2001 random mis

i have a 2001 sport 4.0 aw4. 55,000mi
it started to have a random not lasting misfire at startup sometimes.
it would throw codes for anything from 1-3 cylinder mis to random multiple mis. i replaced the coil overs, plugs checked the harness for shorts and replaced injectors on 1-3, had a very thrurough induction clean, no codes for o2 sensors. it still has a random mis every now and then and is throwing the same codes. the miss will remain for about 1-2 mins and then fade away at start. will happen when hot or cold ambient and hot or cold engine temp. when misfireing we attached a noid light to cy 1 and the light stayed lit/ did not pulse- so that means that the injector driver is bad right? the injectors all ground commonly? oh well im out of hair to pull out maybe you guys have some to lend.

Random misfires can indicate a lean condition. I'd recommending performing a comprehensive search for a major vacuum leak and also getting a fuel pressure gauge and installing it on the schrader valve on the fuel rail. Verify that your fuel pressure is around 49 psi, plus or minus 5 psi.

Good luck and let us know what you find!

You could try swapping injectors 1-3 with 4-6 to see if the code moves.

fuel pressure is good will check for vaccume leaks. thx

but a major vaccume leak would not explane why the computer dumps fuel into the cylinders that misfire. as shown by the noid light.

or if its reading lean would the computer dump fuel into the cillinders? that would make sense. thanks