Exhaust smell in the cabin on idle with heater/AC fan on

[genetixx01]

Hi Genvibers,
I’m wondering if there are still some folks here. It used to be my main source of information when the time came to fix my Vibe, so hopefully some people are still here! I’m having a problem that I can’t manage to resolve myself and for which I’m now clueless, so I’m trying here if you guys can give me some help.

My car is a 2005 Pontiac Vibe with the base engine. There is a smell of exhaust that enters the cabin when the car is on idle (at a red light for instance) and the heater fan is on (whether it’s for the A/C in summer or for the heater in winter). When I’m driving with the fan on, there is no smell and when I’m on idle and turn the fan off, there is no smell either.

Several research pointed out a leak somewhere in the exhaust system starting in the exhaust manifold. To troubleshoot it, I taped a shopvac in blowing mode in the exhaust pipe, and I sprayed soapy water all along the exhaust line. I could detect small leaks at both donut gasket, the rear flange and the one between the exhaust manifold and the first catalytic converter. The leaks were not that bad, and one would assume that there is a certain amount of leak all the time in these joints, but anyway, not seeing anything else I decided to replace both donut gaskets. It was a hard job because the bolts and springs were rusted. But with a lot of effort, PB Baster and heating, I managed to replace both donuts and their bolts & springs. I took this opportunity to repaint all the line from the resonator up to the tail pipe since this section is aftermarket and was rusted (living in Canada). By the way, I need to specify that I couldn’t find any leak on the exhaust manifold, despite it’s not easy to check for leak on it. In addition, I’m not hearing any clicking noise characteristic of exhaust manifold leaks.

Then, I reinstalled everything and I tightened the bolts as much as I could. Unfortunately, the smell problem in the cabin was still there. It is maybe slightly lower than before, not sure, but it’s still there. I checked again with the shopvac and the soapy water and I could still see bubbles near the donut gaskets. I was a bit frustrated, but I started wondering if it’s possible to completely remove any small crack there. After all, these are mobile parts so should we expect absolutely zero bubble when pushing string air from a shopvac? I would certainly like to check on another car without issue to see if I can see bubbles the same way…

So now I’m kind of clueless on what could be the problem. The donuts and bolts are new, I can’t see any leaks in the exhaust manifold, I don’t know where to look now. I discussed that with my local garage and the guy said that he would not know what to do more than what I did… This is why I’m now asking the community, in the hope that someone here has seen this problem before.

Hope to read you folks!

[andrewclaus]

How many miles/kms are on your car?

I've replaced two of those spherical joint gaskets on two separate old cars in the past two years. Neither one had an exhaust odor I could detect in the cabin--the only symptom was noise, and I didn't do before/after leak tests. On the Vibe, it was the rear joint, and I also had to replace the resonator and pipe because the flange had eroded through. Could corroded metal at the joint be part of your problem?

And I'd get a CO monitor in the cabin. Could it be possible you're actually getting a burnt oil smell instead of an exhaust leak? I've also had to fix two oil leaks on the front of the Vibe's engine--the timing chain tensioner and the front pulley/timing cover seal.

[joatmon]

Do you get the smell at those conditions but when the HVAC is set to recirculate?

Have you looked at the integrity of the gasket under the hood between the engine compartment and the air intake at the bottom of the windshield?

How is the cabin air filter?

[genetixx01]

How many miles/kms are on your car?

I've replaced two of those spherical joint gaskets on two separate old cars in the past two years. Neither one had an exhaust odor I could detect in the cabin--the only symptom was noise, and I didn't do before/after leak tests. On the Vibe, it was the rear joint, and I also had to replace the resonator and pipe because the flange had eroded through. Could corroded metal at the joint be part of your problem?

And I'd get a CO monitor in the cabin. Could it be possible you're actually getting a burnt oil smell instead of an exhaust leak? I've also had to fix two oil leaks on the front of the Vibe's engine--the timing chain tensioner and the front pulley/timing cover seal.

Thanks for your quick reply @andrewclaus,
The car now has 290 000 km. As I mentioned, I already replaced the resonator and the muffler two years ago because the flange was broken (I should never ever have replaced these original parts with aftermarket crap, but at the time I was told that this was the only solution. This aftermarket crap is rusting as hell and I need to sand and repaint it every 2 years...). Anyway, there is no rust on any part of the line now, so corroded metal cannot really be part of the problem.

"Could it be possible you're actually getting a burnt oil smell instead of an exhaust leak?" This is an interesting question. Although I'm not 100% sure, I'm still pretty confident that this is not the smell of burning oil. I do have the famous leak of the timing chain tensioner (like every Vibe), but I have had this oil leak for as long as I can remember (despite changing the o-ring from time to time) and I never had this exhaust smell before, so probably not related. Installing a CO monitor would probably be a good idea, but as I said, I'm still pretty confident this is an exhaust leak. I can also sometime smell some exhaust odours when I'm outside around the hood, and this make me thinking that there is a leak somewhere, but I don't know if this is just normal odours and if I'm overthinking this issue...

