Good power, but misfiring!
12-13-2018, 08:58 PM
#1
Good power, but misfiring!
So I had my car tuned last week. Here’s the short mod list:
B&B Bullets
Speed Engineering 1-7/8” long tubes
K&N air filter
Powerbond UD Pulley
The car made great power, all things considered. The issue is in those little dips you see on the graphs I’ve attached. Those are misfires. Run 30 was my final one. These misfires happen mainly at higher RPMs at WOT, but can also happen at various other throttle inputs and in different rev ranges. It’ll also sputter and backfire if I’m in 6th at around 1500rpm and I floor the throttle.
My air fuel is fine too. The base map wanted it about 14.0, which is obviously high, but what was weird was that the more fuel he added the more it would miss. So it ended up around 12.8
Basically he would see the misfire, track it down and smooth that area down, and it would just pop right back up again in a different spot.
Prior to about 2 months ago, it never did any of this. It did it before the tune also, although it’s not knocking like it was before the headers and tune.
So my tuner and i are trying to get this figured out.
Our first theory is coil packs. The second is fueling, although that seems less likely given that my injectors have been cleaned and are in good shape, could be the pump though idk
any input? I sincerely hope it’s just the coil packs or something nice and simple like that, but what do y’all think?
B&B Bullets
Speed Engineering 1-7/8” long tubes
K&N air filter
Powerbond UD Pulley
The car made great power, all things considered. The issue is in those little dips you see on the graphs I’ve attached. Those are misfires. Run 30 was my final one. These misfires happen mainly at higher RPMs at WOT, but can also happen at various other throttle inputs and in different rev ranges. It’ll also sputter and backfire if I’m in 6th at around 1500rpm and I floor the throttle.
My air fuel is fine too. The base map wanted it about 14.0, which is obviously high, but what was weird was that the more fuel he added the more it would miss. So it ended up around 12.8
Basically he would see the misfire, track it down and smooth that area down, and it would just pop right back up again in a different spot.
Prior to about 2 months ago, it never did any of this. It did it before the tune also, although it’s not knocking like it was before the headers and tune.
So my tuner and i are trying to get this figured out.
Our first theory is coil packs. The second is fueling, although that seems less likely given that my injectors have been cleaned and are in good shape, could be the pump though idk
any input? I sincerely hope it’s just the coil packs or something nice and simple like that, but what do y’all think?
Last edited by DeathMetalAsian; 12-13-2018 at 10:52 PM.
12-14-2018, 11:48 AM
#3
What program is your tuner using? Are you throwing any codes?
It's either fuel or spark related most likely, if your tuner was able to tune it out. What does your vacuum look like? I'm wondering why your tuner is trying to figure it out. He should be able to see in the logs what is happening and track it to a bank, and probably cylinder(s).
In this case you can eliminate coil pack(s) by switching them to the other side and see if the problem follows (you need to be logging it to see the banks). As for fuel make sure you have a good pump and getting the 58ish psi at the rail. Make sure you don't have any air being ingested after the MAF.
What did your AFR do when the dips happened?
I'm guessing you have a mechanical failure, or vacuum leak since the issue has been there prior to the tune.
Edit: Also something you can do is pull and read your plugs for each cylinder. Check out this link.
It's either fuel or spark related most likely, if your tuner was able to tune it out. What does your vacuum look like? I'm wondering why your tuner is trying to figure it out. He should be able to see in the logs what is happening and track it to a bank, and probably cylinder(s).
In this case you can eliminate coil pack(s) by switching them to the other side and see if the problem follows (you need to be logging it to see the banks). As for fuel make sure you have a good pump and getting the 58ish psi at the rail. Make sure you don't have any air being ingested after the MAF.
What did your AFR do when the dips happened?
I'm guessing you have a mechanical failure, or vacuum leak since the issue has been there prior to the tune.
Edit: Also something you can do is pull and read your plugs for each cylinder. Check out this link.
Last edited by insertclevername; 12-14-2018 at 12:02 PM.
12-15-2018, 10:48 PM
#4
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St. Jude Donor '13-'14-'15
Just to clarify All engines at P/T should run an AFR of 14.68-1 This is called 'stoich" fueling the most efficeient raitio for a gas engine----However when you go to what they call "power enrichment" or the throttle going past aprrox 70% the AFR changes A stock tune has a rich PE of about 11.5-1 But for a D/D performance car you would want the PE AFR's to be like 12.5-12.7 -1 Now on a dedicated race car they often tune them to run on the edge of lean to make more HP --Like 12.8 to 13.0 -1
Long tube headrs are illegal in most states--reason being on LT's the front 02 bungs are moved as much as 3' aft from the stock locations This in turn makes your front 02's not to heat up correctly and your engine will run horribly RICH at P/T There is no 100% fix for this However tuning can make it closer to the stock 14.68 at P/T And then at WOT the only true way to achieve the AFR's you want is to use a Wideband 02 sensor tool and you can custom tailor your AFR's at WOT or PE to get the fuel ratio you desire----
PS many people with LT headers will install the rear 02's onto the front locations as the rears are far more sensitive than the fronts and tend to heat up better------Ideally you would want your front 02's to have an average between .400 and .500 milivolts---anything higher means the AFR is way rich---Lower means it is way lean at P/T
Also when you fueling is askew at P/T it also affects your WOT AFR as well as that % is carried over to WOT IF your fuel trims are POSITIVE
Long tube headrs are illegal in most states--reason being on LT's the front 02 bungs are moved as much as 3' aft from the stock locations This in turn makes your front 02's not to heat up correctly and your engine will run horribly RICH at P/T There is no 100% fix for this However tuning can make it closer to the stock 14.68 at P/T And then at WOT the only true way to achieve the AFR's you want is to use a Wideband 02 sensor tool and you can custom tailor your AFR's at WOT or PE to get the fuel ratio you desire----
PS many people with LT headers will install the rear 02's onto the front locations as the rears are far more sensitive than the fronts and tend to heat up better------Ideally you would want your front 02's to have an average between .400 and .500 milivolts---anything higher means the AFR is way rich---Lower means it is way lean at P/T
Also when you fueling is askew at P/T it also affects your WOT AFR as well as that % is carried over to WOT IF your fuel trims are POSITIVE