Dieseling sometimes when hot

[chevytech87]

Those 2 items [RPM and octane] are likely enough to cause dieseling.

As much as it hurts, I use E free or high octane in the SB. Depending on the year today's high octane is actually lower than regular used to be. Everyday 30 cents a gallon regular was 94 or higher until they started to take the lead out.

So try the 93, see what happens? I know this topic has been beat to death but is it worth looking into some sort of additive?

 

[fast 99]

So try the 93, see what happens? I know this topic has been beat to death but is it worth looking into some sort of additive?

Yes it won't hurt anything. New engines run hotter for the first few thousand miles.

Don't know what additives work. Some of it is likely snake oil. I have a couple high compression vehicles and use AV gas, but you shouldn't need to go there. AV gas will ruin the O2 sensor.

 

[chevytech87]

Yes it won't hurt anything. New engines run hotter for the first few thousand miles.

AV gas will ruin the O2 sensor.

Good to know, didn’t know that about AV gas!

 

[JBswth]

Hey all,

I’ve been driving my truck this week to break in the new motor and get a feel for the sniper EFI. Overall, been pretty happy with everything! I have noticed that sometimes, when the engine is at operating temp after a decent drive the truck “diesels” for a second or two. I’m thinking this may just be an idle screw/ IAC issue? First time I’ve tried to use this system and it’s a lot to take in. Any suggestions?

CTS shows ~183, I am running 87 right now, so I suppose that could be an issue. How lean is too lean at idle? I think I’m sitting around 13-14:1. Idles at about 800

800 RPM is too high, unless you have a pretty hot cam. Try slowing it down to about 500 RPM in Drive, (automatic), or 550 with a stick.

J. B.