LS3 misfire

[1985olds]

Good afternoon,

I’ve got a g body with an ls3, tsp cam, ported heads and TREMEC magnum. It’s run by a Holley terminator x max. I drove the car 35 miles this morning with no issue and on my way home it started to misfire. It’s a single misfire when cruising. It’s random and without rhyme or reason. The tach will drop when it misfires. Cruising along at 65-75 mph and it will just hit once and then resume as normal. Smooth under acceleration. Any ideas? Thank you.

[joeko23]

Are you able to read codes? If you don’t have a tool, you can get yourself an OBD dongle then download an app on your iPhone (car scanner elm). If you have an android (torque) and read the diagnostic codes. Could be something as simple as a cracked/broken wire or terminal or connector.

[1985olds]

Are you able to read codes? If you don’t have a tool, you can get yourself an OBD dongle then download an app on your iPhone (car scanner elm). If you have an android (torque) and read the diagnostic codes. Could be something as simple as a cracked/broken wire or terminal or connector.

i have a Holley terminator x, no obd port. The malfunction lights on the Holley don’t show anything. I’ve been checking the wiring harness where I can get to it and haven’t found anything yet. My thought is that based on the rpm drop on the tach that it could be a crank sensor.

[andrewb70]

i have a Holley terminator x, no obd port. The malfunction lights on the Holley don’t show anything. I’ve been checking the wiring harness where I can get to it and haven’t found anything yet. My thought is that based on the rpm drop on the tach that it could be a crank sensor.

Are any of the Terminator X ECU LEDs turning red? If I can help with the tuning, email me: projectgattago at gmail dot com

Andrew

[1985olds]

Are any of the Terminator X ECU LEDs turning red? If I can help with the tuning, email me: projectgattago at gmail dot com

Andrew

no lights changing to red. I checked idling and while driving. I might have to take you up on that. Im going to change the crank sensor because I have a spare and if it doesn’t help I’m going to data log.

[streetk14]

Not to knock on Holley, but this was a big motivator for me going with a factory E38. Having real diagnostic capability when something goes wrong.

[ORBandit]

^^^Completely agree. I run a Dominator, and problem solving is a MF. Best advice, pull the plugs. There are some primitive tools built into the software so you can monitor crank and cam sensors, they also can cause misfires. Other than that, likely plugs or wires. Cheap plug wires are typically the number 1. I put mine away for the winter one time, (less than 1000miles on it) took it off the lift in the spring, nasty misfires. Tried everything, including plugs, fuel filter, had injectors cleaned, swapped sensors, etc. After all said and done, wires....

[andrewb70]

^^^Completely agree. I run a Dominator, and problem solving is a MF. Best advice, pull the plugs. There are some primitive tools built into the software so you can monitor crank and cam sensors, they also can cause misfires. Other than that, likely plugs or wires. Cheap plug wires are typically the number 1. I put mine away for the winter one time, (less than 1000miles on it) took it off the lift in the spring, nasty misfires. Tried everything, including plugs, fuel filter, had injectors cleaned, swapped sensors, etc. After all said and done, wires....

The Holley EFI systems provide a vast array of data that one can monitor. All these data offer clues as to what might be happening.

Andrew

[1985olds]

^^^Completely agree. I run a Dominator, and problem solving is a MF. Best advice, pull the plugs. There are some primitive tools built into the software so you can monitor crank and cam sensors, they also can cause misfires. Other than that, likely plugs or wires. Cheap plug wires are typically the number 1. I put mine away for the winter one time, (less than 1000miles on it) took it off the lift in the spring, nasty misfires. Tried everything, including plugs, fuel filter, had injectors cleaned, swapped sensors, etc. After all said and done, wires....

The wires are not new but not old and gm. I’ll ohm test them. It’s such a weird misfire, if it was any lighter it probably wouldn’t be noticeable.

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The Holley EFI systems provide a vast array of data that one can monitor. All these data offer clues as to what might be happening.

Andrew

I really need to get more familiar with all of the capabilities in the holley

[andrewb70]

The wires are not new but not old and gm. I’ll ohm test them. It’s such a weird misfire, if it was any lighter it probably wouldn’t be noticeable.

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I really need to get more familiar with all of the capabilities in the holley

Make sure the two grounds at the back of the heads are tight.

Andrew

[1985olds]

Make sure the two grounds at the back of the heads are tight.

Andrew

will do! Thank you

[csouth]

How long ago did you purchase this? I know within the last yr or so, they have been have some very common harness issues. Some guys are buying the ECU and getting aftermarket harnesses made for Holley systems.

[1985olds]

How long ago did you purchase this? I know within the last yr or so, they have been have some very common harness issues. Some guys are buying the ECU and getting aftermarket harnesses made for Holley systems.

the Holley I have is about 3 years old

[andrewb70]

the Holley I have is about 3 years old

Email me. I can log in using TeamViewer software and see what's going on in real time. You'll need a Windows laptop and the USB to CAN cable, Holley part number 558-443. Email: projectgattago at Gmail dot com

Andrew

[ORBandit]

The Holley EFI systems provide a vast array of data that one can monitor. All these data offer clues as to what might be happening.

Andrew

Agree. What I more or less stated. That said, troubleshooting is terrible compared to GM. After using HPT for a 15yrs, switching to Holley has its benefits, but their are clear downsides. This being one of them.