[genetixx01]

Do you get the smell at those conditions but when the HVAC is set to recirculate?

Have you looked at the integrity of the gasket under the hood between the engine compartment and the air intake at the bottom of the windshield?

How is the cabin air filter?

Thanks @joatmon for your quick reply!

Ok, first, I no longer have the mode recirculate available because the little engine that control the opening and closing of the air flow with the outside (can't remember the name of it) failed about 5 years ago. I was making a constant clacking noise, and I decided to just unplug it and keep the car always on normal (not recirculating) mode. But I was thinking about going to the scrapyard to get this part and to see if I do have the problem in recirculating mode. My guess is that I would not, but I can't tell right now.

About the air filter, I just replaced it with a brand-new Frame air filter to see if it would fix the issue. It didn't.

I'm now curious about the "gasket under the hood between the engine compartment and the air intake at the bottom of the windshield". Are you talking about the rubber gasket that get exposed when we open the hood? This gasket as been completely stretched out for as long as I can remember. You think it could be the issue? I kind of feel it has always been that way, but I could probably give it a try if I could find this part somewhere. I'll go check it again more carefully right now just for fun.

[joatmon]

I was asking about the long gasket or weatherstripping on the top of the firewall side of the engine compartment. The cabin air intake is right behind it, if that gasket doesn't seal, then any vapors in the engine compartment would get sucked into the HVAC system, more pronounced when not moving. I don't think it needs to be a perfect seal, but if its worn, or the hood is misaligned and doesn't compress it, or if there are foreign objects on it, then you get more engine compartment air sucked inside. Ideally you wouldn't get exhaust in the engine compartment, but it might be why its getting into the cabin

hoodgasket.jpg (39.85 KiB) Viewed 744 times

[genetixx01]

Hi @joatmon,
Thanks for the picture, this is exactly the seal I had in mind. As I said, it is stretched and form some sort of ware that makes it much less of a seal, and I will try to fix that to see if this fixed the issue and will let you know, but I feel it's been like that for so long before the smell problem appeared that I have some doubts that this would cause the issue. I think you mentioned the most important thing when you said, "ideally you wouldn't get exhaust in the engine compartment". I think the problem is more there. Why is there any exhaust fume in the engine compartment.

[genetixx01]

Something else that I came up with as a potential explanation this weekend is the following. For a while, I had a problem with a lean fuel mix. An engine code like 071 or something like this. It took me a while to figure out what it was, and it ended up being an actual hole in the engine air filter... (yeah I know, don't ask me how I got this hole and don't ask me why I didn't check this in the first place). Anyway, changing the filter resolved the problem, but I probably drove a few thousand km with this hole. I then leaned the injectors, and now everything is fine, but I'm wondering is this could have restricted the catalytic converters. I'm wondering if a now restricted catalytic converters could explain that the exhaust manifold has difficulty to push the gas through the cats which would cause the exhaust fumes to remain in the engine compartment.

I'm saying that because I experiment other symptoms of bad catalytic converters like week acceleration and sometime rough start. I don't experiment any rotten egg smell, though, and I don't have any check engine light on. I watched some videos on how to clean a restricted cat with soapy water, but I'm seeing contradiction on how this can help or not.

[Capt.Vibe]

You could have one of the 2 converters that is clogged or blocked. A lean fuel mix will ruin a cat. I know you mentioned it was replaced but I would replace it with a good quality aftermarket unit. I know you want original but cost of that part OEM from Toyota would probably exceed the value of the car.

[genetixx01]

Hi @Capt.Vibe,
Thanks for your reply! I did run on a lean fuel mixed for probably a bit too long, so yes, I do think it would be the catalytic converters that are clogged, but the car is a 2005 with 285 000 km, so before thinking about investing in new cats, I would at least want to be certain that this is the problem. Do you know how I could validate this assumption? I don't have any check engine light, and no rotten egg smell.

By the way, I mentioned that I replaced the exhaust line, but I didn't replace the cats, I cut the line after the cats, before the resonator and I only replaced the line after the resonator.

Also, before investing in new cats, since the car is very old, I would probably try to clean them. I have seen a couple of tutorial and YouTube video online about that. I'm sure this is far from ideal, but I'm ready to give it a try. Is there any of you that already tries to clean a cat on a vibe or on other car?

Thanks!

[Capt.Vibe]

I have no idea how effective a cat cleaning would do but you would need to disassemble and remove everything to do it. At this point may as well just install new cats. I just replaced the entire line from manifold to tail pipe for $1000 because of rust and holes. There were cheaper options too. Auto Shack has both cats for $200 not sure of the quality though. Installation maybe another $150-$200. Should be good for a few years. If your car is otherwise in good shape I would not hesitate to invest in new cats.