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Feels like misfires under boost, some popping. No codes.
Ls3, 6676 twins, E85, 4th gen.
Car just finished and tuned. Drove 50 miles w out issues and plenty of hard pulls. It’s amazing (first boosted car).
It started running rough at idle, scanner was plugged in, P0200, ended up being loose injector connection…so happy. Only drove it this way for a few minutes without much load. Took it easy and SES light turned off. P0200 went to pending and eventually cleared.
Jumped on the highway and thought I felt a misfile when under boost (4-5psi). Then it became obvious next 1/2 throttle pull and worse each time I tried (3more times before I parked it). also, exhaust pops started the last couple small pulls.
FP seems fine (steady 53ish). FI connectors are fine, no exhaust leaks.
I’ve read on here it could be wires, plugs, bad grounds, lifters, etc.
considering the chain of events, am I lucky enough for it to be fouled plugs or burnt wire?
seems to drive just fine when not under boost. Maybe a little pop here and there.
puiled 2 plugs. The one w the disconnected FI had bright white porcelain w a tan spot on one side. The strap looked coroded. The other was the same w no tan spot.
If you have a thermal temp gun, use it, if you don't, get one. If you hit the tubes right as they exit the block, they should be pretty consistent. It's likely you won't hear it miss at idle but it probably is, at minimum a incomplete burn.
As said, logs are also good to have.
If you have a thermal temp gun, use it, if you don't, get one. If you hit the tubes right as they exit the block, they should be pretty consistent. It's likely you won't hear it miss at idle but it probably is, at minimum a incomplete burn.
As said, logs are also good to have.
it’s on a factory computer so no data log. The fuel pressure came down to below 50 (was mid 50’s when I picked it up and throughout most of the first tankful) so I changed the fuel filter. Pressure started at 60psi and by the time the car warmed up it was just below 50psi again.
the dual lambda gauge read 10bps higher on one side at startup but leveled out when warmed up.
I took temp readings of the tubes, which are wrapped, and there is some variance. Plugs still look consistent and good. I didn’t drive it but the motor is shaking at idle and I can hear little bit of inconsistent popping in the exhaust when holding at 2-3k rpm.
1 420
3 340
5 460
7 470
2 460
4 480
6 500
8 440
I can’t get my mind off of the fuel pressure; the car drove great after I picked it up (55ish psi FP), only a few gallons of e85 left (75% ethanol per gauge) and through most of the 1st tankful I put it (70% ethanol, 55ish psi). Before I filled up for the second time is when I started noticing the popping and slight sputtering (lower 50s psi FP). I filled it up (70% ethanol) drove it home and it was at its worst popping/sputtering without boost (high 40s psi FP).
If you have a thermal temp gun, use it, if you don't, get one. If you hit the tubes right as they exit the block, they should be pretty consistent. It's likely you won't hear it miss at idle but it probably is, at minimum a incomplete burn.
As said, logs are also good to have.
Water in a spray bottle will tell you the same story. It should evaporate immediately when you spray it right by the port. Problem cylinder will not immediately evaporate it.
check the compression. pull all the plugs. You may have a busted ring land (stock pistons?) or a damaged valve (stock valves?). Or a blown head gasket. Compression test will tell you if you have a engine problem.
check the compression. pull all the plugs. You may have a busted ring land (stock pistons?) or a damaged valve (stock valves?). Or a blown head gasket. Compression test will tell you if you have a engine problem.
motor has forged internals and luckily no ticks but I suppose it could be a head gasket or one of the items mentioned. The motor was bench dyno’d for breakin by the machine shop. Is the lower temp on one of the cylinders pointing in that direction?
Can you unplug individual coils/injectors and see if there is any change to help identify which hole might be dead or having an issue?
Maybe start with the hole that is down on temperature?
Then swap coils/injectors around and see if the condition follows?
You can data log with the stock computer, but you'll need to get HP Tuners or EFI Live.
If you're going to be playing with turbo LS stuff, a cheap laptop and HP Tuners is a must have in my opinion.
If you go to HP Tuners website, they list the minimum specs required to run the software which isn't much.
I think I paid $400 for a brand-new laptop on a black Friday sale, the software is free to download, you'll need to buy the cable and adapter and a credit to use it.
Setting up the software and scanner PID's is little complex but there are many YouTube videos on how to do it.
I am not tech savvy whatsoever and I was able to figure it out, plus you have plenty of guys on here who can help, or you can pay someone.
