LT1 in 3rd gen, #8 Cylinder cold
09-23-2015, 06:27 PM
#1
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LT1 in 3rd gen, #8 Cylinder cold My friend has a Third Gen RS with an LT1 / T-56 swap. He's trying to get it running in time for the Ocean City, MD. Fall Cruise. The car was LT1 swapped years ago then he pulled the engine and let it sit for nearly 5 years. We picked up a '96 LT1 from a junkyard and he installed it. All is stock except for 1.6 Rockers, a CAI, and Edelbrock shorties with no other exhaust.
He installed it and fired it off. It ran rough and didn't rev. He bought a new OPTI a day later, installed it in my presence, and fired it off. It ran OK, seemed to clean out and rev OK after a minute. I left and hoped all was well.
A day later he texted me that the car doesn't want to rev cleanly, it seems to bog and run rough.
He swapped out the "junkyard" injectors and regulator with his old set. No change. With a temp gun he saw the following temps at the header primaries:
The even # bank of cylinders where around 240 degrees in temperature except for #8 which was cold at 120.
On the other side cylinders 5 and 7 were high in temp at 320.
He's going to pull plugs and swap to spare plug wires tonight if time permits. Is there anything else we should be considering? I've read that grounds or wires going to/from the injectors and computer might cause a "dead" cylinder. I never had an LT1 car so other than experience with traditional SBC, SBF, and LS1 I'm new to this.
Oh, the car has a '96 engine in it and all wiring is from a '94 and OPTI is a Vatozone Duralast. Thanks!
He installed it and fired it off. It ran rough and didn't rev. He bought a new OPTI a day later, installed it in my presence, and fired it off. It ran OK, seemed to clean out and rev OK after a minute. I left and hoped all was well.
A day later he texted me that the car doesn't want to rev cleanly, it seems to bog and run rough.
He swapped out the "junkyard" injectors and regulator with his old set. No change. With a temp gun he saw the following temps at the header primaries:
The even # bank of cylinders where around 240 degrees in temperature except for #8 which was cold at 120.
On the other side cylinders 5 and 7 were high in temp at 320.
He's going to pull plugs and swap to spare plug wires tonight if time permits. Is there anything else we should be considering? I've read that grounds or wires going to/from the injectors and computer might cause a "dead" cylinder. I never had an LT1 car so other than experience with traditional SBC, SBF, and LS1 I'm new to this.
Oh, the car has a '96 engine in it and all wiring is from a '94 and OPTI is a Vatozone Duralast. Thanks!
09-24-2015, 12:26 AM
#2
Does it feel like misfire?
I would check spark on 8. If there is spark then, check the injector. If both are fine then do compression test on cylinder 8.
I doubt bad ground, but worth moving harness around see if it changes any.
I would check spark on 8. If there is spark then, check the injector. If both are fine then do compression test on cylinder 8.
I doubt bad ground, but worth moving harness around see if it changes any.
Last edited by LT1; 09-24-2015 at 02:30 AM.
09-24-2015, 05:50 AM
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Thanks for the reply. What you posted is right along our path of troubleshooting. My buddy is going to pull the spark plug on 8 and look at it. After that the plan is swapping plug wires then the compression test.
Since I don't know the LT1 platform I was wondering if there was a wire or pin somewhere that could lead to this. The car doesn't sound like it has a misfire, simply seems like 8 isn't firing.
Since I don't know the LT1 platform I was wondering if there was a wire or pin somewhere that could lead to this. The car doesn't sound like it has a misfire, simply seems like 8 isn't firing.
09-24-2015, 06:14 AM
#4
I had this same problem but on #6 after the car sat for a long time. I was hearing a tick so I readjusted all my valves, no change. Then I verified all plug wires were clicked in tight. Then I pulled the plug wire and held a spare plug to a ground and ran it and watched for spark on that plug to verify it had spark and I saw spark but didn't pay attention to the pattern, so I deemed spark ok falsely. Then I swapped injectors from 4 and 6, no change. Then it got dark and I was still hearing the tick and noticed the coil wire was arcing to the ground strap near the coil every now and then. I wrapped the **** out of the coil wire in electrical tape and moved the ground strap. Tick was gone and that primary warmed up. The 8 year old plug wires had enough resistance that when it went to fire #6, the easiest path to ground was through the coil wire. I replaced all plug wires with brand new 8.2mm Taylor's with 40 or 60ohm resistance and it was perfect again.
When I thought back to the first spark test, the spark was not a consistent spark, it should be perfectly timed between sparks, and it was actually missing a few. When you do the spark test to a ground, watch it and verify it before moving on to injectors since swapping injectors is kind of a PITA. It could be that you adjusted the #8 rockers too tight and the valves are not closing all the way, unable to build compression, and unable to fire off.
