tblanch

Recently I have been experiencing an exhaust type smell under VTEC only. I primarily drive with the top down. I can not smell any exhaust under normal driving conditions.

So far I have checked the exhaust for leaks and I did find that a nut had fallen off of the header. I retorqued the header but the smell remains. I also bought new seals for the valve cover as I thought that it may have been excess blow by. That also had no effect on the smell.

Does any one else have this same smell in VTEC only? Could I potentially have a crack in the header that only leaks under VTEC due to the higher exhaust pressure?

robb

I get a certain smell when I vtec it's hard to explain but it is not like a leaking exhaust smell. Is there a break in the header gasket were the nut came off?

zeroptzero

The flexible connection from the header to the exhaust is a common source of exhaust leak at the donut gasket, it flexes at WOT and VTEC pushes more pressure into the pipe to potentially leak out. That exhaust leak will come up and into the engine bay and cabin under certain conditions. Header gasket leak and donut gasket leak are the 2 main culprits. Lastly, people who put those ridiculous mini K&N breather filters on their valvecover incorrectly will get the same smell - crankcase fumes will push out and into the engine bay/cabin.

tblanch

So I checked the header to cat connection at the donut flage and there does not appear to be a leak at least at idle. Additionally, after torquing the header back down, there is no discenable leak coming from the manifold gasket area under idle conditions either.

If flexing during VTEC is causing the donut gasket to leak, is the best fix new engine mounts or possibly one of those torque dampers?

I am going to spray some soapy water on the header to see if there are any small leaks that im not finding. Thanks for the help so far.

zeroptzero

Yeah the donut gasket doesn't leak much at idle , it leaks as the engine flexes and pressure in the exhaust increases - ala VTEC. You won't notice a smell from the exhaust tips as that is further back, but odours like that are usually further forward , hence the reason I mentioned the donut gasket and header flange. If you haven't had the exhaust opened up the donut gasket doesn't usually leak much, it tends to happen after the exhaust system is opened up or swapped out and the spring bolts aren't aligned or tightened properly/evenly on reinstall. If the donut gasket leaks you will see carbon trails or drip marks around the outer edge. I wouldn't replace any parts until you can isolate the issue. An exhaust smell that mimics a motorcycle or lawnmower smell is a leak that is forward of the catalytic converter as it is exhaust gasses that are not treated by the cat. An exhaust leak after the cat smells different and would be very faint and less harsh than pre-treated exhaust fumes.

tblanch

The exhaust smell definitely has more of that lawnmower type of smell. It would make sense that the leak is either at the manifold gasket or at the donut gasket because I get the smell on in VTEC at speed.

The header is OEM but I do have an EVS high flow cat installed as well as an HKS hi power dual exhaust. When I replaced the cat, I used a brand new OEM donut gasket. I know Honda actually calls for new spring bolts but I elected to reuse the original spring bolts. I did tighten down the spring bolts fully and made sure that they were aligned properly before fully torquing the other side. I will report back once I have isolated the issue. Thanks!

noodels

Have you turned the dipstick 180 degs as maybe lifting up a tad.

tblanch

I have not noticed the dipstick being pushed out but it's worth a try.