CO Poisoning

I purchased a CO detector yesterday because I had a suspicion that I was being poisoned given the random acute headaches. I went out for lunch today and noticed that my CO detector read 44PPM. Has anyone ran into an issue like this? I have a spoiler on the back of my '68. I’m thinking that the spoiler is creating a vacuum that is sucking the CO into the car through the trunk. Any ideas?


Good catch! Immediately suspect is the exhaust itself. Assuming you have a complete, factory exhaust with no leaks, turndowns in the proper location, etc., I’d check next for holes in the body (trunk drop-offs/floor pans). Does it get better if you have the interior vents open/windows shut?

I never heard of spoiler cars having this issue.

I would replace the trunk weather stripping. Also I would look at the sealant around the tail lights.
Do your exhaust tips point strait out the back or down towards the ground?

The exhaust tips are flush with the angle of the rear bumper. The exhaust in front of the muffler is stock but everything from the muffler back is aftermarket (flowmaster 40’s/ unknown tips). I replaced the trunk weather stripping/tail light gasket a few weeks ago as part of a separate project. The CO level drops with the windows down but rises with the A/C on and the windows up.

The reason why I suspect the spoiler is because the previous owner installed it backwards (thick part of the spoiler is at the rear instead of the front like a wing) and painted the car with the spoiler attached. To correct the spoiler would mean cracking the paint which is something that I want to avoid if at all possible.

What a great idea to pack a CO detector in our old heaps. I know if I get stuck in traffic in my Moosetang things get pretty stinky in the cabin.

The AC air intake is the cowl vent. You might be getting CO from blow by being vented out under the hood, The rear hood seal will help this but if you have a lot of blow by you need to look into fixing that and it means a rebuild…

Thanks for the replies. This issue has been going on since I got the car (even before installing the Vintage Air system).

I have been chasing a similar issue in my 68 for years. Replaced trunk seal, rubbers, sealed behind the seat, firewall sealed, exhaust replaced. Problem existed with current rebuilt and previous engines. Only thing I can put it down to is that I have GTE style exhaust tips, rather than turndowns

This is why I think sealing off the trunk/back seat should be high on the list for any owner.

Bill, I’m going to go this route. I think I’m getting a lot of blow by. There is no smoke but I now think that the CO is coming from the exhaust fumes from the engine. If I drive the car for more than 20 minutes and go in the house I smell like I have been in the garage all day with the door closed and the car running. I feel that it might be bad oil rings on the pistons. What would I need to rebuild in the engine?
Thanks, Justin

Holes around the cowl vents.
Rubber plugs missing from firewall.
Rubber seal around accelerator linkage, speedo cable wore out.
Caulk missing around heater core pipes a/c lines.
Leak around shifter shaft.
Trunk floor rubber plugs missing or cracked.
Clogged or broken PCV valve.

Just a few things I’ve done in the past for that ‘old car smell’.

Make sure that your hose is connected from the valve cover breather to the air cleaner tube.

Sometimes the foam seal in the tube-in-tube steering column deteriorates and let’s fumes come right up the column.

I just kind of figured it was like the stuff on my grill grates. Kind of adds to the driving experience, much like the stuff on the grill grates gives the meat more flavor (lol). The buzz I get reminds me of high school :mrgreen: . My co worker’s brother was falling asleep every time he used the heat in his car. Found a pinhole exhaust leak right by the inlet.

Thanks for the replies. Are you talking about the hose from the PVC valve? If so, the hose is going from the PVC valve directly into the carb. Is that the correct configuration?

Can I send my MIL over for an extended drive?

No I am talking about the drivers side breather cap where you put in oil. Most of the cougars have a hose from that cap to the air cleaner.I have noticed if I leave my hose unhooked I smell oil & engine smell. Of course this is a engine that has 135,000 and never been rebuild and has a little blowby. It usually has a bit of oil in the bottom of the air cleaner.

Agree this is likely the problem.

Thanks for the replies. Where does the blow by vent? I don’t have a vented oil cap and I have a PCV installed on the other valve cover. If it is blow-by, what would I need to rebuild? I installed a trunk to cabin metal divider from WCCC but that didn’t do anything. I did a test drive today and I hit 72ppm which is about 30ppm more than the last highest reading. Thanks

Blow by is from worn out piston rings or rings that some how aligned their gaps. The combustion gas goes into the engine block and since its under pressure it has to find its way out. Before the PCV system the gases went out a draft tube into the air. The gases can escape out the oil filler cap because this pressure is greater then the suction through the cap from the PCV system. Also it will blow out around the rear main seal causing the famous ‘rear main oil leak’. The only permanent fix is a rebuild. For a visual of blow by gases I heat the engine up for slow idle and remove the oil fill cap. If excessive smoke starts coming out of the opening then the PCV valve can’t supply enough suction or the blow by is too great. There is a company Mewagner that makes an adjustable PCV valve to increase the suction and could reduce the blow by that happens when idling.