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Erratic Idle ICP Fluctuation
I just recently replaced the head gaskets and put in arp studs in my truck, heads were machined and pressure tested. It has about 85000 miles. Everything went great with the install. The truck is tuned with bolt safe looney tune I never retuned after the studs. When I first started driving the truck after the install I started getting an erratic idle when the truck is warm. When the truck first starts cold, it idles great smooth and feels like its hitting on every cylinder. Once warm the idle starts getting a little choppy and then it feels like its dropping a cylinder out. The cylinder wont stay dead, it comes and goes..
I have checked all push rods and hot or cold at any throttle there is no misfire, it runs great. Only when you drop back down to idle it will start running funny. I have a livewire and a scanguage. With the scanguage you can watch the icp and the ipr. After a cold start I can watch the ICP start to drop and when it gets around 600psi the cylinder or cylinders drop out, and you can visible watch the computer raise ICP and pull the cylinder back up to a normal idle and then from there on its a constant balance of icp drop off erratic idle then the pcm pull icp up and cylinder back in.
I do not have any codes and when the injectors were out I checked the spool valves and the were varnish free. There is no stiction at cold start. I have installed the blue spring kit as well.
I have replaced the standpipe, dummy plugs and stc previously before head studs due to a long hot start which took care of that issue. Also has fresh rotella t6 and motorcraft oil filter. Fuel filters were changed within the last 4000 miles
Any help appreciated. It seems oil related or oil side injector related. Also, this happens on stuck or tuned truck.
FX-4 Manual Trans
Leveled, American Racing Mojaves Nitto Terra Grapplers
Last edited by reilly828282; 07-24-2013 at 05:37 AM.