MNcarbturbo
What's Fuel Injection?
I put together a 4.1 SFI setup that I swapped into an 80 century wagon this winter. Fresh rings and bearings, dingle ball hone on a clean 4.1 .030 block, hyper .030 bottom end, stock LC2 setup (turbo intercooler ect). Maf translater with LT1 Maf, l67 injectors at 4 BAR with adjustable FPR and matching chip, new caspers LED cam sensor, scanmaster. Just want a fun cruiser.
When putting the engine together I had a bad coil. Engine ran good cold but misfired under boost. Ohmed coil open across 2 pairs of posts and like 20k Ohm occross the other pair. I purchased a new to me, used but known good coil and module online, it ohmed at 11.5k Ohm.
Been working out some bugs and took it to the track a few weeks ago. 1st pass was a light low boost roll out shake down and it ran a high 14. 2nd pass it started running crappy half way down the track and got to the pits and was hard misfiring and smelt rich.
The parts I put the LC2 setup together with were parted out in the early 00's and the fuel rail was rusty from sitting for 20 years exposed to air, I vinegar dipped and cleaned it out with a large copper wire when I put the setup together and had plugged 2 injectors previously so I thought I plugged another injector. Limped the car home, swapped injector to another l67 white inejector, still misfired but better. #4 was very fuel smelling and my IR thermometer said it was burning cold. Let the engine dry fuel out, put it back together and still misfired. Basically I determined later on that my coil went dead causing weak #4 spar I think which caused #4 to stop igniting and flooded the cylinder
Checked compression, good 125-135 PSI on all 6. Did a leak down since I assumed I could have hydro locked #4 and pinched a ring or popped a head gasket, check the link for the youtube vid but it was fine. Almost no pressure drop, no air flow, no bubbles out the rad. Also put my dial indicator on the #4 exhaust and intake pushrods to check cam isn't wiped and they were in spec for lift comparing to #2. Cam is an erson 200ish duration mild cam from the mid 90's I got when I bought the 4.1 long block.
After checking a bunch of mechanical stuff since it was still misfiring, but not smelling of fuel I checked the coil and it was high ohms like 17-18k Ohm on all 3 sets of post. Coil and module only had 100 miles on but nothing mechanical could be found so I thought I had a bad coil. I would take it for a drive and it didnt smell of fuel but #4 was burning cold by about 100F and would pop, miss, and run like garbage. Assumed the coil reads bad, so the coil is bad.
Got sick of buying expensive coils that blow up so I bought a dynamic EFI LS coil near plug system and used some heat sink LS truck coils I had on the shelf. Got setup put together and started, ran significantly better. I used the same "new to me" ignition module that was under the bad coil I had 100 miles on. Engine still studdered, and misfired under boost. Could feel a miss at idle in gear when creeping in reverse or drive. Overall better than with the stock type 1 module and coil but not 100%. Maybe 40% fixed.
Thought I might have a bad module so I put the old module on that I had with the bad coil when I put the engine together this winter. This solved the misfire under boost and cleaned it up significantly. However, it still has a light throttle cruise miss and for sure a miss in gear when warm at idle. 80% fixed.
All cylinders burn within 20F of 600F right after a light drive around but #4 is 50-100F colder. Car runs good under boost.
I took a video of unplugging coils. You can hear the engine chug a bit at idle when everything is plugged in. I unplug #4 coil and it gets moderately worse but not much. Unplug any other coil and the engine for sure has a misfire and even died when i unplugged #3. #4 sounds and feels like it has a 50% miss at high vacuum situations.
I have checked plugs and they look good, #1 is top, #3 is bottom right, #4 is bottom left. #4 might have a light brown tint to the ceramic? If the 1/4 coil wiring was bad I should see little to no change when unplugging the #1 coil since its waste spark OR it would also burn cooler, but it doesn't. #1 is burning good.
Anybody have a clue what causes a 50% miss when all mechanical and electronic parts seem to check out? Do I just throw another ignition module at it? Pull the head off and check head gasket?
When putting the engine together I had a bad coil. Engine ran good cold but misfired under boost. Ohmed coil open across 2 pairs of posts and like 20k Ohm occross the other pair. I purchased a new to me, used but known good coil and module online, it ohmed at 11.5k Ohm.
Been working out some bugs and took it to the track a few weeks ago. 1st pass was a light low boost roll out shake down and it ran a high 14. 2nd pass it started running crappy half way down the track and got to the pits and was hard misfiring and smelt rich.
The parts I put the LC2 setup together with were parted out in the early 00's and the fuel rail was rusty from sitting for 20 years exposed to air, I vinegar dipped and cleaned it out with a large copper wire when I put the setup together and had plugged 2 injectors previously so I thought I plugged another injector. Limped the car home, swapped injector to another l67 white inejector, still misfired but better. #4 was very fuel smelling and my IR thermometer said it was burning cold. Let the engine dry fuel out, put it back together and still misfired. Basically I determined later on that my coil went dead causing weak #4 spar I think which caused #4 to stop igniting and flooded the cylinder
Checked compression, good 125-135 PSI on all 6. Did a leak down since I assumed I could have hydro locked #4 and pinched a ring or popped a head gasket, check the link for the youtube vid but it was fine. Almost no pressure drop, no air flow, no bubbles out the rad. Also put my dial indicator on the #4 exhaust and intake pushrods to check cam isn't wiped and they were in spec for lift comparing to #2. Cam is an erson 200ish duration mild cam from the mid 90's I got when I bought the 4.1 long block.
After checking a bunch of mechanical stuff since it was still misfiring, but not smelling of fuel I checked the coil and it was high ohms like 17-18k Ohm on all 3 sets of post. Coil and module only had 100 miles on but nothing mechanical could be found so I thought I had a bad coil. I would take it for a drive and it didnt smell of fuel but #4 was burning cold by about 100F and would pop, miss, and run like garbage. Assumed the coil reads bad, so the coil is bad.
Got sick of buying expensive coils that blow up so I bought a dynamic EFI LS coil near plug system and used some heat sink LS truck coils I had on the shelf. Got setup put together and started, ran significantly better. I used the same "new to me" ignition module that was under the bad coil I had 100 miles on. Engine still studdered, and misfired under boost. Could feel a miss at idle in gear when creeping in reverse or drive. Overall better than with the stock type 1 module and coil but not 100%. Maybe 40% fixed.
Thought I might have a bad module so I put the old module on that I had with the bad coil when I put the engine together this winter. This solved the misfire under boost and cleaned it up significantly. However, it still has a light throttle cruise miss and for sure a miss in gear when warm at idle. 80% fixed.
All cylinders burn within 20F of 600F right after a light drive around but #4 is 50-100F colder. Car runs good under boost.
I took a video of unplugging coils. You can hear the engine chug a bit at idle when everything is plugged in. I unplug #4 coil and it gets moderately worse but not much. Unplug any other coil and the engine for sure has a misfire and even died when i unplugged #3. #4 sounds and feels like it has a 50% miss at high vacuum situations.
I have checked plugs and they look good, #1 is top, #3 is bottom right, #4 is bottom left. #4 might have a light brown tint to the ceramic? If the 1/4 coil wiring was bad I should see little to no change when unplugging the #1 coil since its waste spark OR it would also burn cooler, but it doesn't. #1 is burning good.
Anybody have a clue what causes a 50% miss when all mechanical and electronic parts seem to check out? Do I just throw another ignition module at it? Pull the head off and check head gasket?
