Unknown Misfire 2013 ZL1 408 LSA

[drewbo]

Hello all,

My ZL1 appears to misfire / cut fuel consistently, but randomly.

Driving around, throttle at about 30-40%, car will misfire in the range of 2.5k-3k RPMS in 2nd or 3rd gear, AFR spikes to about 20.0, if I hold TPS at the same position, it will continue to misfire if I move it a tiny bit, it goes away, also happens right when letting off clutch and going on gas if throttle is at 30-40%. O2's reading flat, happens at the same RPM in 6th gear too. Fuel pressure seems fine, cannot figure out for the life of me what it is. Been chasing this down for 2 years. Any help is appreciated. See the attached tune file & logs.

Total specs are as follows:
Texas Speed 408
Ported LSA Blower, 2.55/9.06
"In Tank Walbro 450", Keene Bell BAP, SMG Aux Pump, other parts of fuel system are stock
FIC 1300s
Tuned by me

zl1 misfire.hpl
misfire 6th gear 1215.hpl
zl1 lots of misfires.hpl

"zl1misfire" see 50 seconds in
"misfire 6th gear 1215" see 12 min 05 seconds in
"zl1 lots of misfires" see 8 min 47 seconds in

current tune v2 zl1.hpt

See attached tune file, happened while tuned on either MAF or SD

[GHuggins]

Have you checked compression? I haven't looked at anything. Just asking. It doesn't take much of a cam to make the valves kiss on these even with some decent cut pistons, so one good rev to 7000 and anything's possible. AND before you ask, you won't notice it all the time when they do, just under full power or heavier engine loads so if it's only missing at lighter loads then it's most likely a lean issue. If compression checks out good another problem I found with the lsa blowers is when they are spun a lot they feed more air to certain cylinders causing lean issues to those cylinders. IF you know which cylinders are missing and you have an E67 ecm you can try using individual cylinder fueling to add fuel to those cylinders. Can even be plugs or wires if running headers or injection timing if pulse widths are small enough in your trouble areas. Just spit balling things to check.

[drewbo]

Hi Greg, thanks for your reply.

I have not checked compression, but, this same issue was happening when I had my SBE 6.2 LSA in there, so I do not think that it is a motor problem. I do not believe that my LSA is spun too much, but it also does not happen when I am in boost. Do not believe it is plugs or wires, because they have all been changed recently. In the VE table I added 20% fuel to the cells where/when the misfire happens... I believe (not 100% sure, could just be luck) that it fixes it temporarily, but eventually the issue comes back.

[GHuggins]

Looks like it's just super lean in the lots of misses log. Have you checked fuel pressure? I know you have new fuel components, but lots of new parts go bad. Your at nearly 0 mv on your O2's and at full boost where it's supposed to be sputtering.

[drewbo]

I wasn't logging fuel pressure on that log specifically, on the other log(s?) I was. I don't really see any major dips in fuel pressure, WOT is fine, no issues, only this specific part.

[Alex14SS]

The fact that adding fuel seems to solve it temporarily is interesting. Have you considered that it might be an issue with the fuel trim learning? Sometimes the ECU can get ‘stuck’ on learned values that don’t play well anymore, especially after big mods. Could be the injectors. Even though they’re new FIC 1300s, they can sometimes have issues like clogging or poor spray patterns that only show under certain conditions. It might not hurt to have them flow tested. Might be a long shot, but check the fuel pump voltage supply, especially if you’re using a BAP. Voltage drops can cause weird issues, and they don’t always show up as pressure drops.

[edcmat-l1]

It actually looks like there may be more than one problem.

Most of the time the O2s look way too hashy like you probably have a lot of secondary ignition misfires going on. There's only a couple places where they clean up and look normal. What plugs and plug gap are in the vehicle? It could also be plug wires not snapped on fully to either the coils or plugs. It a very common issue especially with DIY guys. No offense meant. Also, MSD plug wires are the worst. If they're MSDs I'd recommend replacing them with good ol' AC Delco wires.

Second thing is, it clearly ran out of fuel on a couple pulls. To me, that looks like a separate problem completely.

