My 97 SD has a weak cylinder that comes and goes. It always has a miss on cold start with accompanied blue huffing from the stack that goes away quickly on warm days and longer on cold ones. Glow plugs are all good and the truck starts very easily on very cold days. It was 5 here the other day and it started right up with no block heater. The miss will return off and on while driving, MOST of the time the miss will be there when I get back on the throttle after coasting down a long hill or slowing down for some other reason. After a couple seconds back on the throttle it goes away. Sometimes it will begin to miss at a steady highway speed. I can let off the throttlle and mash it and the miss will go away but if I dont do anything the miss will stay. It wil never miss while knocking around town. This is not a complete miss like a totaly dead cylinder, I have had that before, but a half dead one. I assume it cant be a mechanical problem like low comression since it comes and goes? Compression checks OK on all 8. My mechanic at work has a shop at home and works on vehicles including some Power Stroke work but he is by no means an expert. He does have a gadget that plugs in under the dash and runs the motor through some sort of diagnstic test called cylinder balance or contribution and it said that cyinders number 2 and 8 were weak. After replacing those injectors with rebuilds the motor now has much more power but the still has the miss that comes and goes. He thinks an injector problem but doesnt know how to narrow it down. Hate to buy 6 more reman injectors to get rid of one bad one (cheapo here, LOL) Any ideas? As always thanks in advance.

 

You can start with cleaning the FPR screen & maybe a new filter ,,,Have Him monitor ICP pressure's & maybe EOT as it compares to ambient air temp while driving it at the speed that it misses the most ...


Also , look at the ICP sensor itself ,, it maybe leaking oil from it.... Do one test at a time , so you know what fixed it ....

 

Just cleaned the screen and will try a new filter. Thanks