Snyperifle

April 14th, I installed the new shorty headers from an offbrand of DNA Motorsports I believe (they have a stamp with "Godspeed" or "Godsnow" on it, I forget the name. Anyways the welds looked pretty decent and the fitment was pretty good on the car. Only had to bend the dipstick a little to fit the headers. I have my O2 sensors on 90 degree extenders, but I still do get a CEL for cat efficiency after a while. I ran the car like that for 2 days. I lost a lot of power, which I figured was because I'm running an exhaust cutout. So the catless headers with the open cutout probably causing too much back pressure loss. I closed my cutout and the car ran really nice and strong. My car is just running catless headers > resonator delete > stock mufflers now.

Later that day, I got a misfire in cylinders 3 and 4. Not exactly sure why, but I decided to change out all the spark plugs. Six brand new spark plugs later, the car ran fine. A couple days and 70-80 miles later, misfire in cylinder 1. I cleared the code. Drove about 20 miles, misfire again. Pulled the codes

C1201 - ABS, Malfunction in engine control system
C1249 - ABS, Something about stop light switch circuit open (no idea what either means)
P0420
P0430 - these 2 are cause I have catless headers
P0300 - random misfire detected. (Later turned out to be cylinders 2 and 3)

Me and my buddies who installed the headers have checked at least 5 times all the wiring that we unplugged when installing the headers. Nothing seems to be out of place. We even went back and replugged everything to be sure. We checked all the ignition coils multiple times (swapping them around to see if the code follows). Ignition coils seem to check out.

So after all this, we figure it may be the Carbon build-up causing the misfires. I got some Mopar Combustion Chamber cleaner and did a top end cleaning. Smoke in the exhaust and some really funky smells later, the car was running really strong. But of course a while later, misfire again.

At this time, I posted my issue on my Instagram and someone (Ryan Thach) messaged me saying he had the same issues. His car got approved to do the carbon build up CSP but the issue persisted afterwards. Turned out to be his alternator that was causing it. I thought about how my car would ONLY misfire when I was at a stop (low rpms), never when it was at the higher rpms. I took my car to Autozone to get my alternator checked out and it failed the voltage regulation test. It made sense to me that if the alternator was failing, it wasn't providing enough power to the ignition coils. And since a alternator starting to go would make less power, at low rpms it may not be providing enough to run the ignition coils.

Anyways the next day my car actually shut off while I was driving. I managed to start the car and keep it on by keeping the revs up, and manage to crawl my way home on what felt like only 2 cylinders.

Today I had my alternator replaced with an AC Delco reman. My old alternator pulley did not want to turn. It had to be spun really hard to even get it to move. The new alternator's pulley was really smooth and easy to spin. So got the new one put in.
Didn't even make it down the street, misfire in cylinder 1. I cleared the code, ran down the street again, misfire in cylinder 1 and 3. Cleared the code again, misfire in cylinder 4. Cleared the code, then a new code popped up

P0354 - Ign Coil D Primary/Secondary Ckt

The car is only acting up now when it's in the upper RPMs (between 5-6k, not at idle anymore)

Had a couple friends check my ignition coils again and they all said they seemed to be working fine. Even went ahead and checked all 6, all seem to be working fine. Checked the wires again and they all seem to be in working order and in the right place.

At one point, I had cylinder 4 misfire and there was a knocking sound coming from the cylinder. It was pretty apparent and could be heard from inside the car with windows closed. For some reason the sound slowly faded away and now cannot be heard at all.

So far I've replaced all the spark plugs, changed out an alternator and did a top end cleaning. I'm still getting misfires all over the place. I've had misfires in cylinder 1, 2, 3, 4, 5 all on separate occasions, had my car die on me while I was driving, codes popping up for my brake light switch and ignition coils. I don't really have anymore straws to grasp lol. What I don't understand is that when my car is running well, it runs really strong. Does not feel sluggish at all. It will just randomly misfire.

The consistent things are, when I restart my car, the CEL and misfire go away. It only misfires in a certain situation (at idle before alternator swap, now between 5-6k rpm after the new alternator) and that the misfires seem to jump all over the place, not just sticking to one cylinder.

This all happened after the header install. Actually more accurately it happened after I installed the headers and closed my exhaust cutout/dump. I dunno how headers could cause something like this, even though it's been checked for leaks. I don't blame the headers at all, I feel like some wiring got messed up... or maybe carbon build-up decided to manifest itself up my a** really hard all of a sudden

At the moment, I can drive my car no problem as long as I keep the revs low. I CAN accelerate hard, but after a few pulls I get a misfire again, in a random cylinder

Have an appointment with the dealership next Friday to see what they have to say...
But I'm open to any thoughts/ideas beforehand...

*Edit my car is a 2008 IS250 at almost 88k miles

xvector

dude, something similar happened to me the other day after changing my tranny oil and installing a carbon hood. i had a whole bunch of codes including the ones above you mentioned.

i cleared them and after a while got them again... this drove me nuts for two/three days... i changed the plugs, changed oil, check for faulty coils and nothing.... averything dissapeared after i filled up the tank with gasoline (it was low on fuel but not ran empty, dunno why.... but this was my fix)

i know... crazy!

just for your info... this were some of the codes i had:

once time---
P2800 - powertrain
P2700 - Powertrain
P3000 - Body
P0900 - Powertrain

another time
B0124 - Body
P0080 - Powertrain
B01Be - Body
P2300 - Powertrain
P2400 - Powertrain
B0081 - Body
B01c2 - Body
B01C5 - Body

a diferent time...
P2300 - Powertrain
B0081 - Body
P2100 - Throtle circuit
C3524 - Chasis
P0080 - VVTI circuit
B01b6 - powertrain
P2200 - NOx sensor circuit

another time:
p0172 - system too rich
p0175 - sys too rich
C2C1D - Chasis
C0080 - Chasis
B01e2 - Body
P1d40 - powertrain


and the story goes on and on....

