strong fuel smell, rough idle

[19dabeast85]

Don't jump on me for not searching, can't exactly find my same symptoms with search results.

Recently (last 2 weeks) I've noticed a very strong "old fuel" smell in the cabin ONLY when:

1. Engine hot, and
2. At a stop, and
3. A/C fan on

There is no noticeable external fuel leak, checked injectors, rail, filter area, and driveway. Gas mileage seems to have dropped slightly though.

The engine idles rough but all 4 cylinders are firing (verified by pulling one plug wire at a time). I unplugged the vacuum line to the fuel pressure regulator and it does not smell of fuel. No noticeable idle change with it unplugged (and IM vacuum port blocked).

The exhaust smells like burned gunpowder, similar to the smell after launching fireworks or shooting a gun. Not normal, but no idea what this smell means.

Maintenance items:
1. cat is an O.E. replacement Magnaflow brand
2. o2 sensor is NTK replaced one year ago
3. Plugs are Denso Platinum TT stock heat range
4. Fuel filter is Purolator PureOne with 28k-30k miles (red flag for rough idle but doesn't explain strong fuel smell)

Relevant Modifications:
1. H23 I.M.
2. Cracked DCsports header (cracked at union of 2 primaries)
3. Blocked EGR with valve still plugged in
4. FITV blocked off
5. Air boost valve blocked off

Thanks alot for any help!

[19dabeast85]

Anybody?

[stretch JDM]

how long have you had the magnaflow cat. in bro ?

[ChampCoupe]

did you check the fuel lines? double check the lines on the fuel filter to make sure they are tight. Also you said there was no leaks around the fuel rail???

[19dabeast85]

how long have you had the magnaflow cat. in bro ?

3 years

did you check the fuel lines? double check the lines on the fuel filter to make sure they are tight. Also you said there was no leaks around the fuel rail???

Like I said, checked the fuel lines from the top, haven't crawled underneath yet but will tomorrow. And no leaks at the fuel rail, injectors, or regulator.


The weird thing is it's not a "fresh" fuel smell, it smells like REALLY old fuel. I drive about 15k miles a year so it has fresh, good fuel in it. I've filled up at various stations since this problem so it's not a fuel source issue either.

[ChampCoupe]

i am thinking you might have an injector thats stuck open... try reving the motor to see if you have a white smoke coming out the tail pipe.

[19dabeast85]

i am thinking you might have an injector thats stuck open... try reving the motor to see if you have a white smoke coming out the tail pipe.

No smoke and an injector stuck open would flood a cylinder on shutdown, it starts up just fine. Also, I can hear each injector ticking on time with my stethoscope. Seems a stuck injector wouldn't tick.

[old honda tek]

check your charcoal canister might be bad and full of gas.....

[Losiracer2]

you said your DC header was cracked correct? try swapping in an A4 header or whatever's available. It has to be coming from that exhaust leak, esp. if its cracked in 2 spots.

[19dabeast85]

I think I've narrowed it down:

The base idle was at 500 rpms which explains some of the rough idle issue. Set the base to 650 but now the engine idles at 1,000 with IAC, possibly a bad IAC valve?

There is an exhaust leak just behind the cat which MAY explain the smell at a stop, not sure how it's getting through the car AND layers of sound deadening but I guess it can.

The weird thing is the in-cabin smell and the smell at the exhaust tip are different which leads me to believe the after-cat leak is NOT getting into the cabin.

The only thing I can think of is the minutely small crack in the header is leaking enough that the radiator fans are blowing the leak into my A/C vent pickup, Bisi header please hurry!!

I also check the charcoal canister and it seems okay. I popped the small "lid" off the top (has a vacuum nipple from black box) and the rubber baffle inside there under the spring has a crack in it, will this cause any issues?

I went ahead and installed a different MAP sensor from a smooth running parts car I used to have and reset the ecu. I'll post back in a few days if the smell comes back.

Is there anything I can wrap the header with to seal the crack?