bolted directly to the cylinder head now.

Tim1959

Yes, this is true, but these same engineers were smart enough to beef up the exhaust manifold so that it didn't start cracking and leaking causing DTCs to get set.

Colin42

It's hard to design things for the long term when you can't predict the future. Honda has improved their design for the newer cars. My old escape had the cats right after the manifolds as well because that way the cat heats up quicker and the vehicle doesn't pollute as much.

Tim1959

Okay, I understand why they put the cat close to the cyl head. The design flaw must have been resolved (on these particular cars) because I never hear of this kind of expensive failure on other cars (Honda & otherwise) over the past 15 years.

ezone

Whenever you bolt a long cast iron exhaust manifold to an aluminum head and do not allow for differing expansion rates, there's bound to be problems eventually.
Honda changed the heads to incorporate the manifold within the aluminum head casting. The exhaust/cat connection is now a much smaller port and the cat bolts directly to it, with just enough room for an AF sensor on top.






Every manufacturer has a fair share of problems.... Honda is certainly not immune....but take a look around:

Ford, 3 valve spark plug problems, 2.3L engines drinking oil, newer Diesel problems,
Chrysler Hemi broken manifold studs, other engines burning valves, breaking valve springs, dropping valve seats......Any chrysler engine that ends in .7 develops sludge problems.....Ball joints made of cheese, transmissions every 30k, water pumps, expensive modules....
GM LS lifters and camshafts...other engines eating timing chains,


There's a Chrysler dealer next door to where I work, I get to hear their tales of woe more often than the other brands. I'm sure the other brands have tons of their own horror stories too.

Wankenstein

Late 90's to mid 2000's Cadillac head gasket issues. Subaru head gasket issues. Even certain engines from Toyota had issues with head bolts stripping.. not to mention the sh!tload of recalls they've had in the past decade.

Another thing that sucks is manual transmissions are almost obsolete in new cars:

Remember when there were manual transmissions? Remember?:

ezone

Neon/Stratus/Breeze/Mitsubishi (Mopar 2.0/2.4) head gasket fiasco? Mopar evaporator cores?
Honda is bringing some of them back (Civic, Fit, Accord, ....?), but it sure seems like my dealer receives very few to sell....maybe because nobody buys them.

Tim1959

For many YEARS I insisted on owning & using manual transmissions. As I aged (I just turned 57), convenience & versatility outweighed performance, and I now use automatic trannys exclusively. :-)

Tim1959

Integrating the exhaust manifold into the cyl head seems like an effective solution to the problem of cracking exh manifolds. I forgot about this. I only heard about this recently. I guess I need to update my knowledge of modern automobile technology. :-)