LSJ Tuning Help -- Random Misfires?

[tycoonbob]

Hi all, new around here and new-ish to HPT.

So I have a 2006 Cobalt SS with the LSJ engine. Mods:
TVS 1320 blower w/ 2.9" pulley
Siemens 80# Injectors
Shorty headers, catless downpipe
K&N CAI
Cooling mods

Most of the mods are new after doing some engine work. The car has new timing and balance shaft components, piston rings, head gasket, head has been worked over (resurfaced and valve job), new coils, new plugs (NGK 2667 gaped at 0.35"), and I think that's it. Everything else is stock (including the TB).

I've been working with a local-ish tuner on a E-85 tune (or really a E-70 tune because winter time here in Kentucky). By no means am I doubting my tuner, but I just would like a second set of eyes here. Since swapping the blower, injectors and going E...I've been dealing with misfires. Car is throwing 2 codes currently, P0300 (Random Misfire Detected) and P0017 (Crankshaft Position - Camshaft Position Correlation - Bank 1 Sensor B). Now I'm 99.99% positive the timing chain is timed correctly, and that the cam sensor housing is also set correctly. Both of those are pretty simple to do on this engine. The cam sensor housing I've set at least 4 times in the last 4 weeks just to be absolutely positive. Now I also think the previous owner did swap the crank sensor, but he never did a CASE relearn. I've tried twice to do a CASE relearn through HPT, but I'm not 100% if it worked. Still, I don't think this P0017 code would cause these misfires, or would it?

So with that said, I'm just running out of ideas here. Another set of eyes on my tune file would be greatly appreciated. I also have a log attached of the car idling at temp. You can see the car is idling about 300-400rpm higher than target, which is odd. Really looking for confirmation on the tune, or any ideas on what could be causing the misfires. Thanks in advance.

[TCSS07]

change your pe delay to 2k or so. you dont want pe to have a delay. i have it zeroed out in my tune
P0017 timing correlation. sure it could cause misfires if the mechanical timing is off because that will make the fuel injection timing incorrect which would cause misfires and possibly lean condition. your 100% sure its timed correct?
i dont know why you have boost control prop and integ gain set to 1.0 - id put that back to stock. it was .005 for prop and .001 for integ. i messed with those one time and made the car unstable
your running lean as hell, your o2 sensor is stuck lean and your idle map is 90kpa. so either your map sensor is screwing up or its just a result of the idle issue. make sure you dont have any vac leaks causing the idle to hang/causing the trim issue or exhaust leaks causing your trim issue.
disable burst knock or at least cut the table in half
maybe put your car in speed density mode and see if the idle comes back to normal to test to see if its the maf causing it
now you do know how to time it properly correct?. you need to match up the little cut/mark on the harmonic balancer to the line/mark on the front cover next to the oil pump valve (about 10 O'Clock) and then you time the cam sensor hex to the housing and install it
was the engine running normal before and then started acting like this after the blower swap and stuff? when was the engine rebuilt? was this all done at the same time? check compression and cylinder leakage? bad fuel? when the rings were replaced im assuming you did pistons also? cylinder walls ok? who did the rebuild?

[tycoonbob]

Hi @TCSS07. I appreciate you taking your time to respond.

So to answer a few questions;
1) I bought the car from a guy who wasn't able to get it running, so the car has never run good since I've owned it. He replaced the timing chain, but was having compression issues on cyl 1 and could never get the car to run. I got the car, did some diags (compression, leakdown, fuel pressure test, etc, etc) and decided to just pull the head and send it off. Dropped the head off at a machine shop where they dissembled, cleaned, pressure tested, and did a valve job. The previous owner was convinced it had bent valves, but machine shop checked all the valves and they were fine. They did mention a couple exhaust valve seats had a bit of wear or something so they fixed that. So with the head being pulled, and not confident that the head was causing low compression, I decided to pull the pistons, install new rings and rod bearings, use a dingleberry hone on the cylinders, and reinstall. When the car went back together, I used a new head gasket, head bolts, coils, plugs, and the factory injectors. So pretty much everything that could be causing low compression should be addressed. After piston ring break-in (and this was on a stock tune, with stock injectors, m62 w/ stock pulley and whatever gasoline was already in the car), I did a compression test and all 4 cylinders were within 5 psi from each other, and were around 160. FWIW, I feel like my compression tester gauge may read a little low (it was some cheapo from Amazon).

2) So after break-in, I decided it was time to swap in mods and do tuning. So installed the TVS blower, 80# injectors, drained the fuel tank and put in 6 gallons of E85 from a local gas station (probably more like E70). Got a base tune from my tuner, and started there. Have gotten 2 revisions since, and things have gotten a little better. Now, you're probably wondering, did the car misfire before the mods and switch to E85? Well, I honestly don't know. I never logged misfires back then I know it had trouble idling, but I did drive the car a little bit. It ran, it was a little rough, but it ran. So I don't know.

