yosip1115

I am losing my mind troubleshooting why my car has been knocking under high load conditions. It happened while driving, and I have been on this for two weeks now delving into details with no luck.

I can't take this twin turbo car to a shop, you guys know how poorly that turns out. The issue seems to be minor, but it doesn't take much to throw one of these cars out of whack.

I can get into the details if someone is willing to help me out here who has been around FI Z's running uprev to explain what happened, what I have done thus far, and what the car is doing.

Thanks!

iideadeyeii

iTrader: (6)

If AFR is correct(and you are using highest octane available) then you need to retard timing

yosip1115

Hey deadeye, I don't think so, because the tune is fine, and it happened while driving.

Fuel correction is not fine under all conditions, but I have smoke tested for pre and post maf leaks. Something is up, I wish it were as simple as a popped coupling but that is step 1 for troubleshooting when correction values are off

BluestreamDE

Shooting from the hip here but...


What are your AFRs looking like under WOT?


How much timing are you normally seeing in the upper RPM ranges under full throttle?


How do your spark plugs look? (If they are chalky looking you are running a bit lean, if its wet with carbon buildup its running rich, which in your case I doubt you are knocking under a rich condition)


How is your fuel pressure? is your FPR raising pressure 1:1 and raising with boost increasing?


EDIT: "IF" the tune is fine, so you say, its got to be something mechanical that posing the issues. I would check fuel system and ignition components first.

yosip1115

Lol yes we will be shooting from the hip until I get my past few weeks of troubleshooting out here in writing. Thank you guys for helping out though. This has been a big bummer right at the beginning of the season.

Regarding timing let me dig up some logs from before I had issues to get that info. I have not been logging timing lately but should have been and can tonight. I figured the knocking would throw it all over the place since (I think) it would retard timing when the knock sensor is tripped.

Spark plugs looked consistent across the board, but I definitely see lean spots in my logs (and rich ones too.....). Corrections are sort of all over the place, hard to draw a conclusion. Fuel system makes more and more sense... But don't let that bias you because I have seen clear evidence that it was bank two, that it was a global thing, and that it was bank one all in the past few weeks. Right now at idle B1 correction values fluctuate much more than b2, but see edit below.

Fuel pressure while driving is something that I do need to check because I have checked and replaced a lot of things besides that. It is OK at idle, but that would make sense if something let go in my fuel sending unit that my pump can make up for until the engine demands a lot of fuel. I will look at this after work tonight with a camera or something lol.

Regarding AFR's in WOT, I can tell the engine would let go if I floored it right now. I am registering a serious knock when the turbos spool up. I have plenty of partial throttle logs that I will attach.

It's pretty crazy, but I found that a wastegate valve had seperated from the valve stem (evidently this is common for the tial FG38's) so I replaced the bad one after swapping the spring and inspected the other one (silicon diaphragm was good, smooth motion, valve in one piece). Figured that was that and went for a spin, only to find that it was not the root cause.

I dug a little further and found my B2 turbo bearings were on the way out. Plenty of shaft play axial and radial and I actually only heard one turbo wind down after throttle blips. I was convinced that the turbine was hanging up, (coincidentally b2 to ran 1:1 leaner than B1 when boost came in as noted while logging), accompanied by the knock. Easy fix right? Replaced the turbo, smoke tested again, and went out for a spin to find that it STILL KNOCKS UNDER LOAD

That is where I am at now. Two + weeks and $1500+ later. I can hear both turbos wind down now after throttle blips, so at least that is over with. No more antilag for me.


I have a bunch of logs as the car sits right now from last night. Things have been changing in random ways in logs (mainly fuel correction values) as I have been troubleshooting so it has been hard to draw a conclusion.

That was super windy/unorganized so sorry about that. Let me get those logs attached and see if I can find some older ones that have timing

Edit: yes, I am confident in the tune. Rt tuning is top notch. I wouldn't be able to make 470WHP without a tune that is spot on so I agree that it is something mechanical, or a sensor. Since it runs good until load comes and there are no misfire codes I think we can rule out ignition? That leaves fuel. On the other hand b2 seems fine now at idle and fuel would be a global thing :/ but looking at the 1-4th log it does seem to be struggling with both banks either pulling or adding fuel to them both when it is making a correction.