im telling you car went crazy!!!!

well, after the gas part... everything went away and been fine from there on.

chk your fuel... who knows if the same is happening to you

Snyperifle

wtf thanks for the tip. I have been on teh same tank of gas since this all started, and I filled up around 20 minutes before the first misfire... I dunno if that's just a coincidence but I'll check

mikellucci

iTrader: (56)

Guys those are very odd and random codes outside of the apparent misfires that are actually occurring. Have you checked to make sure no wiring has been burned or is exposed to excessive heat or moisture? Is it possible you unclipped part of the main room harness when installing the headers and it didn't get put back correctly? There is very little room around the engine bay where the harness runs and it could very well be burning when your headers heat up.

I'm only suggesting this because I worked on this huge harness and know the touch points very well after rerouting portions of it in my IS350 to fit the ISF motor. Additionally, C1249 - ABS, stop light switch circuit open indicates to me that a wire is unplugged or shorted. The Stop Light switch is a simple open/closed trigger mounted atop the brake pedal inside the cabin. It gets it wire feeds from the main room engine harness coming thru the driver side firewall. I would check your driver side manifold ASAP for possible wire contact.

xvector

mike, i know those were very random codes, but everything been OK for me after my easy fix.

snyper, any luck, any updates?

Snyperifle

xvector - I put in a new tank of gas but no luck. Still misfired.

mikellucci - Thanks for the tip I will check the harnesses further down the engine bay later today. I've only been checking if everything was plugged in. I just don't remember if there were wires up against the headers to begin with. Guess I'll find out

Gville350

iTrader: (10)

I assume you disconnected the battery during the alternator install?

After reading quite a few carbon build-up threads on here and how the symptoms are all over the place, I'm putting money on that. Your best bet would be to replace ALL aftermarket parts with stock before the dealership visit.

GL!

mikellucci

iTrader: (56)

Any update?

Just to make you guys laugh - I plugged into TechStream for the first time since my swap and I received the C1249 - ABS, stop light switch circuit open

Gville350

iTrader: (10)

^You swapped over a completely different motor into the car and that's all it found? LOL!

Snyperifle

Well I guess an update is that I did check for any wires that are bumping into the headers and such but no luck. You said the space was really cramped back there Mikellucci but maybe it isn't the case for the 2.5L V6 lol. I had at least 2-3 inches from the headers to any wire looms. I could see how it would be cramped with the 3.5L or the 5.0L though. I got an appointment with the dealership in the morning to see how it goes.

The really weird thing is that Wednesday night I spend over an hour trying to get the car to misfire. I could usually do it in like 3 minutes by doing some hard pulls but I couldn't get it that night. I did like 30 WOTs but no misfire or engine stuttering, so I parked for the night. Then the next morning when I did a cold start, my car immediately misfired lol. Today I could not get the car to misfire either.

I guess good news is that in the past 3 days it only misfired once where it used to misfire basically every time I turned on the car. Maybe my car was having mood swings.

Mikellucci! If you figure out how to fix that code, tell me how! I pulled up my codes again today and that came up.

xvector

i swaped a 350 engine on my 07 250 and i got abs issues, i believe i should change the abs pump and see how it goes. no scanner can connect to the abs unit and i believe this should be a fix for this. after that... no code no nothing.

snyper hope you fix it soon

Snyperifle

Well I dropped my car off on Friday at 9:30am. Still haven't heard anything from the dealership but I do know they started looking at my car around 2:00 that day. Patiently waiting :/

Gville350

iTrader: (10)

Any updates today?

Snyperifle

Yes, the dealership called and said that they could NOT replicate any misfires. I picked up my car and less than 20 minutes later, I got a misfire at a red light. While I was stopped, the car started shaking so I whipped out my phone camera. The car misfired when I applied gas, got it all on camera.

Brought the car back to the dealer, they're gonna take a look at it again.

Snyperifle

Lol okay I just received a call just now from my service advisor. He made it a point that a number of techs diagnosed my car but they could not make my car misfire.

There are a couple notes.
The main thing they are looking for here is carbon build up symptoms, as each week they have a couple cars in here doing the carbon build up CSP. The head tech said that they CANNOT do anymore diagnostics because I am missing my catalytic converters in my headers, causing it to put a CEL on the dash. He also said that because the lack of catalytic converters in my headers, the carbon build up CSP would not be under warranty.

My thoughts are:
2 weeks ago, my car would misfire *every* time I went for a drive. It is difficult for me to believe that the dealership, which has had my car since Friday and had 3 good days to work, could not get my car to misfire at all.
It is also difficult for me to understand why diagnosing would be difficult because a CEL light is on from catless heads. If I didn't have TPMS sensors, would a low tire pressure light also make it difficult to diagnose an engine issue? Doesn't make sense to me. They are plugging in a laptop with the Toyota Techstream program, yes? Just ignore where it says insufficient catalytic converter efficiency.
And lastly my catless heads voiding warranty work. If I'm not mistaken, the Magnuson-Moss Warranty Act prevents warranty work from being denied because of aftermarket work on the vehicle, if that work isn't causing the problem. If carbon build up is my issue, what do my catless heads have anything to do with it? Probably 99% of 2IS or 3GS do not have catless heads and a large number have carbon build up. My changing to catless heads isn't the problem. It is the lack of cleaning in the ports, not catalytic converters, causing the issue.

It is ticking me off that I came to the dealership to make use of their master techs and millions of dollars of equipment, they could not get my car to misfire let alone start working on the issue. I thought taking it to the dealership was a sure fix, because I'm tired of trying to fix it myself.