So today...I pulled the valve cover, rotated the crank until cyl 4 was TDC, verified it was compression stroke (cam lobes were pointing up, not touching the springs), pulled the cam housing and it was lined up, verifying that cam sensor housing timing was correct. Wiped it down, pulled the cam sensor and cleaned it off, tested continuity and resistance across the sensor (outermost leads) and got readings, but didn't pay attention to either readings. This tells me the cam sensor is not 100% dead. I also test continuity on the ground lead of the connector, and got a reading (one probe on that lead, other probe on a ground point on the car). So that's a good sign. Also remember that my log above shows a reading on the cam sensor, so pretty confident the sensor is fine, and I know it was timed correctly, and am perfectly confident I timed it correctly when I put it back in just a little bit ago. I did not known about the line/mark on the front cover to use when lining up the cam housing, but I will double check that as well.

So then I rotated the piss out of the harmonic balancer bolt until the cam gears lined up with the timing marks. Intake cam gear is at ~2 o'clock, exhaust cam gear is at ~10 o'clock, color dot is pointing at colored links on the chain, so I'm at least sure the cam gears are timed correctly. Unfortunately I don't have time to pull the front cover to check the crank gear, but I will later this evening or tomorrow. Again, I'm fairly confident that I timed it correctly a couple weeks ago, but no harm in checking to make sure.

So once I check that crank gear, I'm going to put it back up, warm the engine, and do a compression test. I noticed the plugs that are in the car (which seriously have less than an hour of runtime on them) were looking pretty black. Uh-oh. I'm concerned I might be getting some oil past the pistons, and if that's the case...new block. But, for all 4 pistons to have that same problem and cause misfires right after a rebuild? Eh, I'm not convinced.

To answer other questions, cylinder walls were damage free, and scratched up nicely when I honed it. Pretty good crosshatch, but probably not at 45 degrees. I tried, but I didn't remove the oil squirters and I didn't want to hit them with the hone. It's totally possible I got bad fuel. I don't know how much my local station sells this time of year, so I don't know if it's been sitting a while. I feel I drained the tank as good as I could, but it's always possible there was a bit left in the tank and that diluted the 6 gallons of E I put in even further. Which with a target stoich of 10.1, I would think I'd be running pretty rich if it was a high % of gas. On a side note, I did get my AFR gauge, and I did buy Pro for my MPVI2 and got my adapter in the mail today, so I can use the analog signal once I hook up the AFR. My downpipe has a bung welded in for a wideband, but the sensor hits some metal piece on top of the rear transmission mount, so not sure what to do about that. May have to pull the downpipe and get another bung welded on.

Shew...I think that's everything. I'm very new to tuning, but I'm doing my best to learn. Reading a lot, videos, looking at my logs and tune file...but I'm far from experienced on the topic. I'm the kind of person that likes to know everything about something so I can be certain, and tuning is new to me so I personally can't tell if my tune is correct. Like I said, my tuner is well versed in these engines (to my knowledge, at least), and I trust him. But just like a prognosis from a doctor, a second opinion doesn't hurt.

Thanks!!!

[TCSS07]

what you have listed is that the full mod list? if not please list all the engine mods. well isnt that a lot to choke on...lol - great information about the situation

1.) Did you reuse the old pistons? I dont know what the normal compression should read since ive never actual done one on my own vehicle to have as a reference - maybe i should just to know. but if they are all reading the same id say your probably ok unless there suppose to all read like 200psi or something. i cant find a specific psi on GM Service information. it mainly talks about if the highest cylinder is 150psi then no other cylinder should be any lower than 70%((105psi) based off highest of 150psi) of that value but doesn't say what base psi is normal. but for me thats huge drop in allowed psi but i wouldn't accept anything less than 15% but thats just my opinion on that matter

2.)its probably safe to say it had the issue before the blower swap if it was running rough. before the blower,injectors, e85 - did you have the idle issue as well or is that new development? tps% should be around 14-17% at idle yours is stuck at 23.5% which to me is telling me something is making it stay there like a vac leak or something because the idle settings are stock for a factory lsj tb or maybe the ecm cant/wont relearn the idle home position causing it to hang but i wouldnt go out and buy a new ecm or its possible because the trims are so out of wack its causing problems but in my experience a vac leak will cause a hang idle before running lean would - lean would account for misfires though. also for idle kpa you should probably in between 30-40kpa - not 90kpa but again that may be because of the idle issue - i idle around 70 kpa but i have zzp stage 3 cams

