Read a bunch of other posts similar to mine but couldn’t find an answer. I have a 1998 hijet (twin cam) (fuel injected). When I first turn the truck on it idles fine, driving is also fine. But after it’s warmed up and i come to a stop light the truck has a roughness only at idle. Right when i tap my foot on the gas it’s fine again. I have done spark plugs, ignition coils, fuel filter, and vacuum lines. And just to be sure there was no vacuum leak at all I used a smoke machine and no smoke came out from anywhere. So I am at a loss of where to go from here. I ran seafoam in the gas tank as well as the one that goes into the throttle body to clean the top half the engine. After the seafoam it seems to be slightly better but nowhere near as good as the idle should be.