Pat G. remote tunes all my stuff, he is top notch, hasn't blown up any of my stuff up yet and I beat on it like I stole it lol.
I'd be happy to send you my PID setup if you like if you go that route, save you some time.
If you go to HP Tuners website, they list the minimum specs required to run the software which isn't much.
I think I paid $400 for a brand-new laptop on a black Friday sale, the software is free to download, you'll need to buy the cable and adapter and a credit to use it.
Setting up the software and scanner PID's is little complex but there are many YouTube videos on how to do it.
I am not tech savvy whatsoever and I was able to figure it out, plus you have plenty of guys on here who can help, or you can pay someone.
Pat G. remote tunes all my stuff, he is top notch, hasn't blown up any of my stuff up yet and I beat on it like I stole it lol.
I'd be happy to send you my PID setup if you like if you go that route, save you some time.
thanks! It is confusing but if I do have a 10yr old computer that was very stout back then and still works well. I found a USB to OBD2 cable on Amazon for $25..and I think I already have one from when I needed to program a new key for a different car.
Also, the speed shop said they purchased a $100 credit for the new stock computer I needed, so that might already be taken care of(?). So, with the HPT free download I might be further ahead than I think with running a log.
I’ll do the download tonight, find that cable and watch some videos. Thanks!!
You have to have the HPT connection to be able to do the scan unless something has been changed.
You don't mention it, what plugs do you have? Hard to tell from the pic but looks like a decent gap in it. When I first did my turbo I had TR55 plugs gapped at mid 30's and would progressively get worse and break up in boost. Switched to BR7EF and all issues went away. Other thing I've seen is super low timing can cause similar symptoms when too much fuel is introduced.
If you have constant pressure I would think you're fine on your fuel system. As others have mentioned, if you can get a log can help determine where the issue is. Make sure you get a wideband also otherwise you are blind to what the afr really is.
More power more money, welcome to the boosted life.
You have to have the HPT connection to be able to do the scan unless something has been changed.
You don't mention it, what plugs do you have? Hard to tell from the pic but looks like a decent gap in it. When I first did my turbo I had TR55 plugs gapped at mid 30's and would progressively get worse and break up in boost. Switched to BR7EF and all issues went away. Other thing I've seen is super low timing can cause similar symptoms when too much fuel is introduced.
If you have constant pressure I would think you're fine on your fuel system. As others have mentioned, if you can get a log can help determine where the issue is. Make sure you get a wideband also otherwise you are blind to what the afr really is.
More power more money, welcome to the boosted life.
I’ll need to watch some videos to fully understand what is needed to connect with HPT, as suggested above.
the TR6 were gapped at .045 and used by the speed shop to tune the car. I tried BR7EF plugs at .025 last night based on a post in my build thread; I mentioned this issue was being discussed on this forum and received questions/suggestions on my other thread.
Anyhow, with the new plugs I think the popping is gone but idle is rough, I need to double check wires are fully seated. The BR7EF was selected with the anticipation of turning up the boost to the upper teens in the near future and likely needing to re gap plugs tighter at that time.
I have a dual lambda gauge and once fully warmed it’s reading 0.9 in both banks at idle, sometimes w a 10bps variance between the two banks and higher variance when warming up. It was pretty steady at 1.0 when I picked up the car. After changing the plugs last night haven’t driven it yet, likely tomorrow.
You’re right, at this point considering what’s in this car a little more money to get set up w HPT should feel like a couple of bucks (comparatively at least). Haha.
thanks! It is confusing but if I do have a 10yr old computer that was very stout back then and still works well. I found a USB to OBD2 cable on Amazon for $25..and I think I already have one from when I needed to program a new key for a different car.
Also, the speed shop said they purchased a $100 credit for the new stock computer I needed, so that might already be taken care of(?). So, with the HPT free download I might be further ahead than I think with running a log.
I’ll do the download tonight, find that cable and watch some videos. Thanks!!
a usb to obd2 cable isn’t going to work. You have to buy the proprietary cable setup from hp tuners to use hp tuners. Even though they bought credit, that does not give you access. The credits are stored in the hp tuners box, which they own. You’ll have to buy your own. Depending on what you buy, it may come with credits, or it may not. You cannot use hp tuners logging software with a usb to obd2 cable either.
07-25-2024, 08:43 PM
Feels like misfires under boost, some popping. No codes. 
?? 