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Running rich during errands

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What's up fellas

Lately I've been noticing a rich smell of gas inside the cab during running errands/heavy traffic after a fuel up...

Yesterday I was with my girl and even she was concerned about the smell, I instantly thought that it could be my o2 sensor but I know I have an exhaust leak in the exhaust manifold....

I checked at the gas tank and no leaking from the tank, no visual from the hoses,

Any other ideas?


Thanks in advance

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Fix the exhaust leak? My '92 had a bad one when I bought it....as in the previous owner had disconnected the header from the rest of the exhaust. Smelled like it was always running rich (O2 sensor always saw a "lean" condition due to no exhaust).


Sent from my SM-G930T using Tapatalk


Also, I'm not sure how applicable it is here with the 4.0 but certain exhaust systems do have a scavenging effect. This essentially pulls the exhaust from the cylinder, a leak in the header could cause fresh air to be pulled in, also causing the O2 to read lean.


Sent from my SM-G930T using Tapatalk

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If you're smelling them at slow, around town speeds it may be that your engine isn't getting hot enough to burn off the fuel in the oil.


Fuel smell checklist:


Check your plugs  If you have one spark plug that is ALOT cleaner than the rest, you may have an injector leaking internally.  This excess fuel can reduce the lubricating effects of the oil in your pistons by washing it off the walls as you drive.  A strong fuel smell in your oil may be another indicator of a leaky injector.


Look at your injectors and fuel lines while the engine is running.  A small fuel leak will and does evaporate by the time you turn off the engine and go look at it.  Look for "clean" areas around your injectors and fuel lines.  One little drip can make a whole bunch of fumes.


Look at your airbox Make sure the large vacuum hoses are connected and the grommets on the valve cover aren't cracked or broken.  Check that you don't have any hanging vac lines.


Look under your cab while the ignition is on.  When the fuel line is pressurized it can and does leak when the little hoses that connect the fuel filter get old and rot out.  If you stop the truck, get out and then look under it, if it's leaking there you won't see it.


Check the vent hoses and charcoal canister that are supposed to pull fumes out of the fuel tank.  They rot pretty badly and a leak there is all fumes, right next to the firewall.


Your girl is correct in being concerned about fuel smells.  If there is a leak in the engine compartment it's likely right over your exhaust manifold...which gets damn hot...Ka boom!  If it's just a vapor/fumes leak it's not as dangerous.


I had a vapor leak from a disconnected vac line that was very strong at hi speed.

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The 2.5 only has one injector directly above the throttle body,

You reminded me that I needed to replace my air box as one of the plastic pcs that connect to the top of the valve cover broke as I was in process to replace my motor mounts

The hoses at the gas tank and fuel filter are all brand new as of a couple months ago,

And the hoses at the charcoal canister are rotted to the fullest but didn't know they pull fuel fumes in, ill replace those as soon as possible...

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I missed the 2.5 part. But, the vac hose from my valve cover to my airbox was off and I was getting bad fumes in the cab.

I just saw this morning where the fumes were constantly coming out of the hose from the valve cover and pretty much filling the engine bay with fumes and I'm sure into the cab....

Also, noticed my throttle body is sweating, is it normal?

When I tried to smell the wetness it didn't smell like anything

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  • 6 months later...

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