LS1 missing

[Jimr]

Have never posted but have followed for some time. I have a 68c10 and have added a 1999 Camaro LS1, 4L60E and kept the same wiring and computer. It has been programed but not when driving. I have one problem. It misses at idle or slow speeds from time to time. I moved a new fuel tank to under the bed, new outside fuel rail pump and filter, new fuel lines. I changed the injectors but thought the new ones might not be good so I cleaned the old ones and replaced them. Each time I change something I think its better but it starts again after a few miles. Could it be fuel rail dirt? How can you clean it? What other things could be a problem?

[AussieinNC]

Is it possible for you to pull OBD codes stored in the ECM?

Did you retain the OBD 2 diagnostic port?

These used to have an issue with bad coils that would short out as they started to warm up...

Also, check the ground cables...battery to engine, engine to chassis, engine to cab...

[jjzepplin]

I have that same motor. I drove it before I swapped it so I know it should run OK. Was this a tested motor for you as well?

[Jimr]

Do have the OMD port. Had codes checked for first start and once after more was added. Not checked since I started driving.

I will check grounds and coils and have OMD codes checked.

I took the LS1 from the Camaro after it was wrecked and running good.

[ls1nova71]

Have you started with the simple things? Like checking the plugs and wires?

[jjzepplin]

Oh and in case no one has hit you up yet, WELCOME to the site!

[Jimr]

I installed new plugs but will check the wires. THANKS

[jjzepplin]

You should be able to check the coils with a standard timing light, right?

[AussieinNC]

Yes...just place the pickup of the timing light on each lead to check for it firing....the light will flash is coil fires (make sure the power leads for the light are connected to battery and ground)

[prodjay10]

New plugs when you finished the swap? They are easy to crack during. Also cables are easily damaged.

It helps to have a scan tool with live data to tell you which cylinders are missing. You can swap plugs, cables, coils around to isolate
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[jessemthompson]

I would go back to the basics. Disconnect a plug wire while it’s running, if it changes the way it runs, you know that cylinder is good. When you pull the plug wire and it doesn’t change the way it runs, you have your cylinder that’s missing. Then you narrow down the problem. Coil, plug, plug wire or the injector.

[Jimr]

Thanks for all the info. I will start checking out the firing. I talked to my good restorer friend and I pointed out that the engine fails while driving slow or sometime slowing down and stopping. I put a new tank between the frame under the bed. I
Installed a high pressure pump but thought it had to be below the tank. Because of that I put the pump just behind the cab in the frame. Thought from my friend is that the pump might not be able to pull that far from the tank. He said these high pressure pumps push but don't pull much. He has always put the pump close to the tank not concerned about its height from the tank. YOUR THOGHTS and MORE IDEAS?

[prodjay10]

If you think its fuel pressure related, get a fuel pressure tester and put it on the rail. It's easy to check on these engines. You can even rent the tool.

[prodjay10]

Just want to point out you want to get a bad misfire fixed before driving to much. Unburned fuel will thin out your oil and cause excess wear.

Also replace oil as soon as the misfire is fixed for that same reason.
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[Jimr]

Thanks, I will check the pressure and make sure I change the oil and filter. It took me two years to get this done including two knees and a move to retirement. It will be my driver.