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Thought there might be someone on here who has some experience with these.
What we have is a 91 IHC Twp. Dump/Snowplow Truck, single axle, DT-466 engine 5 speed/2 Sp transmission-axle. Truck has 1,700 engine hours, 29,000 miles. Actual and original. Keep in mind most of these miles are with a snowplow and a 3 mile straight shot is at most max and rare so the truck is accelerated and shifted a lot compared to most trucks.
Anyways it seems to have a loss of power ( we had to make a couple of hills in a lower gear than we have in the past for example) and a vibration that is engine related at RPM, not noticeable at idle. This vibration is not all the time but is becoming more so. If you press the clutch in at speed the vibration goes away as the engine comes to idle. My thought is a plugged or bad injector and it's really only running on 5 or one is week and not at full power.
Do you think a good dose of an injector cleaner would help? If so what brand would be recommended.
BTW we are located in NW Ohio and have had our share of snow here lately.
Should mention that it is a Series 4900 truck.(I think, there is no emlblem on it and I suffer from CRS after I have read it off of the door post). Do know that it will gross 43,000, don't ask how I know.

Thanks David
AKA BuckeyeBinder
 

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'Ol Builder guy
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Welcome Aboard!

Sounds like lack of use might be part of the problem. You might have an issue with critters in your fuel tank/system. Try some Howes brand in the tank and run it before you get worried. Check the CAC tubes for leaks or a broken clamp, too.

How does the oil look on the dipstick? Any grayish looking stuff (water in oil)?
 

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If u think its an injector, u can do a easy but crude test to check for dead injectors on mechanical engines. "not sure how its done on E engines" Start engine & check for leaking connections. Crack open the individual fuel-injection lines one at a time, either at the injector or at the pump. With one line cracked open at a time, listen for a change in the engine sound. The injector is bad if the sound of the engine does not change. This test will only tell you that an injector is bad, it could still have a problem like a bad spray pattern 'ie dirty. If u do the test wear some safety glasses. I would do what duke said first. Check the water seperator/ filters all that good stuff. One more thing, how long after you started using the NEW ultra low sulfer fuel, did you start having problems? My truck started out the same way, I live in wv if your not going up a hill your going down, in 2006 I could run 8 ton of gravel in 5th gear high, in early 2007 "after the fuel switch" I could not get up the same hills in 4th gear low. Now its to the point that I cant even get a full load for fear of not making it up the hill at all. I Had a similar noise in the engine,(push in the clutch noise stops) I replaced the clutch, still have the noise and the no power problem.
 

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26 tires rolling
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AN an E-model all you have to do is Unclip the harness from one injector at a time. Also while your under the valve cover look at the oil spots on the back of the injectors. they should all be putting out roughly the same amount of oil on each hit at idle..
 

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'Ol Builder guy
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When's the last time you changed fuel filters, checked for a collapsed fuel line or junk in your fuel tank.

Buddy of mines truck was running bad an it turns out there was mud in the bottom of his tank and in his fuel filters. Someone took off his fuel cap and shoved dirt in there to vandalize his truck.
 

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Dualie said:
AN an E-model all you have to do is Unclip the harness from one injector at a time. Also while your under the valve cover look at the oil spots on the back of the injectors. they should all be putting out roughly the same amount of oil on each hit at idle..
There is no need to remove the VC for this, you NEED the proper diagnostic software though (International Master Diagnostics).

You may very well have a ruptured charge air cooler hose, they are prone to failure on the back of the hose where it can rub on the engine front cover -driver's side.

The misfire sounds more like a clutch problem from your description, if it goes away when the clutch is disengaged.
 
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