Car

2003 Evolution

Upgrades
Boost Controller
Boost Guage
K&N Air Filter
Gen 1 S-AFC (Apex-i)

Temperature outside = 90+ Humid

Today while driving to work I went to pass some slow drivers. I down shifted into 4th from 5th at 55mph. When I put my foot to the floor the car shuttered violently then jumped forward. This felt like fuel cut, but my boost is only at 19 and holding firm. I had the boost controller put on by AMS (www.automotosports.com) and has been fine since then except for today.

Does anyone have any ideas on why fuel is cutting? Should I turn my boost down on really hot and humid days?

One recommendation was to upgrade my fuel, but I was told I wouldn't have to if I didn't run more than 19 psi.

 

That doesn't sound anything like fuel cut. Do you know what fuel cut is, or were you just guessing that this is what it feels like? Fuel cut is when you hit full boost and suddenly the ECU cuts fuel completely causing the car to nosedive. It feels like you hit a brick wall, and you have 0 power whatsoever until you let off.

On the flipside, I can't think of what would cause the shuddering other than a clutch issue, but that's not a slipping clutch.

 

Check your plugs.

 

i have had that happen nuromus times. It does feel like you hit a wall but the car goes after that. it was usually when i would be in fourth gear

 

My car would hit fuel cut on COLD days from a slow roll at max boost, usually around 3000 RPM. It was a real pain in the *** trying to pass people on the highway. I fought with it for quite some time till I finally got 650cc injectors and leaned the AFC out.

Dunno if this is what's happening to you but basically the ECU sees crazy high air flow and cuts the fuel. It happened for just a split second and it would often resume before I could get my foot off the gas in the EVO.

Now with the leaned out AFC settings the ECU doesn't 'see' the same amount of air being flowed and hasn't given me one problem since.

 

I had the same problem today but mine was due to forgetting to unplug the windeband controller on my car..heh! Live and learn....

Anyway, what octane fuel are you running?

 

93....

 

Either upgrade the fuel and tune it so the ECU doesn't see the same air flow or flash the ecu to eliminate fuel cut. It was very difficult for me to track down the issue because flashing the ECU seems to be one of the first things anyone does on these cars and as such virtually no one has ever experienced the problem.

Bigger injectors and the AFC2 taking at least 9% out has completely resolved the issue for me. No, you don't need bigger injectors to make more power at 19psi, but with the leaner fuel settings the ECU doesn't think you're flowing as much air...