Recently, I have smelled raw gas smell and slightly sluggish performance from my 2003 Monte Carlo LS (competition) 3400 HO. For example, yesterday after driving in 112 degree day in city traffic in Las Vegas I noticed the poor performance (almost like the engine was weighed down). I arrived at my destination and smelled strong raw gas when I got out of the car. A couple of days earlier I parked the car inside the garage and noticed a strong raw gas smell when I went back into the garage. I looked everywhere for leaks and opened the gas cap, nothing. I think it might be coming from the exhaust.I actually had to open the garage door and turn on the fan to help vent the garage.My Monte has 47000 miles and has no modifications to the engine. I ran fuel injector cleaner through the gas a couple of tanks ago; I noticed a decrease in gas mileage but since than the mileage has returned to normal. The smell seems to happen with the lower engine performance and at operating temperature on hotter days.
Several oil changes ago I had to drop the red coolant because it had clayed up, but the clay did not make it to the water pump, as I checked the inlet and seemed clean. I replaced the red with yellow coolant and seem to be a little dirty still, I might drop this coolant and flush the system again and replace it with yellow again. I only mention the coolant because, hotter engine temperature led to poor gas burning. The gas smell has me concerned, I almost want to take it to the dealership, but the problem seems to be erratic. Any help out there? Thanks in advance!

 

If you're smelling fuel you probably have a leak somewhere. I would start in the engine bay and look at all the injectors, the fuel rail, lines leading into the motor and check for leaking fuel. If your coolant gummed up then there is another issue. The 3400's are known for intake/head gaskets leaking and failing. I would also check fuel line pressure.

 

Thanks for you post!!! I will check some more… It would be hard to find if the fuel is evaporating. When I noticed the smell in my garage I opened the hood and smelled around as well as looked for leakage and saw and smelled nothing. I would think I would smell the gas in the cabin if I had an engine gas leak, no? I don’t have any idiot lights either. The smell seemed to be stronger towards the rear of the car, not leaks under the car. This kind of acts like catalytic converter, injector or spark problem, especially since it doesn’t happen all the time. What to do think?

 

That's a good point about the fuel evaporating. As far as smelling it in the cabin, sometimes you will and sometimes you won't. I don't think it is a catalytic converter issue, because normally that would smell like rotten eggs if that was going bad. You don't have a Service Engine Soon light (or Check Engine Light)? Is it only when you are driving that you notice it the most or when it sits? I might not park in the garage for a while until you find this source because if you can smell fuel it will ignite. If it was a spark problem you would be misfiring and my thought is that if you smell it toward the rear of the car, maybe you're not burning all of your fuel and it is reaching the muffler and tailpipe. If that's the case that could mean your timing is off or your fuel pump is malfunctioning and sending too much fuel through the cylinders or your computer is not working properly...if any of that was happening though I think you would have a misfire on one or more cylinders. Even though you may not have a service engine light I think I would take it to an auto zone or some place like that and see if your computer has stored any codes. Keep us updated!

 

I am heading to AutoZone for a code reading. I have a theory, maybe you guys can help me with it. Does the 2003 3400 have Teflon rings around the cylinders? If the Teflon wears won’t that allow gas to get by the rings?

 

no codes

 

No codes...hm....I've heard that about teflon rings and I'm not sure if the 3400 does or not. This really isn't a problem I've heard about on these...lol. I would take it in to a trusted shop and see what they think.

 

Well you are not going to believe what the problem was... I just got the car back from the dealership (still under warrenty) turns out it was a cracked gas cap! I looked at the gas cap, everytime I fuel... anyway one $75 gas cap... thanks for the advise!

 

It's always the simplist problem! LOL.

 

I had this same problem. Every time i would eat at Taco Bell I'd get this raw gas smell that seemed to be coming from the interior of the car as I drove it. It even followed me into the house and would come and go throughout the night.I quit eating at Taco Bell and the smell went away.