No fuel.jpg

[drewbo]

The fact that adding fuel seems to solve it temporarily is interesting. Have you considered that it might be an issue with the fuel trim learning? Sometimes the ECU can get ‘stuck’ on learned values that don’t play well anymore, especially after big mods. Could be the injectors. Even though they’re new FIC 1300s, they can sometimes have issues like clogging or poor spray patterns that only show under certain conditions. It might not hurt to have them flow tested. Might be a long shot, but check the fuel pump voltage supply, especially if you’re using a BAP. Voltage drops can cause weird issues, and they don’t always show up as pressure drops.

The BAP was something in the back of my mind but I was always thinking I was crazy... the BAP should be activating at 3psi, (if if installed wrong, 0 psi), the misfire always seems to happen at just around that amount of boost. Definately something to look into. Can't be injectors, same thing happened with my ID 1050's.

[drewbo]

It actually looks like there may be more than one problem.

Most of the time the O2s look way too hashy like you probably have a lot of secondary ignition misfires going on. There's only a couple places where they clean up and look normal. What plugs and plug gap are in the vehicle? It could also be plug wires not snapped on fully to either the coils or plugs. It a very common issue especially with DIY guys. No offense meant. Also, MSD plug wires are the worst. If they're MSDs I'd recommend replacing them with good ol' AC Delco wires.

Second thing is, it clearly ran out of fuel on a couple pulls. To me, that looks like a separate problem completely.

No fuel.jpg

TR7IX's @ Stock Gap, all plug wires are on & they are Taylor Spark plug wires. I see what you're saying on the screenshot with the No Fuel... but my wideband says otherwise and the car does not cut out during the pull, only during those specific portions like I mentioned.

edit: car has been ran on 93 for all of this, have had no blowout issues

[Alvin]

This is lean as while you are in low boost. Several times I saw pretty decent amount of boost while the narrowbands report higher than 14.7 and several times still looked like it wasn't in PE.

I didn't see a wideband on any logs. I must have missed it.

The fuel pressure variation is coming from the AUX pump. Those kits are garbage. I'm sorry to say. They are especially bad on manual cars. I refuse to work on cars with them anymore in our shop.

The issue is the aux pump comes on.. fuel pressure spikes high. (note a lot of injectors stop operating around 85-90 psi) so you get injector misfires that way. The FPCM rolls back the main pump with short and long term fuel pump trims, then when the aux pump shuts off the pressure isn't there because the FPCM saw it high moments before. So you get this 90 psi to 35psi variation while rowing the gears.


So..

1. Make sure you get into PE with any boost. If its still lean in those spots, well that is just tuning 101. Enrich the maf or VE in that spot.
2. Be conscious of that fuel pressure swing and realize it is going to cause driveablity issues on its on.


I don't see P2V issues being a issue here. Any built motor is going to have pretty significant valve reliefs. It's next to impossible to find aftermarket piston without valve reliefs.

attached is a image of your fuel pressure spikes/Swings. You can log fuel pump trims from the FPCM

Capture.JPG

[drewbo]

This is lean as while you are in low boost. Several times I saw pretty decent amount of boost while the narrowbands report higher than 14.7 and several times still looked like it wasn't in PE.

I didn't see a wideband on any logs. I must have missed it.

The fuel pressure variation is coming from the AUX pump. Those kits are garbage. I'm sorry to say. They are especially bad on manual cars. I refuse to work on cars with them anymore in our shop.

The issue is the aux pump comes on.. fuel pressure spikes high. (note a lot of injectors stop operating around 85-90 psi) so you get injector misfires that way. The FPCM rolls back the main pump with short and long term fuel pump trims, then when the aux pump shuts off the pressure isn't there because the FPCM saw it high moments before. So you get this 90 psi to 35psi variation while rowing the gears.


So..

1. Make sure you get into PE with any boost. If its still lean in those spots, well that is just tuning 101. Enrich the maf or VE in that spot.
2. Be conscious of that fuel pressure swing and realize it is going to cause driveablity issues on its on.


I don't see P2V issues being a issue here. Any built motor is going to have pretty significant valve reliefs. It's next to impossible to find aftermarket piston without valve reliefs.

attached is a image of your fuel pressure spikes/Swings. You can log fuel pump trims from the FPCM

Capture.JPG

Hey Alvin, thanks for the input

I didn't even notice that. Upon further research, this fuel cut @ RPM seems to be a very common thing on these 5th gens, CTS V's, and SS's. See the link below.

https://forum.hptuners.com/showthrea...rpms-2014-ctsv

Unfortunately no one on the thread has been able to find a real solution to this, and apparently, the boost-a-pump causes that fuel swing that you noted above. For now, I'm going to remove the BAP & go from there. Hopefully my new fuel system fixes this issue.

