dckotwicki

I am noticing an odd behavior that I would describe as engine loping during moderate acceleration. If you apply a bit more "foot" to the pedal, it seems to clear itself and get on with things.

Could it be that the engine is in too high a gear and a bit more accelerator forces a downshift?

K1600GT

Oh boy. I have same issue and have been fighting with GM for 5 months now. GM describes it as normal and refers to it as "Fish Bite". Feels like a miss fire when slowly accelerating in 6,7,8th gear from 1200 rpm to about 2600rpm. Theye gave me a bulletin on it. I refuse to accept this as normal or acceptable. Mine will do it in any gear at any rpm, it really sucks. Had torque converter replaced and now it is worse. I filed with BBB and am now on the final repair attempt step. GM is bringing some guys in Thursday to look at it. Dealer agrees the behavior is not acceptable for this car. We'll see what happens Thursday.

Pro Street

I have had my Z for five weeks and it has done this from day one. My car only has 1060 miles and I was hoping it would get better after more miles. I have not talked to my dealers.
Let us know how it goes with your car.

BELVIN20

Like to hear what the excuse is, my 2016 Z has the "Fish Bite" since day one, I now have 8k miles on it & no change. I believe it is plugs, but no way to get dealer to change plugs without a CEL. But it seems I read a post a while back where the dealer did change plugs & fixed the problem.

K1600GT

I was going to change mine but looks like a real PIA.

gve

I think it is a lean condition under load and is made worse by lower octane. If I use 91 octane it is really noticeable when I use 93 it is better. We just got back from a trip in Canada where they sell 94 octane and it was completely gone and the engine never ran so good.

K1600GT

that is great to hear. I'll try some higher octane fuel and see what happens with mine. They said the fuel trim was a little high but I don't know how to interpret that; rich or lean. Mine feels like a lean miss.

gve

That's exactly what mine felt like, I wish we could
94 octane at the pumps like Canada

davepl

I've never had it (or not noticed it if I do have it), but wouldn't OBD2 catch an actual misfire, or is it harder for it to do it under acceleration as opposed to steady-state idle/cruise I wonder?

Or is it not really misfiring at all, and just feels like it?

gve

I think it still is firing but with the load and at the lower rpms it needs the higher octane to overcome the lean firing.

gve

Make sure you don't try leaded race gas it will screw up your cats and oxygen sensors.

Jared@anmg.net

I was having similar issues and started adding Torco to the 91 octane gas. Engine runs much better now.

gve

Here is a site I use to find 93 octane, it's listed by people reporting when they find a station with 93. I also reported to them when I went to a station and they no longer had 93, so the more everyone reports the more accurate it is.

https://find93.com/

K1600GT

Would a tune from an aftermarket speed shop help the issue? Maybe General Motors will give me permission to get a tune that allows the car to perform properly. Also keep the warranty.

K1600GT

My understanding is that lower octane is more explosive. Higher octane is less explosive or less flammable. so wouldn't a lean mixture of something more explosive have a better better chance of igniting then the same mixture of less explosive gas mixture

K1600GT

Can I run 100 low lead or will that hurt the cats also?

AllFlash

Very interesting thread. I live in Canada and just returned from a very long trip though the States and out East where 91 is as good as it gets. I use nothing but Petrocan Ultra 94 and remember a number of times during my trip thinking something was off... As much as I did attribute it to bad gas initially, I never considered the Octane rating overall until I hit my second fill of 94 now that I am back... Car is like a rocket once again and feels very... hmm ... quick in the jump even when cruising....no more chug.

383vett

For real?

K1600GT

Well maybe not. They won't even let people add cooling mods to help protect the engine. What the hell was I thinking.

383vett

Wishful thinking never hurt.