2003 Honda CR-V exhaust fumes in cabin

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No trouble codes. Less odor with vents on recirculation. The fumes are present even while driving, so I lean toward the leak being in the engine area or forward part of the exhaust. There's no evidence of a rich burn, though, per my wife, the gas mileage has diminished. Otherwise, the car runs great (gutsy little engine). Visual inspection was negative both hot and cold, running or off. No black marks or obvious leaks. The engine has no obvious leaks, off or running. To my knowledge, the car doesn't have an EGR system. This was a big surprise. I thought it might be a slam dunk: a leaky EGR pipe. Apparently some Hondas had an EGR plate with a gasket and passages which commonly plugged. I thought there may be a leak at this gasket, but I don't see this setup on the car (2.4L). Pressurized the cold exhaust system with shop vac, sprayed soap. Found small leak at rear O2 sensor (Bosch universal replaced by me last year). Pulled it out, cleaned up the seat, sealed up nicely. The only area I couldn't inspect well was the manifold because it is blocked by heat shields. I also couldn't really see on top of the system, but i may get out the inspection mirror and check. I suspected the flex joint between the manifold and converter pipe, but here was no bubbling. I did spray the entire system, at least all that i could access. No leaks. Took it to a very reputable shop, they also found no leaks, but suspect it is the converter. Though I don't completely discount the possibility, it doesn't make sense that a bad converter will magically push exhaust into the cabin without an obvious leak. I voiced my concern with the shop, and they honestly agreed that the signs/symptoms don't align well. And they reiterated that they did not find any leaks. I can replace the cat and O2 sensors for around $500, but I'm not yet convinced it is the issue. I suppose I could troubleshoot the proximal sensor, but that still doesn't explain what appears to be an exhaust leak...and there is no code, and the car runs fine... I may run some more tests. It could be that the leak doesn't occur until the system is warm. I may warm it up and try spraying soap around, or block the pipe, or add seafoam and look for smoke (a nasty option). I'm wondering if I'm missing an emissions component. I haven't determined if the odor occurs only while driving (throttle open) or at all times. Maybe there is a not-obvious emissions component that opens with the throttle (PCV seems fine, opens with rev, but i could replace it--not easy, by the way). May take it to the Honda dealer: they know their cars, and the common issues. I'm going to keep looking, but wonder if you folks have any additional suggestions...? Many thanks, Bob<----need some clues!
 
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It sounds like you checked the exhaust system pretty well. Could it be from the rear hatch seal? I thought that hatchbacks created some sort of air pressure setup that could pull exhaust into the cabin. Maybe start the engine from cold while you feel around with your hand at the manifold and joints. You could also smoke test the exhaust with a smoke machine. Maybe the smell is not exhaust but something else like oil leaking onto something hot, or a brake getting hot.
 

Loogie

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I did check for obvious engine leaks, but the one area i can't visualize well is the exhaust manifold. I may try to get the heat shield off. The odor smells like exhaust, rather than burning oil/coolant/etc (plus the car isn't using/losing any fluids). But, it is worth checking out. I would be positively giddy if it were the valve cover gasket. I need to lay eyes on that manifold. Bob
 
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Exhaust smell in the cabin is serious business. I would suggest going to a shop that has a fogging machine to check for these kinds of leaks. Also, I remember there was a poster here, I haven't seen him post in a long time, that had a CRV, I think 06 or so, maybe 08, but he said he needed to replace the catalytic converter donut gasket pretty much on regular basis. It would go every few years. Check that/
 
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You sure it's coming from your car, or is really exhaust fumes? Put a CO alarm in the cabin, for one. CO doesn't have a smell... Anyway, flex pipes are common leak areas, as are cracked manifolds and missing manfold bolts/blown gaskets.
 
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JOD

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This may be a bit of a Hail Mary, but... I'd check the spark plugs. After doing a valve adjustment on a similar age CRV, I had a spark plug loosen up after about 5K--and it was causing an annoying fuel smell into the cabin. Plugs were torqued correctly, but I remember at the time thinking "boy, the torque spec if really low?". May be work a quick check. BTW, if you've never adjusted the valves, it's probably a good idea if you have 100K or more on it. I did it at 60K and all of the exhaust valves were too tight.
 

