evoviii2jk

Not necessarily the dyno, but when you get on a dynoed with a reputable tuner he will hook up a wide band O2 sensor to your tail pipe to make sure he gets everything right

Synthetik

Let's correct a few things here.

Running lean means there's too much oxygen and not enough fuel causing whats called detonation or pre-ignition. Basically the fuel is igniting sooner than it should be. To rich means there is too much fuel and not enough oxygen. A good way to destroy cat converters.

A full throttle pull on a dyno is not going to show if you're leaning out at partial throttle. At full throttle your ECU is in what's called open loop. Meaning it's not reading data from the O2 sensors in the exhaust. It's pulling from a predefined table that's programmed into the ECU itself. This same open loop condition is also in effect on a cold start until the motor gets up to operating temperature. At partial throttle the ECU is in closed loop. Meaning it's pulling data from the O2 sensors in the exhaust and adjusting the amount of fuel injected into the cylinder on the fly. You could try to have the shop monitor the AF/R under normal cruising RPM. You won't be able to simulate real world conditions such as changes in air temp, elevation or inclines but it's better than nothing.

You could also try to get your hands on a scanner. Hook it up to the OBD-2 port and monitor the knock sensor while driving and see if the ECU is pulling timing. If it does, you're leaning out.

There's two ways to fix a lean condition. A new tune or a higher octane fuel. As far as I'm aware (someone correct me if I'm wrong), there is no way to load a truly custom tune to a JK. The 07 - 10 guys have the option of SuperChips and the likes but those are still only canned tunes. The only way to custom tune these pigs at the moment is with a stand alone. You'd be looking at a lot of wiring and a lot of money. No where near worth it on a stock motor.

Now, you said you're already running the SuperChips 93 tune and you're hearing popping? Are you sure you're hearing a popping sound or rattling? Rattling is usually what you hear when you run lean. Sounds like a bunch of marbles being bounced around in a can. Popping could be backfiring. Two different issues.

Stupid question. Are you running 93 octane fuel with the 93 SuperChips tune? Are you perhaps in a area that's at a really high elevation?

jaybrown

94 octane. I have a cai mbrp exhaust and superchips. That's it. I only started this thread because a guy said if I run a cai I run the chance of being lean and if I run the higher tunes for sure Only slight backfiring. Sounds good tho not big bangs. I think it's normal exhaust sounds

jaybrown

I also run 5w 30 royal purple if that helps

jaybrown

I don't hear rattling in the engine. I did a bit in my muffler but I got it welded and that was the issue there

Synthetik

I would remove the CAI. I agree with whoever told you that it could be causing a lean condition. MAP based fuel injection systems don't adapt to engine modifications very well. At least not without a tune.

Backfiring is not normal. Backfiring can be caused by a lean condition, a bad tune or a failing fuel system which will in tune cause you to lean out. If you're still under warranty. Have the dealer check it out.

Won't make a difference.

jaybrown

That means most of the people on here are running lean if they have a 3.8. I have the same set up. Cai, exhaust, superchips

DanieltheManual

Nobody upgrades injectors? ??? They are maxed out already, then add more air with a cai and you'll have a recipe for disaster when wheeling and keeping revs up ... My. 02

Synthetik

Injectors are maxed out? Where did you get that information?

I assume you hooked a scanner up to yours. What duty cycle were your injectors at?

Synthetik

Not necessarily. Things such as load and environmental factors play a role as well. However I do see quite a few threads on here about people noticing their 3.8 pinging.

Mine pings with the stock tune and 87. Dealership refuses to acknowledge it as a problem. I'm forced to run 89. It was worse when I had my K&N intake installed. I put the stock air box back in and it pings less but it's still a problem.