3.) my car sets a p0017/p0300 also but mine is either because i was a cunt hair off when i installed my cam sensor or the zzp cam hex is off just a bit. either way i know its timed right so i disabled the dtc and misfire codes because im cammed and it causes misfire because of the cams and engine balance is off for the mods. gm actually has a service bulletin about aftermarket lightweight flywheels and s/c pulleys causing misfires setting the light - which cracks me up since they offer the gm stage 1,2 and 3 kits lol - granted stage 1 is just calibration and injectors. i got sick of it and shut it off. but i know how my car runs and i know if its running right or wrong so it doesnt concern me shutting the codes off. i do not recommend it for the average person however.

the spark plugs are looking black probably from all the fuel the cars dumping as well - black usually would come from carbon - too much fuel. look at your log. your short term fuel trims are pegged lean followed by the ltft which means its just adding so much fuel - max for stft is 30% and ltft is 20%. please make sure you have everything hooked up properly and no vac leaks - vac lines,intake gasket,sc gasket,pcv,fuel injector insulators/o rings or exhaust leaks ... anything. you may have to smoke test the induction system to see if anything is leaking. after you do some testing id suggest maybe putting a new o2 sensor in and map sensor and go from there because tune wise i dont see anything that would cause whats going on unless your airflow model is off by that much which i suppose is possible since e85 requires 30% more fuel just off the get go so maybe take your maf and enter 1.3 in the box and multiply the maf chart by 30% and see if it gets better or i suggested going to speed density mode only and see if the idle clears up to eliminate the maf as the culprit. theres some things id change (like what i said in my other post) but nothing that would change the issue going on atm. but id def drop that prop and integ numbers back to stock tho

other things than can cause misfires are but not limited to plugs,coils,cracked pistons/low compression (the new gen malibu 1.5l and cruze 1.4l - major problem),02 sensors,collapsed lifters, broken valve springs, faulty fuel injectors,bad fuel, incorrect tune/fueling related/vac leaks, running lean causing lean misfires, sticky valves but generally goes away when idle is raised but has a normal idle to start, bad camshaft/lobes and rockers, fuel pump, incorrect engine timing

for speedy density/ve mode only you need to disable the maf by going to engine diag maf high hz set to 0 and dtcs p0101-p0103 to mil on first error, raise dynamic airflow to 8000 disable and 7900 re enable, copy high octane spark to low octane spark because ve mode defaults to the low octane spark chart

what was the fuel pressure at? 58-60psi is normal

[cobaltssoverbooster]

if it has comp cams then those can throw cam codes.
was the head decked? and how much?

[TCSS07]

overbooster - yeah i forget about the decking of the head sometimes but even if that were the case i dont think you would get driveability problems because of that

[steelmesh]

Hi all, new around here and new-ish to HPT.

So I have a 2006 Cobalt SS with the LSJ engine. Mods:
TVS 1320 blower w/ 2.9" pulley
Siemens 80# Injectors
Shorty headers, catless downpipe
K&N CAI
Cooling mods

Most of the mods are new after doing some engine work. The car has new timing and balance shaft components, piston rings, head gasket, head has been worked over (resurfaced and valve job), new coils, new plugs (NGK 2667 gaped at 0.35"), and I think that's it. Everything else is stock (including the TB).

I've been working with a local-ish tuner on a E-85 tune (or really a E-70 tune because winter time here in Kentucky). By no means am I doubting my tuner, but I just would like a second set of eyes here. Since swapping the blower, injectors and going E...I've been dealing with misfires. Car is throwing 2 codes currently, P0300 (Random Misfire Detected) and P0017 (Crankshaft Position - Camshaft Position Correlation - Bank 1 Sensor B). Now I'm 99.99% positive the timing chain is timed correctly, and that the cam sensor housing is also set correctly. Both of those are pretty simple to do on this engine. The cam sensor housing I've set at least 4 times in the last 4 weeks just to be absolutely positive. Now I also think the previous owner did swap the crank sensor, but he never did a CASE relearn. I've tried twice to do a CASE relearn through HPT, but I'm not 100% if it worked. Still, I don't think this P0017 code would cause these misfires, or would it?

So with that said, I'm just running out of ideas here. Another set of eyes on my tune file would be greatly appreciated. I also have a log attached of the car idling at temp. You can see the car is idling about 300-400rpm higher than target, which is odd. Really looking for confirmation on the tune, or any ideas on what could be causing the misfires. Thanks in advance.

If you can feel the misfire during WOT (torque loss "blip"), then you need to close your spark plug gaps further. Like 0.028-0.030. It's that simple, again for misfires during WOT pulls.

[Ritter18252]

Hi @TCSS07. I appreciate you taking your time to respond.