Thank you!

[sgod1100]

Hey Alvin, thanks for the input

I didn't even notice that. Upon further research, this fuel cut @ RPM seems to be a very common thing on these 5th gens, CTS V's, and SS's. See the link below.

https://forum.hptuners.com/showthrea...rpms-2014-ctsv

Unfortunately no one on the thread has been able to find a real solution to this, and apparently, the boost-a-pump causes that fuel swing that you noted above. For now, I'm going to remove the BAP & go from there. Hopefully my new fuel system fixes this issue.

Thank you!

What you are experiencing is a little bit different than what I am experiencing. The fuel pressure stays relatively stable (jumps around a little bit at that 2600 rpm), but my car has never got so lean that it was spit and spuddering at that rpm

[gtstorey]

This is lean as while you are in low boost. Several times I saw pretty decent amount of boost while the narrowbands report higher than 14.7 and several times still looked like it wasn't in PE.

I didn't see a wideband on any logs. I must have missed it.

The fuel pressure variation is coming from the AUX pump. Those kits are garbage. I'm sorry to say. They are especially bad on manual cars. I refuse to work on cars with them anymore in our shop.

The issue is the aux pump comes on.. fuel pressure spikes high. (note a lot of injectors stop operating around 85-90 psi) so you get injector misfires that way. The FPCM rolls back the main pump with short and long term fuel pump trims, then when the aux pump shuts off the pressure isn't there because the FPCM saw it high moments before. So you get this 90 psi to 35psi variation while rowing the gears.


So..

1. Make sure you get into PE with any boost. If its still lean in those spots, well that is just tuning 101. Enrich the maf or VE in that spot.
2. Be conscious of that fuel pressure swing and realize it is going to cause driveablity issues on its on.


I don't see P2V issues being a issue here. Any built motor is going to have pretty significant valve reliefs. It's next to impossible to find aftermarket piston without valve reliefs.

attached is a image of your fuel pressure spikes/Swings. You can log fuel pump trims from the FPCM

Capture.JPG

Hey Alvin, thanks for the input

I didn't even notice that. Upon further research, this fuel cut @ RPM seems to be a very common thing on these 5th gens, CTS V's, and SS's. See the link below.

https://forum.hptuners.com/showthrea...rpms-2014-ctsv

Unfortunately no one on the thread has been able to find a real solution to this, and apparently, the boost-a-pump causes that fuel swing that you noted above. For now, I'm going to remove the BAP & go from there. Hopefully my new fuel system fixes this issue.

Thank you!

I think Alvin has a Problem more with the Aux. Pumps than the BAP but I could be wrong.

[drewbo]

Tonight I'm going to pull the aux pump fuse, test it, if it continues, remove the BAP and see results.

Thanks for your input. Will update.

[Alvin]

I won't use a aux pump exactly for the reason I described above.

No problems with BAPs.

[GHuggins]

I agree with Alvin 100% on the aux's on the gen 4's. I won't tune one running one unless it's got a full return fuel system. I've even had guys get pissed about that, go to someone who would tune them then see where they blew their motors a few months afterwards. Last thing you want are injectors struggling under boost. There are some companies that claim their injectors will open under high pressure, but even then I don't trust it.

You'll need to re-tune your fuel models as pointed out after the items are removed. That thing is way too lean BAP's aren't bad as long as you're not relying on one to make your fuel supply.

[drewbo]

I pulled the fuse for the aux pump, the problem is still occuring the same way. I will post a log later on. Tomorrow I'm going to take out the BAP and see what happens.

[pannetron]

Maybe use just a CTS-V2 pump module with DeatschWerks 300C pumps?

[drewbo]

Maybe use just a CTS-V2 pump module with DeatschWerks 300C pumps?

Probably going to go with a Chris 1313 or Fore double pump system

[drewbo]

Update,

Boost a pump, aux pump, both unplugged. Fuel pressure no longer dropping, misfire is still happening. See the attached log.

ZL1 MISFIRE.hpl

See around 35 seconds. Can't figure this out for the life of me, any input is appreciated.