injector problem?

[josh03]

So I have what I think is a common problem... and I think it's injector related: sometimes, when I start the truck, it will have a slight miss that will usually go away after about a minute or two, especially if I hold it at a high idle. Then later, once it's hot, it will develop a knock at idle that is inconsistent... Off and on, and goes away with any throttle.

Neither of these situations produce much (if any) smoke... Even the cold missing. I have seen a slight haze at hot idle, but it was very little and my guess would have something more to do with injector o-rings.

Oh, and the truck is a 1997 psd with 220k on it. Just had valve cover gaskets, glow plugs, and relay replaced along with a compression check. All looks good and it fires right up even on the coldest of mornings without hesitation. Any insight would be greatly appreciated!

[madpogue]

How old is the oil?

[josh03]

I just got the truck so I'm not sure... probably wouldn't be a bad place to start...

[BigFuel]

If the guy was vague with info then you can't be sure that he did everything kosher to this truck. It "should" be a Cali truck seeing where your located and that may be all the difference. In '97 Cali Powerstrokes where the first to use split shot injectors. The other '49 still used single shot injectors. This mostly plays a role at idle as the split shots could deliver down to nearly half the fuel and still Idle saving fuel and emissions. Really good chance the guy smoked a couple injectors and replaced them with the MUCH cheaper single shot injectors causing the kinda rough idle but fine driving. The single shot injector will over fuel at the injection pulse (compared to the split shot) and over speed the RPMs slightly to cause the normal injector to fire late causing the miss.

Change your oil so that you know when it was done. 7.3's are a totally different beast compared to Dodge and Chevy offerings when it comes to how the fueling of the engine works.