Miss on Big End

[Chuck]

So off throttle the car goes in to decel fuel cut off, so you're wide band will show max at that point, usually 18 for AFR. On throttle is where you don't ever want to see that happen. 11.5 - 11.8 on gasoline is the range. I'm diagnosing over the internet, but I'm highly confident you've got some kind of fuel issue.[/

Yes that is what is happening wide band goes 18.0 it’s like a switch turns on and a while later it switches off and runs fine that’s why it’s got me stumped not computer savvy I guess I could go ask my 5 year old grand daughter

 

[cole3986]

I had a similar problem, the plugs need to be removed and/or replaced. Under high boost, plugs will not fire if the gap is wrong or plugs have crap on them. IMO, replace the plugs with a non projected plug that has a tight gap.

I had the problem with Brisk plugs, IMO, Brisk plugs are terrible, I will never use them again.

 

[Mean Cat]

Yes that is what is happening it’s like a switch turns on and a while later it switches off and runs fine that’s why it’s got me stumped not computer savvy I guess I could go ask my 5 year old grand daughter

Make sure the injector plug connectors are all plugged in good & data logs should show if their not working all the way, & if not I would upgrade & change them all.

 

[Mean Cat]

I had a similar problem, the plugs need to be removed and/or replaced. Under high boost, plugs will not fire if the gap is wrong or plugs have crap on them. IMO, replace the plugs with a non projected plug that has a tight gap.

I had the problem with Brisk plugs, IMO, Brisk plugs are terrible, I will never use them again.

He said the plugs looked good ?... but the gap could be too far apart.

 

[cole3986]

He said the plugs looked good ?... but the gap could be too far apart.

The plugs could look great, if the gap is too big for high boost conditions (e.g. high rpm under load) engine is going to sputter and miss. The gap should be decreased as boost increases, for example, 19 PSI of boost should be gapped 0.028 inch or less. Hellcats that use nitrous should use non projected plugs (electrode doe not stick out). Just my 2 cents

 

[Mean Cat]

The plugs could look great, if the gap is too big for high boost conditions (e.g. high rpm under load) engine is going to sputter and miss. The gap should be decreased as boost increases, for example, 19 PSI of boost should be gapped 0.028 inch or less. Hellcats that use nitrous should use non projected plugs (electrode doe not stick out). Just my 2 cents

@cole3986 , regapping my plugs is something I haven't done either since I did my 2.85 pulley, 15>16 psi of boost, I haven't noticed any problem though, should I regap & to what?

 

[cole3986]

@cole3986 , regapping my plugs is something I haven't done either since I did my 2.85 pulley, 15>16 psi of boost, I haven't noticed any problem though, should I regap & to what?

Nope, leave them alone, if your cat starts missing under high load, high boost conditions then look at the plugs. It takes a lot more energy to generate the spark in a high pressure environment. Some address by using real hot coil packs but the gap is always reduced as cylinder pressures increase. The use of leaded race fuels further exacerbates the problem as the plugs get coated with lead.

 

[Mean Cat]

Nope, leave them alone, if your cat starts missing under high load, high boost conditions then look at the plugs. It takes a lot more energy to generate the spark in a high pressure environment. Some address by using real hot coil packs but the gap is always reduced as cylinder pressures increase. The use of leaded race fuels further exacerbates the problem as the plugs get coated with lead.

OK thanks, I'll leave them alone, since I have no problem so far, my tuner said they would be fine as is but wasn't sure.

 

[16GoManGoHC2]

Coil packs could be bad as well, weak spark same as plugs with a gap to big under high cylinder pressures. You have another set you can try?

 

[Chuck]

Coil packs were changed out spark plugs are new they are Brisk plugs 12S gapped at .028.
The Ecm is sensing something and going into a safe mode at high rpms with boost or no boost it doesn’t matter or what gear I’m in it’s like switching on a switch and then off again and everything is fine

 

[Mean Cat]

Coil packs were changed out spark plugs are new they are Brisk plugs 12S gapped at .028.
The Ecm is sensing something and going into a safe mode at high rpms with boost or no boost it doesn’t matter or what gear I’m in it’s like switching on a switch and then off again and everything is fine

Like many have said, I don't like the Brisk plugs but guess they are ok, besides maybe a bad pcm, I keep coming back to the injectors them selves or connections ?

 

[16GoManGoHC2]

Try stock NGK plug gapped at .026”

 

[16GoManGoHC2]

These

 

[Hpindy]

Did you clean the sensors in the intake tract? I once had a piece of something stuck in my MAP of sensor and drove me nuts for 3 months before. Im just spit balling here.

Sent from my BBF100-2 using Tapatalk

 

[Speedy!]

Guys, plug firing problems would show a rich condition in the Logs from not igniting the mix I think. His is very lean.

 

[Chuck]

I have the injectors out and getting tested pulled all sensors and looked for contaminates and check the harness.

 

[16GoManGoHC2]

Guys, plug firing problems would show a rich condition in the Logs from not igniting the mix I think. His is very lean.

After what I saw last night at the track I don’t know about this, I still think it’s plugs or coil packs. Here’s why.

I took my 84 Capri to the track last night. I use a MSD 6AL-2 ignition system, it’s rev limiter and launch control system cut spark not fuel (I run nitrous on it, cutting fuel a BIG no no!!)
I also have a in dash right where I can see it Wideband O2 display, when I used used launch control and it’s up against it cutting spark to every other cylinder randomly what did the AFR meter display?? A LEAN condition, like off the scale lean condition not rich like one would think from unburned fuel, why? Because it’s seeing a ton on unburned oxygen as well in the exhaust stream, what does an O2 sensor detect, fuel or oxygen? I can video this later and post if needed.

O, BTW, for the curious, made it to the semifinals, lost by .0568 seconds, so damn close to $250 prize
Was a BLAST though, a MUCH needed one

 

[16GoManGoHC2]

These coil packs are made by MSD for this company, I have a buddy running them along with the NGK plugs gapped at .024” and they took just took care of his miss in the big end.

 

[16GoManGoHC2]

@cole3986 , regapping my plugs is something I haven't done either since I did my 2.85 pulley, 15>16 psi of boost, I haven't noticed any problem though, should I regap & to what?

I’m at that same boost level, .028” gap is fine, I went down to .026” for some safety factor and also for flex which I’m now starting a tune for.

 

[Chuck]

Just got a email the injectors are all good have one that is right on the borderline
He told me it wasn’t my problem the miss is somewhere else
So on to the next thing replacing all the sensors
Debating about replacing ECM