| White Stripe | Jan 7, 2026 05:52 PM |
Lq4 Won't Idle
I have a lq4 swap with a stage 2 truck cam, drive by cable. It has the emissions plumbed and wired-no egr. I daily drove it for quite some time. The headers were cracked, and some of the wiring needed cleaned up as well as miscellaneous parts of the swap needed cleaned up. I installed a high quality fuse box, new oil cooler setup, new manifolds, reworked the exhaust a bit(which required a lot of welding/cutting/grinding),new starter, new powermaster 220 amp alternator because the winch on my truck can pull a lot of power. Overall it sat a few months with the battery disconnected. Its all together now.
The engine now doesn't want to idle. In fact it wont usually start unless I feather the throttle. On the road it hesitated under full throttle-I cleaned the maf and it accelerates great. If I put a new iac in, it will fire right up and the idle will settle fine in park and drive. But then if I shut it off for about 30 seconds and restart it, it will crank for about 5 seconds, before it begins to idle at 300 rpm then stumble its way to the target of 700. If I shift to drive it will die or almost die and then the rpms will slowly pick up to target after 5 to 10 seconds. If I let it sit until the engine is cold, it will not start or idle unless I feather the throttle. If I adjust the tb set screw to open the butterfly a little more it will then idle but will rpm dip significantly here n there. Im really confused and could use some pointers if you have them. The only code it has is a voltage code but I think thats because the alternator is putting out a little higher volts/amps | 