Loogie

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You guys are awesome, thanks! The valves were adjusted about a year ago. -I replaced the plugs a bit over a year ago, but I will recheck torque. -I did place a CO alarm in the car. Kept the vents on recirc no levels detected. I don't recall if I tried with the vents set to outside air. -I'm 99% sure that it is an exhaust smell (been working on cars for 30 years), but the senses can be fooled. I like the thought process:. A minor exhaust leak isn't necessarily an issue if the gasses don't enter the cabin. So: how are the gasses entering the cabin? I was focused on the exhaust, but neglected the cabin seal as part of the equation. So, there are at least 3 possibilities: -sealed exhaust and a malfunction of the cabin seal -leaky exhaust and a malfunction of cabin seal -leaky exhaust and proper cabin seal (exhaust leak is in an area which is prone to being sucked into the cabin air intake). Via cursory exam, the door, window and engine compartment seals are ok, but I will carefully assess them. I had no idea that there is an air vent in the rear quarter! I would guess it is a one-way cabin exhaust vent. Will check that out. Bob
 
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I have an 04 CR-V, and I just replaced the whole exhaust system about 6 months ago. Except the muffler, because it wasn't leaking at the time. But it's leaking now... smirk2 There's nothing really special about the manifold. It uses spring bolts and a thick donut gasket to connect to the converter pipe. There is no flex joint. There's no EGR or anything else bolted to it. My converter was rusted out and the shell was starting to fall apart. A previous owner tried to patch it up by wrapping sheet metal around it, securing it with a hose clamp, and smearing that muffler putty stuff all over it to try and make it airtight...needless to say, that didn't last long. It started making noise a few months into owning it. I recall smelling exhaust fumes inside around the same time it started making noise. I haven't smelled anything since replacing the exhaust.
 
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I once had a Sonata that had a bad "exhaust" smell in the cabin. Turned out to the a cross-threaded oil fill cap that didn't seal. The odor was coming right in the vents. If the smell lessens when on recirc, I'd focus on the engine bay area. Seems to me if the smell is entering the cabin via the exhaust under the car or in the rear, it would get worse with recirc.
 

Loogie

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I don't know how to edit my initial post, but I solved the problem! I checked everything mentioned in the thread, and all was fine. The possibility of a dysfunctional cabin exhaust door was an interesting theory. It is buried in the driver's quarter panel, and isn't easily accessed. When I turned on the fan, you can hear and feel air rushing out below the lower aft section of the panel. Given the challenging access, I wasn't sure how to check it. The problem solved itself when I closed the door and heard the vent pop open and closed. I spoke with a Honda expert, and he thought it was the flex gasket between the cat and manifold. He was perplexed as to how the exhaust was entering the cabin, but was confident that the gasket was the issue, as it is apparently a common one. He stated that if there is minimal gap between the flanges, the gasket was toast. Mine had only a little gap. I ordered the parts for about $33 shipped. I did order new springs despite their alleged longevity. Replacement wasn't too bad, and sure enough, the gasket was intact but clearly trashed. I could see a dark area on the upper flange which was clearly a sign of leakage. I also solved the mystery of how the exhaust was entering the cabin. I happened to notice a rubber hose, which I had not noticed before, exiting near the offending exhaust joint. A few seconds later it hit me: it was the A/C drain. I theorized that as air flows over the tube entrence located below the evaporator coils, it creates a low pressure zone, thus sucking in noxious exhaust from under the car. I tested my theory by running the cabin blower and blowing out a match: the tube sucked the smoke right in! Interestingly, it occurred on both recirculation and on the outside air setting, but the suction seemed less powerful on recirculation. I'll try to attach a picture of the tube. [Linked Image] [Linked Image] Bob
 
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Some vehicles actually have a flap over the end of the AC drain just for that reason. On every vehicle that I have that I can, I extend the drain hose away from the exhaust.
 

Loogie

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I've been wrenching on cars for 33 years, and was a master mechanic many years ago, but I'm still learning. Bob smile
 
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