Smell of gas/exhaust fumes through vents

trailblazer077

Original poster
Member
Apr 8, 2012
2
Alright this is becoming very annoying for me now. I need help with diagnosing this problem I am having. Everytime I use my a/c without using the recirculate button I get the smell of exhaust and or gas coming through the vents. Can anyone tell me what the issue is that I am dealing with. A side note: I also smell exhaust underneath the driverside when ever the vehicle is warmed up. All filters, important sensors, spark plugs and wires as well as a new cat. converter replaced. Any ideas will be appreciated. By the way this is on a 04 TB LT I6 4x4, non EXT.
 

03envoy

Member
Dec 25, 2011
537
trailblazer077 said:
Alright this is becoming very annoying for me now. I need help with diagnosing this problem I am having. Everytime I use my a/c without using the recirculate button I get the smell of exhaust and or gas coming through the vents. Can anyone tell me what the issue is that I am dealing with. A side note: I also smell exhaust underneath the driverside when ever the vehicle is warmed up. All filters, important sensors, spark plugs and wires as well as a new cat. converter replaced. Any ideas will be appreciated. By the way this is on a 04 TB LT I6 4x4, non EXT.



This is just a wild guess, but possibly an exhaust manifold? Did you check that out yet?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Welcome! Saw your post on the other site. I'd take it in to a trustworthy muffler shop quickly for an exhaust test if you can't see it easily yourself. Carbon monoxide leaks are nothing to put off diagnosing because of the poisonous effect it has on everyone. The platform has had chronic problems with exhaust manifold cracking, but that's on the passenger side. But the fumes could waft over to the driver's side easily.

If you also smell unburned fuel hydrocarbons, get the catalytic converter tested as well for backpressure. Have you had any problems getting full power in wide open throttle (WOT) situations?

Ever any Service Engine Soon light flashing? Steady?

How many miles? Any other maintenance history? Are you current on plugs, O2 sensor maintenance, and all fluids? (Not that fluids matter, but I tend to ask new members a lot about that because many of them don't remember about the short 50K transfer case interval)
 

trailblazer077

Original poster
Member
Apr 8, 2012
2
The TB has 122000 miles on it. Mainly driven on the highway back and forth to work. All main sensors, catalytic converter, plugs, filters and fluids have been replaced. I have no problems running wide open. The TB actually runs great. Just smells of exhaust fumes. I have noticed a clicking sound coming from the passenger engine side. I do believe it could be the exhaust manifold. here is my question. How does the heated air enter through the vents? I have noticed that the only air intake entrance is through the port coming out of the air filter box.
 

Dillyo82

Member
Aug 17, 2012
80
I only get my smell from Close to WOT or WOT (Merging onto Highway). Read that the bolts on the Manifold come loose, break or the Manifold itself Cracks and causes this. Haven't had any issues from it though. It's been years now and has become an expected thing. I'll get a Manifold and/or bolt someday. It's always something else that has to be fixed first though.
 

OMGTruk

Member
Aug 28, 2012
11
Dillyo82 said:
I only get my smell from Close to WOT or WOT (Merging onto Highway). Read that the bolts on the Manifold come loose, break or the Manifold itself Cracks and causes this. Haven't had any issues from it though. It's been years now and has become an expected thing. I'll get a Manifold and/or bolt someday. It's always something else that has to be fixed first though.

i'm assuming this is on an I6. I don't have the I6 and have the same thing happening to me. Its a given that if i have someone w/ me i will have to roll down the windows to air it out. on a long trip if i average above 75 my eyes start to burn, a sure sign i'm about to die of CO posioning. :hissyfit:
 

JerryIrons

Member
Dec 20, 2011
434
Does it run louder than it used to?

I had a problem like this a while ago on an older ford pickup, it was solved by tightening down the bolts that hold the exhaust or exhaust manifold can't remember which.
 

Dillyo82

Member
Aug 17, 2012
80
OMGTruk said:
i'm assuming this is on an I6. I don't have the I6 and have the same thing happening to me. Its a given that if i have someone w/ me i will have to roll down the windows to air it out. on a long trip if i average above 75 my eyes start to burn, a sure sign i'm about to die of CO posioning. :hissyfit:

Yeah it's an I6. As long as I don't hammer it, it doesn't smell. I don't notice it being any louder either.
 

Badbart

Member
Nov 20, 2011
633
Any resolution to this problem? My 2004 TB (with 170K miles) had a coil go bad last month. Had it towed to a shop that works on my fleet. Replaced the #4 coil. Immediately started smelling exhaust fumes through the vents. Took it back, they went over everything they could think of under the hood. No leaks found, ran good, no codes. Expanded the search, found a vent going to the gas tank clogged with what looked like red clay?! Problem seemed to be solved. Checked fuel mileage. 13 mpg in town. Used to get 18 mpg in town. Took to GM dealer. Replaced OEM spark plugs. Fumes are back, have to run AC in cabin only mode. Side note TB used to idle smoothly, for the past two years or so you can feel a vibration at idle in drive. Replaced motor mounts, still vibrates. Will replace trans mount next. Seems to have good power, not skipping. All coils check good under power according to GM dealer. Any ideas? Hard to believe anything that has exhaust this rich isn't setting a code.
 

Mooseman

Moderator
Dec 4, 2011
25,494
Ottawa, ON
Get a Bluetooth OBD adapter and Torque (Android) to get some live data. Check the fuel trims as well as the O2 sensor. Check for leaks (you'd think the dealer would have done this) and fuel pressure. When shut off, it should hold and not drop. Clean the throttle body and disconnect the battery for 30 minutes to reset the PCM.
 

Badbart

Member
Nov 20, 2011
633
No gas smell at all. Smells like a 1963 Ford Falcon with the choke on! Just a rich exhaust smell. The weird part is i don't smell this coming out of the tailpipe. I hear nothing that leads me to believe there is any exhaust leak. I forgot to mention, I cleaned the throttle body last November and the tech at the GM dealer noted how clean it was. They did do relearn however. It would seem the rich exhaust smell would be a definite clue, but two different shops can't figure it out. the GM dealer hooked up a laptop and drove it to see if the other coils were breaking down under load but found nothing. I had intended to pass this down to my youngest son as it's been one of the best vehicles I've owned but this thing is whipping me.
 

Mooseman

Moderator
Dec 4, 2011
25,494
Ottawa, ON
I'd still get my own data. I don't trust dealers to do anything right except fill the washer fluid.

One thing that just popped into my head (must be lonely!) is the cat could be plugged. If possible, get a backpressure test done.
 
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Badbart

Member
Nov 20, 2011
633
That's a thought. I'll see what I can find out.
 

Tiggerr

Member
Jun 6, 2013
1,324
Perrysburg, OH
I'd still get my own data. I don't trust dealers to do anything right except fill the washer fluid.

One thing that just popped into my head (must be lonely!) is the cat could be plugged. If possible, get a backpressure test done.

That's what I'm thinking... has to be exhaust getting forced back into engine bay somehow....
 

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