Rough hot idle?

[dunk]

'86 6.9 with Banks. New pump and injectors maybe 4k miles ago. Had some air intrusion sometimes when sitting overnight or longer. Gonna go over returns yet again soon. When I changed orings after running a few times one injector loosened, I retorqued it. Have a slight exhaust leak seems more noticeable when hot. After installing new injectors and ready to fire I noticed two copper washers missing from the old injectors, didn't see any in bores before installing new though. Double checked the injectors that were easy to get to with everything on and couldn't find them. Could be double washers on two, or maybe I dropped or lost them. Head gaskets are original so far as I know. I might be going crazy but it feels like when the engine is up to temp the idle is very slightly rough. Perfectly smooth before full temp both on and off cold advance. Puff of smoke on startup and when cold it will have a slight visible haze for a minute or so until there is some temp in it. Aside from that no smoke unless hammering down before turbo spools.

What could cause a very slight rough idle only when up to temp? Should I get more washers and go over injectors again? Could it be from air intrusion? Head gaskets? Exhaust leak messing with my mind? Something else? Truck starts easy and has good power, no issues aside from hot idle not feeling quite 100%.

 

[GunnerJ]

Slightly lean on idle? Is your lift pump mechanical? It seems to me that if it was getting tired you wouldn't be getting enough pressure to feed the ip until you got some rpms behind it, but I don't know. Maybe your timing very slightly off?

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[FORDF250HDXLT]

did you time it,if so with what equipment? are you running a water separator? did you check to see if you've got water in the fuel?

 

[FORDF250HDXLT]

yeah,you really,really,really want a water separator to protect the ip and injectors.i would make this priority #1.
without a water trap,i would imagine your warranty would be void on the ip fyi.
once you change the ip and or injectors (mostly ip) the timing is no longer set.

 

[79jasper]

Yeah, no such thing as lean or rich on a diesel.

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[dunk]

I thought even a factory fuel filter would separate water being as it flows down and back up through the element? Do you my slightly other than smooth idle is from water damage to IP? It's on my list to install additional filtration after the FSV but haven't gotten to it yet. Just changed factory filter with a WIX/NAPA when installing new pump and injectors.

As I said, timing is at 9.5* at 2000 RPM, nothing has changed since I set it. I have not checked it since installing pump a few thousand miles ago and injectors but I generally only check timing annually. Old pump and injectors ran butter smooth but has heat soak issues on hot start in summer and was way down on power compared to the new parts. Thrilled with the power, which is more like what I think it should be, but this rough idle is driving me nuts. It's so slight I sometimes think I'm going crazy. Note my exhaust is leaking slightly. Last time it leaked before I patched it up I recall it felt very slightly rough at idle but after patching it up it felt smooth again. Sounds ridiculous to me, but can an exhaust leak cause a slightly rough idle?

 

[79jasper]

It could stop some water, but the direction of flow doesn't play a big role.
It's the element itself that makes it.

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