First start up - running very rough and backfiring
Thread Starter
Launching!
Joined: Feb 2012
Posts: 263
Likes: 50
From: IL, USA
First start up - running very rough and backfiring So today I did the initial start up with my LSX build with LS3 heads and the Magnuson SC. I did change the cam to a TSP Stage 3 cam (dot to dot on engine timing). It does not want to idle, backfires alot if I try to hold the gas pedal and idle it at 800 - 900 rpm and if I take it up to around 2000 rpm, its very rough almost like a misfire. It also fouled the plugs (black). I replaced the plugs (new BR7EF .032 gap), replaced the coils with another working set I have and same thing again. Did not change plug wires (msd) yet... I do have a Tech2 and funny thing is its not showing any misfire on it on all 8 cylinders...
Do you guys think the old tune that was done for this exact setup but with a stock cam is the problem?
Any suggestions guys? Thx.
Car is an 04 C5 btw.
Do you guys think the old tune that was done for this exact setup but with a stock cam is the problem?
Any suggestions guys? Thx.
Car is an 04 C5 btw.
So today I did the initial start up with my LSX build with LS3 heads and the Magnuson SC. I did change the cam to a TSP Stage 3 cam (dot to dot on engine timing). It does not want to idle, backfires alot if I try to hold the gas pedal and idle it at 800 - 900 rpm and if I take it up to around 2000 rpm, its very rough almost like a misfire. It also fouled the plugs (black). I replaced the plugs (new BR7EF .032 gap), replaced the coils with another working set I have and same thing again. Did not change plug wires (msd) yet... I do have a Tech2 and funny thing is its not showing any misfire on it on all 8 cylinders...
Do you guys think the old tune that was done for this exact setup but with a stock cam is the problem?
Any suggestions guys? Thx.
Car is an 04 C5 btw.
Do you guys think the old tune that was done for this exact setup but with a stock cam is the problem?
Any suggestions guys? Thx.
Car is an 04 C5 btw.
Thread Starter
Launching!
Joined: Feb 2012
Posts: 263
Likes: 50
From: IL, USA
TECH Fanatic
Joined: Jan 2022
Posts: 1,034
Likes: 468
From: Seattle
double and triple checked full spark plug and coil engagement?it sounds like a spark / timing issue. even if the tuning was remotely close it wouldn't backfire right?
Thread Starter
Launching!
Joined: Feb 2012
Posts: 263
Likes: 50
From: IL, USA
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Thread Starter
Launching!
Joined: Feb 2012
Posts: 263
Likes: 50
From: IL, USA
Oh not too much other than work and dropping a few lines here and there on LS1Tech. Looking forward to hearing an idle clip once you get it where it needs to be.
Last edited by 01CamaroSSTx; Jan 28, 2022 at 04:45 PM.
Maybe the coil pack wires need to be switched from side to side, drivers #1 cylinder has purple trace wire & #7 has red trace wire. On the passenger bank things are reversed the #2 cyl has the red trace wire and #8 has the purple trace wire for the coil packs. Double check and see if this is right?
Thread Starter
Launching!
Joined: Feb 2012
Posts: 263
Likes: 50
From: IL, USA
Thanks for all the suggestions! Just thought I'd update what the problem was. The car uses a 58x to 24x box (Lingenfelter TRG-002). Apparently this device MUST be connected directly to the cam sensor and not thru the short harness that usually goes to the sensor. I noticed that it was connected thru the harness and plugged it directly to the cam sensor, bam! No more backfiring or running rough. Had a tuner look at the crap tune the car came with and he did some quick adjustments to the tune so it's not fouling the plugs anymore and is idling ok. Funny thing is, this is how I bought the car and I always thought it had something to do with the tune when it took long to start and would fall flat on its face if I smashed the gas pedal or even give it a blip while in neutral... All these problems have disappeared now Guess the Stage 3 blower cam I put in really made it act up.
Anyways that was the problem Now to button things up, break the clutch in and then off to the tuner once this weather is back to "normal".
Guess the Stage 3 blower cam I put in really made it act up.Anyways that was the problem
Now to button things up, break the clutch in and then off to the tuner once this weather is back to "normal".Last edited by momofx; Feb 2, 2022 at 01:40 AM.
Thread Starter
Launching!
Joined: Feb 2012
Posts: 263
Likes: 50
From: IL, USA
in Pompano Beach, FL) installed it correctly but I should have known better as I found lots of other things done very sloppy and dangerous to say the least ie. live wire from battery to starter was damn near fried due to being so close by header, knock sensor wire burnt and cut on one side, etc. etc. 
Yeah I don't like having constant power down to the starter. Ford did it right by having a starter solenoid on the firewall and that's how both of my Camaros will be when I'm finished. Much easier to connect a remote starter switch for setting valves and performing compression tests.
My daughter ran into trouble with her truck acting up and she described smelling wires burning. After shaking the power wire and seeing sparks from below I was able to determine where her problem was and why she was eventually leaking engine oil. Apparantly the previous owner had changed the starter at some point but forgot to bolt the power wire back down to the frame which eventually led to the wiring melting a hole in the dipstick tube about 6-8 inches up from where it inserts into the block.
Last edited by 01CamaroSSTx; Feb 5, 2022 at 10:24 AM.
Teching In
Joined: Feb 2022
Posts: 13
Likes: 1
I did a rebuild from a stock lm7 to a stock everything except btr stage 2 cam and a handful of new parts and my truck was for the most part was undriveable. I was lucky to have a tuner close to me so I could drive it there but if I had to go to the next town over I would have had to trailer it there. It died on me 3 times getting there. Id say have a tuner check out the tune tables