Roush supercharged, now idles rough at start up then smooths out

[Mansa M]

I am also having this issue and my car has 36k miles

I will change the vvt and vct solenoids since they will fail eventually in the futur. I will keep you posted if it changed anything.

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[23RoushGT]

I have a 2023 with the Roush supercharger kit installed by Ford. I am the second owner but the first owner hardly ever drove it (I found his info in the glove box and talked to him multiple times since I’ve had it). It has about 19k miles now and I bought it about 5 months ago. I thought I did enough research before I bought it and knew the cats had to go but had no idea about the low idle/start up. I took it to a shop that specializes in mustangs and had long tube headers and high flow cats installed. After that I thought everything was fine until I started it after getting gas a few days later and it did this low idle thing for about 5 seconds then cleared up. I got online and found this thread. I called the shop and explained what was going on and that it would only happen randomly and only after my car was warmed up, never on a cold start. He said when I bring it back to get tuned he could turn up the idle on start up and it should resolve the issue, he said he’s heard of this happening to others and that was the only way he knew to fix the problem. I later took the my Mustang back to him and he tuned it and I haven’t had it happen since, this was about 2-3 months ago. I wanted to wait and make sure it didn’t happen again before I said anything in this thread and it wasn’t a fix but so far I haven’t had it happen again.

 

[robvas]

If your tuner has to crank the idle way up, they don't know what they're doing.

 

[23RoushGT]

If your tuner has to crank the idle way up, they don't know what they're doing.

Never said he cranked the idle way up, I said he turned it up just enough that I no longer have the problem, car starts up and runs smooth like it should every time. By all means don’t do what I did if you think it’s a problem but I haven’t see another solution in this thread.

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