So to answer a few questions;
1) I bought the car from a guy who wasn't able to get it running, so the car has never run good since I've owned it. He replaced the timing chain, but was having compression issues on cyl 1 and could never get the car to run. I got the car, did some diags (compression, leakdown, fuel pressure test, etc, etc) and decided to just pull the head and send it off. Dropped the head off at a machine shop where they dissembled, cleaned, pressure tested, and did a valve job. The previous owner was convinced it had bent valves, but machine shop checked all the valves and they were fine. They did mention a couple exhaust valve seats had a bit of wear or something so they fixed that. So with the head being pulled, and not confident that the head was causing low compression, I decided to pull the pistons, install new rings and rod bearings, use a dingleberry hone on the cylinders, and reinstall. When the car went back together, I used a new head gasket, head bolts, coils, plugs, and the factory injectors. So pretty much everything that could be causing low compression should be addressed. After piston ring break-in (and this was on a stock tune, with stock injectors, m62 w/ stock pulley and whatever gasoline was already in the car), I did a compression test and all 4 cylinders were within 5 psi from each other, and were around 160. FWIW, I feel like my compression tester gauge may read a little low (it was some cheapo from Amazon).

2) So after break-in, I decided it was time to swap in mods and do tuning. So installed the TVS blower, 80# injectors, drained the fuel tank and put in 6 gallons of E85 from a local gas station (probably more like E70). Got a base tune from my tuner, and started there. Have gotten 2 revisions since, and things have gotten a little better. Now, you're probably wondering, did the car misfire before the mods and switch to E85? Well, I honestly don't know. I never logged misfires back then I know it had trouble idling, but I did drive the car a little bit. It ran, it was a little rough, but it ran. So I don't know.

So today...I pulled the valve cover, rotated the crank until cyl 4 was TDC, verified it was compression stroke (cam lobes were pointing up, not touching the springs), pulled the cam housing and it was lined up, verifying that cam sensor housing timing was correct. Wiped it down, pulled the cam sensor and cleaned it off, tested continuity and resistance across the sensor (outermost leads) and got readings, but didn't pay attention to either readings. This tells me the cam sensor is not 100% dead. I also test continuity on the ground lead of the connector, and got a reading (one probe on that lead, other probe on a ground point on the car). So that's a good sign. Also remember that my log above shows a reading on the cam sensor, so pretty confident the sensor is fine, and I know it was timed correctly, and am perfectly confident I timed it correctly when I put it back in just a little bit ago. I did not known about the line/mark on the front cover to use when lining up the cam housing, but I will double check that as well.

So then I rotated the piss out of the harmonic balancer bolt until the cam gears lined up with the timing marks. Intake cam gear is at ~2 o'clock, exhaust cam gear is at ~10 o'clock, color dot is pointing at colored links on the chain, so I'm at least sure the cam gears are timed correctly. Unfortunately I don't have time to pull the front cover to check the crank gear, but I will later this evening or tomorrow. Again, I'm fairly confident that I timed it correctly a couple weeks ago, but no harm in checking to make sure.

So once I check that crank gear, I'm going to put it back up, warm the engine, and do a compression test. I noticed the plugs that are in the car (which seriously have less than an hour of runtime on them) were looking pretty black. Uh-oh. I'm concerned I might be getting some oil past the pistons, and if that's the case...new block. But, for all 4 pistons to have that same problem and cause misfires right after a rebuild? Eh, I'm not convinced.

To answer other questions, cylinder walls were damage free, and scratched up nicely when I honed it. Pretty good crosshatch, but probably not at 45 degrees. I tried, but I didn't remove the oil squirters and I didn't want to hit them with the hone. It's totally possible I got bad fuel. I don't know how much my local station sells this time of year, so I don't know if it's been sitting a while. I feel I drained the tank as good as I could, but it's always possible there was a bit left in the tank and that diluted the 6 gallons of E I put in even further. Which with a target stoich of 10.1, I would think I'd be running pretty rich if it was a high % of gas. On a side note, I did get my AFR gauge, and I did buy Pro for my MPVI2 and got my adapter in the mail today, so I can use the analog signal once I hook up the AFR. My downpipe has a bung welded in for a wideband, but the sensor hits some metal piece on top of the rear transmission mount, so not sure what to do about that. May have to pull the downpipe and get another bung welded on.

Shew...I think that's everything. I'm very new to tuning, but I'm doing my best to learn. Reading a lot, videos, looking at my logs and tune file...but I'm far from experienced on the topic. I'm the kind of person that likes to know everything about something so I can be certain, and tuning is new to me so I personally can't tell if my tune is correct. Like I said, my tuner is well versed in these engines (to my knowledge, at least), and I trust him. But just like a prognosis from a doctor, a second opinion doesn't hurt.

Thanks!!!