2000 Cat C15 Smokes and Skips

My 2000 CAT C15 smokes white and skips. It smokes white just on start up then clears up, but skips continually while running. The only side effects I've noticed to the symptoms is a loss in fuel mileage.


The Back Ground info...The smoking and skipping started suddenly, as soon as it started I took my truck to a reputable licensed garage. The mechanic there ran three injector cut out tests. 1st Test injector #4 Failed. 2nd and #rd Tests all injectors passed.Then they did an engine coolant pressure test, the bottle test, and that passed as well. I decided to run the truck for a trip (2000 miles). During that trip I calculated my fuel mileage and it dropped from 6.2 to 4.1 MPG. The whole trip the truck continued to smoke on start up and skip continually.


When I got back from that trip I brought the truck back to the same garage and they ran the injector cut out test three more times, and all injectors passed all three times. When they removed the manifold they found that injector #4 was smoking so, I had it replaced. That didn't solve the problem so I had them replace all of my injector o-rings, 5 of 6 were broken or cracked.Hoping that had fixed the problem I brought the truck home, Approx. 30 kms. However the truck was still skipping and smoking on start up, but the skipping is twice as rough as before.


The next day I took my truck in for it's scheduled oil change at a different reputable licensed garage. I asked them if they could run the injector cut out test while I was there, and they did. Once again All injectors passed, but It's still skipping and smoking. After I left there I called a licensed mechanic that I know and he said that he would come over in the am to run the injector cut out tests while the truck was cold. I left the truck outside overnight in -20 degree Celsius.When he ran the test injector #4 failed all 3 times(the injector I just had replaced).


I brought the truck back to the garage where I had the injector replaced and told them the proceedings. They decided they wanted to re-run the tests themselves, and tried multiple different ways they knew how to test the injectors, and they all passed AGAIN. Their Diagnosis was one of two things. 1) A blown Head Gasket. 2) A Bad Liner between cylinders 4 and 5, and both will require an inframe to repair.


I asked them if it was ok to run the truck another 2000 miles and they okayed it, but said I shouldn't run it much longer than that. I am just getting home from that trip now, and I'm not seeing any signs, other than skipping and smoking on start up and loss of fuel mileage, that their diagnosis is correct. The truck seems to be running fine... No loss of power and I'm not leaking any fluids.


your input is greatly appreciated. I really hope you have some suggestions of other things to check out, or if you think that the inframe is necessary.


Eagerly Anticipating your reply.... Phantome 379