Girlfriend just bought an 03 evo 2 weeks ago and randomly the other night it started bucking and now runs super rich at idle/cruise (10-11's AFR). I'll post the mod list and a few startup/idle logs, as well as what I've already checked and maybe someone can give me an idea of what's going on?


Mods are as follows- 2.3 with cosworth head and s2 cams, fp black, perrin intercooler, SD setup (unsure of what sensor as of right now) with a GM IAT, JGT 500 exhaust, supposedly FIC1450's, however, the scaling is 975 in ecuflash so I have a hard time believing they're scaled that low (haven't checked them). I have DEFI boost/fuel pressure gauges and an AEM uego.


Fuel pressure with the car running is rougly 43 psi, 38-39 with the car off. Vacuum fluctuates around -12 at idle. Boost leak test holds 20psi for about 30 seconds. I have 2 miniscule leaks from the j-pipe and throttle body gasket, but they are very small. It's well sealed up beyond that. We were running E85 when we bought it, but switched to 91 temporarlily (dual map). The AFR's haven't been real stable at cruise/idle since we bought it, I figured partially due to the IAT wiring coming apart.


We were leaving the gym the other night when it started bucking horribly (similar to a MAF going bad), shut down and restart yielded AFR's in the 10's and it was just doggy as can be. It's been that way since the other day anytime I start it up.


Here's a few startups/idle logs, maybe someone can see something going on? O2 is cycling, coolant temp sensor seems to be working properly, MAP sensor look weird to anyone (It seems weird to me). Apparently the wideband isn't logged to the ECU, which I'll work on hooking up today.

 

Just to update, pulled the plugs today and cylinder 3 was fouled with fuel. The other 3 looked normal. I'm going to assume the #3 injector is stuck open as cold compression test was 150psi across the board. I put fresh BR7ES plugs in, just need to take it for a test drive and see if/how quickly the plug fouls out again.


The plan is to bring it into work Monday and put it on my snap on solus and see if the computer is keeping the injector on or what. I wish someone would code an injector balance test into evoscan.

 

Who's tuning this? I'd probably get a new tuner or talk to them to see what's going on.

For instance, on the Alt map the inj are scaled to 975. Makes sense if that's on E85, but the timing is through the roof (26* up top) and the knock settings are set to mask knock. The main map, which has better timing, but still too high for 91 octane. The 91 octane map has the same injector scalings for E85. It should be 1329 for pump.

o2 sensor is basically maxxed trying to take away fuel. Plugs will foul quickly unless you get the tune under control.

 

The car was "tuned" by a local big name tuner known for blowing up cars on the dyno. I will be doing a road tune to get it dialed in better before I take it to a real shop I trust to put it on the dyno.

It's definitely not the tune causing my issue as the previous owner drove it as is for quite some time without issue.

 

E85 uses 30% more fuel than pump. That's why the injectors need to be scaled 30% more than pump. If it's stoich (previous owner drove it as is for quite some time without issue) on E85 with a 975 scaling, then on pump it will be @ 30% too rich with the same scaling.

I do this for a living. I'm sure it's the tune. It's possible that you have some other mechanical issues, but if you didn't it would still be rich on 91. No getting around it.

 

What I'm saying is that it was running perfectly fine on E85, and ran for a few days perfectly fine on pump 91. I know what you're saying, and I'm in the process of rescaling the injectors and adjusting since my map sensor (evo X 3 bar I found out today while working on it) is scaled wrong as well.

I also just noticed, alternate maps is set to kick on with the TPS on my ROM. In the glove box was a small black control with a toggle labeled "91" on one side and "E85" on the other. The previous owner didn't know it had a 91 tune on it, and when I found the box I assumed that was the toggle for alternate maps. I'm starting to wonder if that box was related to something else, wideband maybe? for switching, as we didn't use the TPS to change maps (since I didn't know how alt maps was setup on the car originally). Looks like im going to go chase wires and see where that box leads. I hate buying other peoples projects....