charger21

I have a misfire on No. 1 cylinder. This problem happened after a LS6 ported intake and ported T/B install. I have spark and injector pulse. I tried a new spark plug, new plug wire, new coil, new injector. Lastly, did a compression test and I have compression. Any ideas? Thanks

C5Wolfe

Might check your Intake gaskets, Maybe a bad gasket causing a loss of Vacume?

robert miller

Maybe above but also look at a bad coil.still chg out one other coil in that one,s place.

LoneStarFRC

In addition to what Robert said, I'm wondering is there any "ticking" going on? Pull your valve cover and check both rockers and the valvesprings too.

Trace your fuel injector wiring harness where it goes around the fuel rail stop hardware and into the rear behind the intake to see if it's chaffing or has rubbed through. It could be making an intermittent connection.

baxsom

i had a bad spark and tried everything but turned out i only had the wire clicked on the coil once and not twice. i pushed harder got another click and the misfire went away.

charger21

Tried all of the above, still have misfire

madmatt9471

So you:
(1) swapped coils
(2) Checked for leak in intake (with WD-40 or water etc. while running to see if there is a change)
(3) New Plug
(4) Used a different wire (swapped from another plug)
(5) Checked wire connections
(6) Checked cylinder pressure (with compression tester I assume)

At this point you "MUST" thoroughly check the wire harness for the coils all the way back by the firewall and the Injectors - it has happened in the past that others have pinched the wire going to one of these!

Plus make sure you coil connection (White weather pack for the coils) is fully engaged for the coils!

Let us know! what you find - it sounds like a simple solution like a pinched wire!

Thanks,Matt

LoneStarFRC

Added 6 & 7. He says he has done this also. (See post#4)

He may even have an individual injector going south too.

charger21

Everything above, including compression test was done. I will inspect harness more closely and hopefully it is a simple fix.

charger21

Someone told me that spraying around the intake with WD-40 is a good way to check the intake, BUT, not 100% effective. So, the intake is coming off.

dougbfresh

Swap injectors with another cylinder FIRST. One clogged injector can do this, if the misfire follows the injector you'll know.

charger21

Already swapped injector with a new one

crainholio

Did you install new intake gaskets, and torque the intake bolts to spec in the 2-step process?

Common causes of problems after intake manifold installation are usually re-use of old/flattened intake gaskets and/or improper tightening of the bolts.

robert miller

with this also...

charger21

Yes, I used all new GM gaskets, and torqued bolts during the 2 step process. I wonder if it could be the ported intake itself. I bought it used from a very reputable dealer here on the forum, and they did the porting. I am pulling the intake today. Thanks for everyone's help so far. Keep the ideas coming.

madmatt9471

Looking forward to seeing your findings! Keep us posted!

I wonder if your "COIL" itself took a dump!

Thanks,Matt

charger21

Well, problem solved. I swapped intakes and put my old LS1 intake back on. No misfire, runs perfect. So, I got to looking at the ported LS6 intake I bought and it looks like they took to much material off around the injector hole on No. 1 cylinder. To double check myself, and with the help of a great friend, we reinstalled the ported intake again and got the same No. 1 misfire. The injector hole had noticeably more material removed than the other injector holes. I bought the intake during the winter time from Jeremy Formato who is a Premium Supporting Vendor, thank God. I will call him tomorrow in hopes he has another intake. Thanks again for everybody's help!

madmatt9471

Excellent catch and it's gonna be good info for others too!

Thanks,Matt

robert miller

Also glad the OP got the fix on the car..