GotZoom76

Hey all,

My son owns a 2000 Civic DX with 156k on it. Bone stock..

The issue started with misfires on cylinders 3 and 4, flashing cel, burning fuel smell from cat and very sluggish at anything over 40mph or going up a hill.

We replaced the plugs, wires, Dizzy with everything inside replaced (can’t remember what it’s called). Also changed oil, air filter and all four fuel injectors.

Car ran great upon teat drive yesterday. Today however the idle is extremely rough while in drive and at a stop sign or stoplight. Under load it evens out and is fine. CEL came on and I pulled the codes which were P0170, P0172 and P0175. Researched the codes and see many different things, many of which we have already replaced.

I do notice a sputtering air sound coming from outside the car and around the car/exhaust manifold. I also stuck my hand behind the tail pipe and it doesn’t seem like a lot of exhaust air coming out. Upon driving home after resetting the codes we also smelled burnt exhaust inside the car. It was strong but it was there. It was not a rotten egg smell but again more like burnt exhaust.

Maybe a cracked or damage exhaust manifold sucking in air?

Should I do the ecm relearn? I didn’t after all of the above work.

Possible MAF or MAP?

Just trying to get some more ideas or suggestions as he is tired of putting money into it.

Sorry for the long long post but thanks in advance.

Cheers!

muellersfan

Compression test the cylinders.

California98Civ

The ecu is adding fuel to relieve an actual or perceived lean condition, but the codes mean it has reached its limit in terms of fuel trim. Some possible causes for an actual or perceived lean condition: vacuum leak, exhaust manifold crack ahead of the primary O2, exhaust valve lash...

muellersfan

I absolutely disagree. For example, an exhaust manifold crack ahead of the primary O2 would definitely throw P0171 (lean) rather than P0172 (rich).

And a vacuum leak would produce a high idle speed. OP does your engine exhibit this problem?

And how would either of these issues cause misfires primarily in cylinders 3 and 4?

Sounds like two dead cylinders.

Compression testing the cylinders is the place to start. Then go from there.

GotZoom76

The car does not have a high idle and actually seems a little low when slowing down and coming to a stop. This followed by the shaking. Drove the car twice today with no issues, even when stopped. Once in park or neutral the car idles just fine when the above issues are happening.

I believe the misfires on 3 and 4 were in fact due to the injectors. They were pretty nasty. I have not thrown any misfire codes since I replaced those. I did the screw driver test and they seemed much different than 1 and 2. I did replace all 4.

I again point out the, imo, the amount of exhaust pressure coming out of the tail pipe is weak and I do hear what sounds like air flutter/sputtering from under the car and near the exhaust manifold/cat. I am not able to get the car on a lift atm and can only put it so high in jack stands.

From my understanding, the code previously reported could be caused by a cracked manifold, dead or dying cat, or the o2 sensors. If I am wrong please let me know. I’m all about knowledge and learning.

Thanks again!

muellersfan

Are you referring to P0172 here^?

Is the engine running now?

Are any CEL codes currently thrown?

GotZoom76

Correct..

Also p0170 maybe? I thought I read it’s a transmission sensor related to what the o2 sensors is sending in terms of communication.

muellersfan

P0170 indicates an unspecified fuel system problem. P0172 specifies the fuel system problem - running rich.

A cracked manifold would never throw P0172. See diagram I posted.

Are any CEL codes currently thrown?

What are the current performance issues?

GotZoom76

No current codes since I reset two days ago. Also no current performance issues. Basically trying to see if I can get it to throw the same codes again. I also plan on doing a compression test this weekend.

GotZoom76

After I replaced the injectors we drove it for about 30-40 minutes. Had the erratic idle in drive and at a stoplight one time and then it went away. It did not throw the cel though.

Next day, drove it for about 15 minutes and then parked for about an hour. Drove it to work 3 miles away and the shaking returned at a stoplight and in drive. This time it threw cel with the codes mentioned.

