99 f250 7.3l with 200,000 miles. cyl 3 and 4 are dead and has alot of blue smoke.
I ran the injector buzz test and all buzzed and sounded good. I ran the cylinder contribution test and cylinder 3 failed. I replaced the cyl 3 injector, and test drove it. The truck still had a missfire. So i ran the buzz test again and code p1668 (IDM EF circuit failure) came up. A few minutes later i ran the buzz test again and the code would not come back. I ran the contribution test again, and cylinder 3 and 4 failed. I guess i am leaning twards the IDM but any known problems or advice would be great. Thanks in advance.