[ZL1REDHOT]

I have a stock 2018 ZL1 vert. except it has a Roto-fab cai on it. Its not the big gulp. My exhaust smells very strong or rich. No warning lights on, runs great. Do all ZL1's do this with Roto-fab's installed or is there a leak after the MAF sensor. Gas mileage sucks also. Thinking about taking it off until i'm ready to do mods. Thank you in advance!

[RobZL1]

Do you have experience with it before the roto-fab or did you buy it that way? Are the secondary cats removed? The secondary cats do a lot to clean up idle exhaust smell.

[ZL1REDHOT]

Bought it this way. Stock exhaust.

[wakespeak]

I went through this. My catalytic converters are somewhat done from track use so the car has a bit more exhaust smell. Having said that it had more of a raw gas smell recently.

Potential causes:
1) Evap solenoid stuck open. Easy to replace. Replaced
2) MAF easy to clean or replace. Cleaned.
3) Misfires. Car won't throw a code unless really bad. Replaced plugs, wires, coils.
4) High pressure fuel pump leaking, leaking injector(s). Car held fuel pressure at shutdown at an expected bleed off rate.

Was #3. Apparently the coils last about 60k under normal use, a lot sooner with track use and high heat.

[KingLT1]

Check all the clamps/connections from the throttle body to the rotofab. A leak will throw off the calibration, and the ECU will add fuel from a false lean condition. If that is not it, then it maybe a fuel injector. I would try to get a scanner hooked up and check the fuel trims.

[bishopts]

Also low coolant temps from cold starts and short trips will run rich.

[KingLT1]

yes, but these cars typically don't smell rich enough on cold start that someone would start a thread about the exhaust smelling strong. Between the DI, 4 cats, and cat warmup mode, they normally have very little fuel smell.

[LT4Greg]

It might have a tune on the engine if he bought the car with the RotoFab installed by a previous owner.

[KingLT1]

Op said non big gulp and those do not normally require a tune. But yes, I agree anything is possible. That is why the only real way to diagnose anything is via datalogging.

[RobZL1]

I still think he should just stick his head on the ground and see if he still has secondary cats. In my experience, without those on the earlier cars it smells a little at idle. I know he says stock exhaust, but perhaps someone cut out the secondaries. Mine came that way when I bought it.

[ZLRob]

Originally Posted by RobZL1

I still think he should just stick his head on the ground and see if he still has secondary cats. In my experience, without those on the earlier cars it smells a little at idle. I know he says stock exhaust, but perhaps someone cut out the secondaries. Mine came that way when I bought it.

Mine came that way too when I bought it. It sort of sucks, but since switching to ethanol I don't mind it, especially because it doesn't smell at all after it's been fully warmed up at idle.

[ZL1REDHOT]

Thanks KingLT1. It was the connections (clamps). They were all loose. Tightened them up and the smell is gone. Even started it in my garage. Just normal exhaust smell. Thanks everyone.

[RobZL1]

Awesome! Easy fixes are the best fixes.

[KingLT1]

Originally Posted by ZL1REDHOT

Thanks KingLT1. It was the connections (clamps). They were all loose. Tightened them up and the smell is gone. Even started it in my garage. Just normal exhaust smell. Thanks everyone.