When I thought back to the first spark test, the spark was not a consistent spark, it should be perfectly timed between sparks, and it was actually missing a few. When you do the spark test to a ground, watch it and verify it before moving on to injectors since swapping injectors is kind of a PITA. It could be that you adjusted the #8 rockers too tight and the valves are not closing all the way, unable to build compression, and unable to fire off.
09-24-2015, 08:47 AM
#5
My friend has a Third Gen RS with an LT1 / T-56 swap. He's trying to get it running in time for the Ocean City, MD. Fall Cruise. The car was LT1 swapped years ago then he pulled the engine and let it sit for nearly 5 years. We picked up a '96 LT1 from a junkyard and he installed it. All is stock except for 1.6 Rockers, a CAI, and Edelbrock shorties with no other exhaust.
He installed it and fired it off. It ran rough and didn't rev. He bought a new OPTI a day later, installed it in my presence, and fired it off. It ran OK, seemed to clean out and rev OK after a minute. I left and hoped all was well.
A day later he texted me that the car doesn't want to rev cleanly, it seems to bog and run rough.
He swapped out the "junkyard" injectors and regulator with his old set. No change. With a temp gun he saw the following temps at the header primaries:
The even # bank of cylinders where around 240 degrees in temperature except for #8 which was cold at 120.
On the other side cylinders 5 and 7 were high in temp at 320.
He's going to pull plugs and swap to spare plug wires tonight if time permits. Is there anything else we should be considering? I've read that grounds or wires going to/from the injectors and computer might cause a "dead" cylinder. I never had an LT1 car so other than experience with traditional SBC, SBF, and LS1 I'm new to this.
Oh, the car has a '96 engine in it and all wiring is from a '94 and OPTI is a Vatozone Duralast. Thanks!
He installed it and fired it off. It ran rough and didn't rev. He bought a new OPTI a day later, installed it in my presence, and fired it off. It ran OK, seemed to clean out and rev OK after a minute. I left and hoped all was well.
A day later he texted me that the car doesn't want to rev cleanly, it seems to bog and run rough.
He swapped out the "junkyard" injectors and regulator with his old set. No change. With a temp gun he saw the following temps at the header primaries:
The even # bank of cylinders where around 240 degrees in temperature except for #8 which was cold at 120.
On the other side cylinders 5 and 7 were high in temp at 320.
He's going to pull plugs and swap to spare plug wires tonight if time permits. Is there anything else we should be considering? I've read that grounds or wires going to/from the injectors and computer might cause a "dead" cylinder. I never had an LT1 car so other than experience with traditional SBC, SBF, and LS1 I'm new to this.
Oh, the car has a '96 engine in it and all wiring is from a '94 and OPTI is a Vatozone Duralast. Thanks!
Those are complete Chinese made garbage, take it back, get a refund, and buy a REAL opti for $400+ GM or MSD, accept no substitutes...
09-24-2015, 09:30 AM
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You guys had some good and inciteful advice which should help anybody else in troubleshooting similar problems.
My friend found and fixed the issue which was incorrect firing order. He had plug wires swapped at the OPTI. When I was at his house we fired the car without the radiator and gave it some low RPM revs which sounded OK without a noticeable miss or such. After getting the radiator in we re-started and shut down then I left. I guess the problem was noticeable at a certain RPM and beyond which I never witnessed.
I bought a K5 once from a Ford guy who had done new cap, rotor, plugs, and wires. The thing was a dog near 40MPH and at any RPM beyond 3k. The firing order was messed up. Once I put the wires in their correct places it ran fine. Had I heard the Camaro rev up I might have had noticed the "miss" as forum member LT1 had inquired about and thought of my K5 problem.
Now we have to hope that he gets some mileage out of the Vatozone OPTI. At least he has a spare OEM that may be fine. Thanks guys!
My friend found and fixed the issue which was incorrect firing order. He had plug wires swapped at the OPTI. When I was at his house we fired the car without the radiator and gave it some low RPM revs which sounded OK without a noticeable miss or such. After getting the radiator in we re-started and shut down then I left. I guess the problem was noticeable at a certain RPM and beyond which I never witnessed.
I bought a K5 once from a Ford guy who had done new cap, rotor, plugs, and wires. The thing was a dog near 40MPH and at any RPM beyond 3k. The firing order was messed up. Once I put the wires in their correct places it ran fine. Had I heard the Camaro rev up I might have had noticed the "miss" as forum member LT1 had inquired about and thought of my K5 problem.
Now we have to hope that he gets some mileage out of the Vatozone OPTI. At least he has a spare OEM that may be fine. Thanks guys!