Pulled the codes and reset them. Drove the car today to work and back with no issues.

California98Civ

I'm not disagreeing with you. The OP is asking for testing ideas. He says he got a p0175 and that he can hear some air sputtering around the manifold and other areas... seems like a possible vacuum leak. There can be more than one problem, no?

muellersfan

These Civics don't have a code P0175. See chart below. P0175 is most surely a typo by the OP.

California98Civ

Great reminder to use only my FSM for reference. Thx. Seems there is no p0170, either. I still wonder about the hissing, air leaking noise he describes. You don't think there is any chance a vacuum leak is contributing to his chaos?

GotZoom76

I took pics of all the codes I received. See attached.

California98Civ

Maybe a really clogged CAT could obstruct exhaust that badly, but the secondary O2 sensor should throw a CEL for poor CAT efficiency, wouldn't it? I think checking valve lash is still a possibility (ONE possibility, not THE ONLY possibility). Maybe the exhaust valves are hardly opening.

muellersfan

Code readers are designed to pull trouble codes from many different car makes and models. This is great, but an accompanying problem is that code readers also commonly spit out a lot of red herrings (junk information).

The OP's last post reveals four current CEL codes -- P0172, P0170, P0175, P0705. Three of the latter codes are completely redundant (P0172, P0170, and P0175) because they report the same fuel trim fault.

Only one of the codes is used by 96-00 Honda Civic ECU -- P0172. Consequently, you will find detailed troubleshooting for this code in the 96-00 Honda Civic service manual.

P0705 suggests an automatic transmission sensor fault. To identify this potential fault, the OP would need to short the service connector and watch the D4 light in the cluster blink the transmission code (numbers in parentheses in table below).

The OP should also clear all codes from the ECU and see whether the codes repeat before troubleshooting.

Does the engine still make the hissing noise? Or is this issue gone now?

What engine performance issues, if any, are currently evident?

GotZoom76

Codes were reset a couple of days ago and have not come back as of yet. Performance as of now is where it should be.
The air sputtering is still present, under car, middle and appears to be near the lower part of cat.

Regarding P0175.. Since he has owned the car it has never displayed the D4 light on the dash and as a matter of fact the transmission goes right into D3 from day neutral and is then bumped up one into D4.

3 or 4 days ago was the first time P0175 was indicated. This was going to be my next area of troubleshooting once I could get the rough idle figured out. My kid thinks the rough idle when stopped is only after the car is really warmed up.

muellersfan

P0175 = P0172

...so I think here^ you mean P0705 not P0175. Jumping the service connector is a simple process.

The hissing is not a vacuum leak if the idle speed is normal rather than high or hunting. Post a video with sound.

The location of the hissing suggests an exhaust leak in exhaust pipe A.

A mildly rough idle might just be a dirty IACV that needs cleaning.

GotZoom76

I will definitely try to get video.

We we just had the exhaust pipe from the cat to muffler replaced last week. It did have a good size hole and was really loud.

Come to think of it, the codes mentioned did not present themselves until after this was completed. Only misfire codes previous to this and those have since went away. When it was throwing the misfire codes, acceleration was horrible and bogging up a hill or anything over 40 and also had a flashing cel that would then go solid. This is no longer happening since the fuel injectors were replaced.

The low rough idle when in drive and stopped has always been there since owning the car but again it is hit and miss.

muellersfan

Maybe the shop did not replace the exhaust pipe gaskets?

You would probably eliminate any roughness in the idle speed by cleaning the IACV with WD40 and brake cleaner followed by adjusting the idle speed to spec (see service manual for proper procedure).

GotZoom76

I can’t imagine they wouldn’t have replaced the gaskets but hey who knows. The receipt shows the pipe, flange and gasket. When I looked under the car after we picked up it all looked new.

Will definitely try your recommendations on the IAVC.

Thanks!

muellersfan

You may be able to pinpoint the source of the hissing by crawling under the car with the engine idling. Good luck!