Slight gas smell idling

[PowersOf12]

Can these Hemi's run "rich"? There appears to be a slight fuel smell from the rear when idling for say 5 minutes & exhaust looks clear. Sure, the old Hemi has 169,000 miles on it, but idles good (no surging, no bouncing on the tach, etc.).

I did put a bottle of Techron High Mileage fuel cleaner in before the last fill-up with 91 octane because the 87 stuff was out during the hurricane. Maybe that is burning funny?

 

[Brandon7]

What does no bouncing on the tach mean? I have a smell as well, trying to figure it out.

 

[Burla]

we don't have carbs anymore so these engines run by sensors and regulators. You can get a uoa and see if any fuel in oil. How many miles on plugs? si-1 thread.

 

[Dean2]

Could easily be a leak or your tank venting. Can you smell gas when it isn't running?

To tell if it is running rich enough to smell gas, hook up an MX+ and the readout will tell you if you are running rich. If you are running rich enough to smell raw gas you should be getting codes because your 02 sensors aren't doing their job.

 

[PowersOf12]

So, this has gone away. All I can assume is that it was the engine adjusting to all the stuff I put in (better octane gas for the first time and fuel system cleaner)? I am back on 87 octane and all is well. As for the no tach bouncing, I meant it was idling smoothly. I will just keep a nose on it. Thanks

 

[Burla]

Your truck is tuned for 89, but everything adjusts for higher octane or whatever is thrown at it such as low o2 or higher o2, your truck makes small adjustments to fix ratio. However, I am not sure your truck adjusts to 87 even though they say it is ok. What they mean is your truck is going to run less efficient but it is ok to run an engine like that. Just remember that if as your tank has less of what you had on it and more 87 if it comes back, it is hard for an engine to compensate for lower octane gas, it has to adjust spark timing which means it simply is not running as intended but hey it's still running.