LS1 troubleshooting
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LS1 troubleshooting LS swap this LS1 from a 98 vette to a 67’ camaro. Yesterday was the first time I started the car since I rebuilt it back in April. Added TSP cam and all the supporting mods. Also has a stand-alone PSI LS1 wiring harness. First thing I noticed when my dad started the car was a little smoke coming out of the passenger headers where they mount to the heads. The motor wouldn't stay on below 1500 rpm, it wouldn’t idle on its own. And huge popping coming from the exhaust. misfiring? I can also visually see the motor shake when those loud pops occurred. Oil pressure was fine at 65-70 psi (mechanical gauge for start up) Motor was on for about 3-4 minutes, (it has yet to be tuned) I used a temp laser tool to check the temperature of the header tubes individually. All passenger side headers were around 70-80 degrees and the drivers were around 320-330 degrees Fahrenheit. Most plugs where black, smelled like fuel, 2 of them were lightly darken, cylinder 8 was clean. My buddy is coming over on the weekend with a scan tool. What should I be looking for in the mean time? I heard a cam sensors can cause this but I’m just going off other threads.
Last edited by avchz; Nov 18, 2020 at 08:40 PM.
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From: Phantombullet
How are the injectors and coils wired for their required 12V? is there a seperate relay for each bank? Whatever the case, Id be checking they are getting 12V on each bank,
It would not be the cam sensor, that is only there for faster starting on these things, so that the PCM knows which coils to fire. If the cam sensor isnt working they still start, it just cranks for longer approx 50 percent of the time. When it doesnt start after a few seconds because the firing is off 180 (due to the PCM not knowing where the cam is), the PCM will flip the firing 180 and it will start... so i dont think its your cam sensor, the sensor not working right affects a number of other oem ECUs and they wont run right, but not these. Can always unplug it to see for yourself.
It would not be the cam sensor, that is only there for faster starting on these things, so that the PCM knows which coils to fire. If the cam sensor isnt working they still start, it just cranks for longer approx 50 percent of the time. When it doesnt start after a few seconds because the firing is off 180 (due to the PCM not knowing where the cam is), the PCM will flip the firing 180 and it will start... so i dont think its your cam sensor, the sensor not working right affects a number of other oem ECUs and they wont run right, but not these. Can always unplug it to see for yourself.
Thread Starter
Teching In
Joined: Oct 2020
Posts: 22
Likes: 1
How are the injectors and coils wired for their required 12V? is there a seperate relay for each bank? Whatever the case, Id be checking they are getting 12V on each bank,
It would not be the cam sensor, that is only there for faster starting on these things, so that the PCM knows which coils to fire. If the cam sensor isnt working they still start, it just cranks for longer approx 50 percent of the time. When it doesnt start after a few seconds because the firing is off 180 (due to the PCM not knowing where the cam is), the PCM will flip the firing 180 and it will start... so i dont think its your cam sensor, the sensor not working right affects a number of other oem ECUs and they wont run right, but not these. Can always unplug it to see for yourself.
It would not be the cam sensor, that is only there for faster starting on these things, so that the PCM knows which coils to fire. If the cam sensor isnt working they still start, it just cranks for longer approx 50 percent of the time. When it doesnt start after a few seconds because the firing is off 180 (due to the PCM not knowing where the cam is), the PCM will flip the firing 180 and it will start... so i dont think its your cam sensor, the sensor not working right affects a number of other oem ECUs and they wont run right, but not these. Can always unplug it to see for yourself.
this is a picture of the wiring diagram if that helps. Two 12v sources. Ignition on and the starter wire.
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I’m going to buy a spark tester today. I’ll keep you updated. It maybe could be stuck closed injectors. Idk how long those injectors have been sitting for.
