s13 sr20det High RPM ignition break up

[ivantheterribl3]

this is going to be a bit long winded, so please bear with me.

It all started at East Coast Bash a couple of months ago. After one of my runs, the car started idling very poorly and nearly stalling, and my wide band gauge turned itself off. I did another couple of runs this way and it still ran beautifully off idle. Pulled very hard and smooth in the boost. it was the end of the day, so i elected to screw with it upon returning home. When i got home i discovered that the fuse for the radio was loose in its holder. Figured it was an easy fix as I have power for my wide band controller (which provides my ecu with stock narrow band signal) tapped off here. Once i made the repair i took it on a test drive. the problem changed from running poorly down low, to a consistent ignition breakup starting between 4500 and 5000 rpm and remaining constant through red line. naturally i went back to the original problem. i removed the fuse for the wideband completely and went for another spin. problem remained the same. From there, this has become a hellacious diagnostic nightmare. so on to the meat.

Engine:
S13 sr20det
garrett gt2560r
tomei 268/270 cams w/ adjustable gears
AEM 3.5 bar MAP sensor
GM IAT
Denso 550cc injectors
DSM resistor pack
AEM EMS Series 1 (30-1601) Tuned by ISP racing in beltsville, MD (Great guys. factory trained AEM tuners. fair pricing. highly recommended!!)


I have tried replacing the following parts with either new, or known good:

-spark plugs (NGK bkr7eix) gapped to .024
-coil packs
-coil pack harness
-ignitor chip
-CAS
-TPS
-Coolant temp sensor (both gauge and ecu sensors)
-CTS sub-harness
-MAP sensor
-Alternator
-EGI relay
-Ignition switch

The car runs the same with the IAT and or o2 controller unplugged

In addition to all of this, i have tried:

-Removing the engine harness, unwrapping, checking each wire individually for breaks or anything out of the ordinary, depinning all unused wires from various connectors, and replacing the wire i was using for MAP signal with shielded

-Cleaning all existing grounds

-Making a new "ground harness" going to various points in the bay and under the dash, ultimately feeding back to the battery

-messing with various settings in the ECU

-powering the coils directly from the battery (big red/blue wire that goes to the ignitor)

And im sure several more things that i am forgetting at the moment.

key on, engine off, there is a slight fluctuation in engine load (about .06 psi), coolant temp (about 2 degrees), and injector pulse (which i attribute to the fluctuation in the MAP signal). by looking at logs, i can see that it does the same thing while driving, and gets worse under boost. for what its worth, the signal noise looks significantly worse with the analog output from the wideband controller connected, but the problem feels the same in the seat of the pants. Fuel pressure is a solid 45psi. No boost leaks. Fuel is fresh 93. After everything, i feel like the problem has gotten better, but it could just be in my head....

One time while test driving/logging, there was a loud backfire. the car was not responding to throttle inputs. i took it out of gear and it stabilized to idle. put it back in gear, and it ran like it never had an issue!....for a moment. another loud backfire 2 pulls later, and its right back to the same old thing. in that log, the parameters all freeze for a couple of seconds. i have the log (and several others), and will provide those and/or my cal as well upon request

Im having trouble recalling any more information at this time, and if i were as thorough as i could be, this would be a novel. If ANYONE has ANY ideas that i havent tried, or an inquiry you may have that i havent covered, DO NOT HESITATE TO THROW IT OUT THERE!!! I am at my wits end with this piece of shit.

THANKS IN ADVANCE!!!

[Rafi Casas]

have you checked the o2 sensor? would explain bad idle and why the wideband turned itself off, might have taken a crap on you?

EDIT: if there is no change when you unplug the o2 sensor then it's probably gone bad, if it was working properly wouldn't it be all over the place with back fires and unstable idle and rpms, i'm no mechanic just something i would look at first

[ivantheterribl3]

First off, the idle stabilized after I repaired the loose fuse. Amd the problem switched to my high rpm breakup.second, I eliminated that as a possibility by turning off o2 sensor feedback in the software.

[ivantheterribl3]

Over four hundred views and nothin? Somebody has had to have seen something similar on these hateful old s1 boxes!

[ultimateirving]

A few random ideas.
I didn't see a boost leak test in your list of diagnoses.
I would also have you inspect the fender well wire harness if it's it been relocated.
Knock sensor is correctly installed and wired?
I didn't see any codes listed so I'm assuming you didn't show any.

[ivantheterribl3]

Car is tuned on an aem s1 ems. 30-1601. Runing on speed density so it wouldn't react in this manner to a boost leak. Regardless, there are none. Does not have knock control turned on.