Let me know what you'd like me to log and I'll make it happen tonight while I check the fuel pressure when driving too.

yosip1115

Fuel pressure checked out just fine, nothing below 52 psi and raises as it should

TT03Z

Is the car running fine in boost or are u having a misfire issue when boost comes in. You will typically see some knock when power is coming in. You don't want knock with full boost is where the problems come in. How much boost is present when u see the knock?

yosip1115

[QUOTE=TT03Z;10955049]Is the car running fine in boost or are u having a misfire issue when boost comes in. You will typically see some knock when power is coming in. You don't want knock with full boost is where the problems come in. How much boost is present when u see the knock?[/QU



I agree that there should be no knock. I am unsure that it would be normal to see any knock even with power coming in, our ECu's would pull timing when they sense knock, right? I have never seen knock before in any circumstance until this happened.

Feels like a misfire in boost but I get no misfire code. Problem occurs strictly in boost. AFR corrections aren't exactly perfect in vacuum like they usually are either, so I almost think there is a cam or crank sensor on the way out since I have checked everything else

Hard for me to say right now how much boost is present when it begins hitting but it is at least a few pounds (over 5), so I have to let off obviously. It is much worse in higher gears than 1-2. So it is load dependent.
My innovate boost gage ties into uprev and outputs a funky unit that I am not able to make much sense of... 23 inhg is a .28, 26 inhg is a .23, it takes a few pounds of boost to get it to be more than 1.0 in the log. Doesn't make sense for that decimal to be in bars absolute or relative, so that is a bit confusing.

There is a log attached including this weird innovate data output if you have a second to open it up. See the 1234 attachment in my post earlier. There are a few others too at idle and what not.

I reached out to my tuner and I need to take more logs tonight for him. I threw in the towel and inquired about some remote troubleshooting support. Since I have been going there with a few different FI setups they were willing to help at this busy time of the year for $200. Hopefully he spots something in the data that the ECU hasn't picked up on yet

Boost
A/F Correction Bank 1 short/long
A/F Correction Bank 2 short/long
A/F Ratio B1
A/F Ratio B2
Acc Ped Pos 1
B-Fuel Schedule
Calculated Load Value
Coolant Temp
Engine RPM
IGN Timing
INJ Pulse B1
INJ Pulse B2
Intake Cam Timing B1
Intake Cam Timing B2
Mass Air Flow B1(Volts NOT G/S)
Mass air Flow B2 (Volts NOT G/S)
Throttle Position 1

yosip1115

It was a freakin coil pack going bad, never tripped a code but we ruled everything else out but spark... Glad it is back!

TT03Z

Man I'm suddenly having the same issue haha. Only breaks up in boost. Changed plugs a/f is good I'm gonna swap coil packs n give it another shot. Only problem is I replaced the whole set with brand new ones about 2k ago soooo we'll see.

yosip1115

How much power are you making, and what is your Gap set to?

TT03Z

Car made 575/602 on a mustang Dyno at 20psi. I'm running the LFR7AIX NGK iridium plugs at .022. currently running 22.5 psi with a few more mods since Dyno time. Misfire just started all of a sudden so I changed plugs hoping that was it but it didn't change. I have an extra set of coils I'm going to swap out and see if that fixes it today. If that doesn't fix it it's probably an injector and time to switch over to some 2000cc's and E85.

yosip1115

but you said AFR's were fine, I hope it isn't an injector ha

TT03Z

It's definitely not a coil issue. I changed them 1 bank at a time and it didn't clear up. I'm gonna do a compression check quick before I pull injectors. Fingers crossed that's not the issue.

yosip1115

Post results

TT03Z

That moment you realize plugs aren't fine...went to do a compression test and this one free spun in the hole. Houston we have a problem....this should be fun

yosip1115

Jeez that wasn't noticeable at idle/partial throt? I had that happen to a friend of mine, loose plug in #2 on a STOCK z, and it ran like Doo Doo.

What do you think caused that? Installation negligence? Are more than 1 like that?

BluestreamDE

I've personally never seen this happen before, holy crap man! Was it Overtorqued?

How are you going to screw the rest of it out?

yosip1115

I've read about the iridium plugs doing crazy things like this, I stick with laser platinum 1 step colder. At that hp level though... No clue... 2 steps colder laser platinum?

TT03Z

Sad part is I just put these in to fix a misfire.... I always put them in and tighten them the same way. I screw them in hand tight then feel the washer crush and go another 1/8th of a turn