[TonyTheTiger57]

I have a 2018 SHO Performance Pack that I bought brand new. The car at idle, and while driving has a slight fluctuation in the idle. I can feel it and see it on the gauge cluster. I took it to the dealer. They can’t find anything wrong with it. They told me the car needs to break in. Well, 10,000 miles later, it still has this fluctuation. I’m unsure what it can be. No engine light or codes stored. I tuned the car, I changed the plugs fromSP534 to SP542, it has an AirRaid CAI I always run premium fuel.

 

[taucor0315]

Maybe a real good quality scanner can find the cylinder(s) that's misfiring? They make electronic tools to diagnose hard to find random misfires. One of those tools can detect if its an electrical misfire or one due to an injector that's not working properly.

 

[Jeff K]

Try switching back to the stock air intake system (which, BTW, is also a CAI) and see if the issue goes away.

You can watch missfires accumulate in each cylinder with Forscan.

 

[harveyspecter]

I have a 2018 SHO Performance Pack that I bought brand new. The car at idle, and while driving has a slight fluctuation in the idle. I can feel it and see it on the gauge cluster. I took it to the dealer. They can’t find anything wrong with it. They told me the car needs to break in. Well, 10,000 miles later, it still has this fluctuation. I’m unsure what it can be. No engine light or codes stored. I tuned the car, I changed the plugs fromSP534 to SP542, it has an AirRaid CAI I always run premium fuel.
Autoguysland shows that lost power or decreased gas mileage can cause a cylinder misfire. Visit Autoguysland website to read more this topic

This is special issue. Try to use good scanner tool to check the engine again.

 

[BC42875]

Run mode 6 and check for the misfires. It will only put a code out if the misfires exceed a threshold. One of my old posts had a write up on this.

https://www.taurusclub.com/forum/114-5th-6th-gen-maintenance-repair/176627-bump-shift-problem-solved.html

 

[taucor0315]

Again , if the engine on this vehicle has a slight miss ,especially at idle too, there ARE electronic tools to detect that kind of misfire. I've seen them on Ebay, in Auto parts stores, & on-line tool outlets. One looks like a "paddle" that you put on the coil pack that shows if a CP or the plug is misfiring.

Another product , that won the SEMA award about 5 or 6 years ago, for best new automotive diagnostic tool, that I almost bought , was a little more sophisticated. I had a misfire issue with a 2008 Impala ,that didn't show up on a scanner, but it turned out fairly easy to diagnose, it was those Chinese made E3 spark plugs. I can't remember the name of that award winning tool , but it was said to be able to detect misfires that were under the threshold of the OBD2 standards. It was said to be able to diagnose if it was more likely to be an injector , rather than an ignition problem too. There are a few ways to tell if an injector is causing a miss too.

I'll try to get the name of either product, but right now it eludes me.