Edit: Fender well harness is fine

[ivantheterribl3]

Last things I hadn't tried: remove resistor box and replace with brand new high impedance injectors, replace cam sensor wheel. Broke down and did those. No change in my issue. Called AEM and got an RMA #. Ecu is getting shipped to cali this afternoon

[ivantheterribl3]

Just received my ecu back from AEM today. Got a vague email from them stating that they updated it and removed the high side coil drivers, and it tested good. I plugged it in and took it for a spin. Surprise surprise. Its still fucked. I literally cannot think of anything else. I'm going to keep stewing on it and plugging away, though...

[JKTUNING]

I know this is incredibly simple, but make sure you aren't hitting boost cut (or just on the edge of it) AND if you have launch control enabled disable it.

The other thing would be fuel supply, might not be a bad idea to pull the fuel pump out and look it over. I run into this issue just about on a weekly basis while tuning cars on the dyno, it is a lot easier to diagnose when you have it in a test environment and can log or monitor fuel pressure throughout the pull.

Depending on how much boost you are running, maybe try tightening the gap up on the plugs .. even though they are already pretty low.

[ivantheterribl3]

Ray with vvl sr actually recommended I speak to you lol. I've found another walbro i plan on trying. Launch control is off and it has ignition cut set at 7 and fuel at 10. Since the original post I gapped the plugs down to .020 with no change. I'm going to remove the valve cover and Inspect the valvetrain for the 4th time after work. Based on my logs I am convinced I am fighting an electrical gremlin, but I could be wrong. MBC set at 13lbs. Havent touched it since it got tuned. Also I have removed the resistor pack and 550s and replaced with a brand new set of high impedance rc 750s, and re scaled my fuel map accordingly

[steve shadows]

I would check the fuel pump out. Have seen them go and the break up just gets worse and worse. Sometimes it's hard to see it on AFR it's just a very quick spike to lean as the pump is shitting out.

Also if you want you can email me over the AEM map I can check out the settings for you and re-map it remotely for better timing and the fuel tables for $45 pp.

Start with fuel hardware first though. That's where I would begin.

[ivantheterribl3]

Thanks steve that's actually going to happen tonight. Last night I tried hard wiring the pump direct to battery and it made no difference but my friend has an extra pump I can try. Its one of the only thngs I haven'tareplaced thus far

[steve shadows]

Yeah I'll do a run through of the map for you and rebuild it for 45$ if you want. I usually charge 85 but I can run through it and at least get you a timing map in there that is race ready and check all the fuel settings out so you know you're all set.

Let me know how it goes either way!

My email is [email protected]

Thanks

[inopsey]

Yeah I'll do a run through of the map for you and rebuild it for 45$ if you want. I usually charge 85 but I can run through it and at least get you a timing map in there that is race ready and check all the fuel settings out so you know you're all set.

Let me know how it goes either way!

My email is [email protected]

Thanks

so nice of you to charge $$ for helping out in the tech section

[tasnailman]

Hi mate. Just wondering how you went with your fuel pump? Did it fix the issue. Yes I realize the post is 2 years old but???

[ivantheterribl3]

Hey man. Long story short the fuel pump ended up being a bit weak but it wasnt the cause of the break up. The break up was caused by a bad wire in the harness. The one from the ecu to the cylinder 1 channel on the ignitor chip. I figured it out by putting it on a dyno amd unplugging injectors during a pull. While the break up felt random because it was at sich high rpm, it turns out it was just #1.

[quickdiversion]

I have a few question first about your setup.

-You are running a t25 series turbo,regardless the make and model with rather large cams, how come? They are over kill for your turbo and more likely your problem. They are flowing so much by 4500-5000 rpm that you are exceeding the limits of that turbine, pretty much just generating heat at that range. I am running tomei 270/270 on my hx35 setup.

-You are running a .25 spark plug gap, this is undersized for the stock gap which is.28. Where you getting blow out and had to reduce it?

-How much boost are you running? I am going to assume you are at full boost when you are having ignition break up?

I have 2 options for you:
You can upgrade your ignition, like I do because I was getting spark blow out and ignition break up. I swapped over to LS2, which is very easy. I have all the settings for the power fc I can give you. Your guy can translate them to your AEM. But wiring and install is cake. Nismotronic picks them up automatically. I think AEM even has a selection for them.

Second option, which I feel your problem is. Get smaller cams, run 256 in and 260 out or 260/260. I ran those on my 2871r setup and the car flew with no ignition problems. I have a feeling your are flowing to much air for that tiny turbo with those cams and you are exceeding its limits at that rpm range.


Just another angle to look at it for you.