Chad Hutson

Truck is a 2004 5.4l 3v that I have recently swapped a new engine into. I purchased the truck with typical leaky timing tensioners/phaser issues but once I saw the scoring on the cam journals I decided to replace the entire engine.

Engine is a remanufactured powersource unit with a couple hundred miles. At first I had a very distinct "miss" at idle only that was fixed with a new coil on bank 2. Everything has been great but now I have a rough idle and weak acceleration that feels like it's missing. No codes (yet). i unplugged cylinder 5 injector while it was idling rough and nothing really changed so I'm wondering if it is just stuck closed or really dirty. I just don't don't want to throw parts at the engine and get no results so i am hoping that I might get some direction from people more experienced than myself. I'm close to just bringing it to a shop at this point.

Including a screenshot of live data at warm idle.

Eric Kleven

white smoke, ugh. make sure it's not lost a head gasket.

Chad Hutson

The plot thickened. I went to the tailpipe when it was missing and during the "miss" the exhaust would SUCK IN a piece of paper haha. I read that this can be a stuck exhaust valve or head gasket. Other sources say it could just be a misfire causing that.

I actually added a can of seafoam to the gas tank and it hasn't missed since. Hoping that it was just an injector.

I'll be watching coolant closely. I lost some coolant while replacing a heater core hose so I don't have a good gauge of if it is using coolant. This morning I started it and there wasn't really any smoke right at first, when I started driving there was some smoke but it went away after driving a bit. It's cold here (michigan). If i let the truck idle for 5-10 minutes it will start smoking again. I'm wondering if this is just condensation and when driving the exhaust velocity is enough to not let it really plume out, but when idling the exhaust velocity is much slower and things are allowed to condense and "steam" more.

Regardless, this is why I got the "good" warranty with the reman engine. If it's a head gasket or valve issue, it isn't my problem (to an extent).

Eric Kleven

Could well be condensation in the exhaust, any time under like 25f°. It's a lot of fun at -25f°. Could see a no-fuel hole drawing in some suction as the exhaust valve opens on the bottom of the stroke.
As far as Sea Foam goes, Marvel's Mystery Oil works much better in the gas or oil. Get some Gumout/Techron/PEA based stuff for the gas, that stuff cleans injectors out real good.