Rousch 427 EFI rough at 2krpms
 

My EFI Rousch 427 seems to run a little rough between 2200-2400 rpm’s. No hesitation or bogging just seems a little rough. It hasn’t lost any power or throttle response. Feels almost like a vibration only at the stated rpm’s. Not tires seems to be coming from drive train .

Your problem is likely rooted in the Accel DFI fuel injection that Roush used.

While you might be able to find aftermarket service providers still available after Accel terminated their support of the product, it is/will become increasingly difficult. Even when you go to the Accel site and click on their DFI and Service parts link, the only thing that shows up is a fuel pressure regulator for a 1986-1993 Ford Mustang/Mercury Capri 5.0L V8. Not a single Accel DFI component/part!

It is time to replace your Accel DFI unit with a more modern aftermarket alternative. The two best-featured / best-priced units are the Holley and MegaSquirt products. I have a Mega Squirt preference. That said, the Holley unit is a very good EFI system.

Both are relatively easy to install and will serve you well. Get rid of the old Accel DFI unit before it leaves you by the side of the road somewhere near a town called Racoon Run. (Racoon Run is just a few miles SW of Possum Creek Gulch.) Neither is a good place to have your EFI fail.

I have a fast 1.0 EFI

Do you have the faux 8-stack?

I had a Roush 427IR (Fuel injected 8-stack) with the Accel system mentioned and it took a year, shipping the car back to Roush, and then spending another 2K with a tuner in Fort Collins. The tune that Roush put on the system was not complete. It was firstly done on a Mustang with real mufflers (and back pressure). But it was not completely finished in that they never populated the altitude compensation table. I found a tuner that was trained at Accel on the system and tuned it on a dnyo and then did a 10K+' refinement on the altitude table and I was happy. I offered that tune back to Roush for my expenses but they never did anything.

If you have the faux 8-stack there is a small issue with the blending of the tables. As the throttle bodies open towards WOT, the air flow becomes straight in and doesn't get any turbulence as a result of flowing past the throttle flap. The result is that there is an incomplete air/fuel mixture and the engine starts to run rich. At that point in the throttle the FI system needs to lean out a little and then progress up again... This was part of the problem with the Accel but I imagine it happens with any of them, and this effect will really confuse self-learning systems...

That said, if you have a FAST system how old is the engine? Might it still be under warranty???

If your EFI skills are limited, the short way home would be to find a FAST reseller and ask his tuner for guidance.

No stack and the car ran flawless so the tune must be good

So to confirm this behaviour is a recent development? How long had it been operating OK?

It’s been running great for 5 years. You won’t notice it but I do since I drive it all the time . 6k miles so far

Replace your plugs.

Do the headers need to be removed to replace the plugs?

Also, use wires with ceramic boots to prevent heat damage.

https://www.summitracing.com/parts/maa-947c

I also used boot protectors to help protect the wires

https://www.summitracing.com/parts/sum-350119red

https://www.dropbox.com/scl/fi/4bbc0...obtfs7bzi&dl=0

No, just might need a flexible socket and wrench.

Gary,

You have strayed into the deep end of the swimming pool before you have learned how to swim. It might be to your advantage if you went to a FAST reseller and had one of his preferred tuners address the problem.

It is not hard to unintentionally hurt the engine and drive up the ante at the poker table when you didn't intend to.