Rough idle / miss, runs fine off idle

[JCockerill]

Just noticed a rough idle feels like a miss at idle, once u rev it up or load it, runs fine. Truck has 76k on it. I also get the auto fast idle lope if that's related, also once in a while i will have a long cold start crank, it will hicup a few times then start. Poor mpg (10mpg) No engine light. I have fresh oil and filters in it. Fca or injector? I have to check for the ac wire rub through but figured I would get other ideas before I dig in. Funny thing is it runs great once you are going down the road or towing

 

[cerberusiam]

Most likely injectors with the bad fuel mileage.

 

[JCockerill]

Bad injectors with 76k normal? Wouldn't it be rough all the way up rpm? What's best way to test them?

 

[cerberusiam]

Won't always be rough off idle, just depends on where the issue is. The 10 mpg is not a good sign.

Cylinder contribution and kill test with rpm drop using a scanner is an easy start. Otherwise, you probably have to pull them and send them somewhere to be tested.

 

[JCockerill]

10-4 I'll test um and report back

 

[rashwor]

I had a similar issue with mine a couple of months ago; rough idle with blue smoke. Would only occur randomly with cold starts. Changed the filter and poured in a jug of PowerService (white bottle winter formula). Seems to have cleared it up for now, knock on wood... my suspicion on mine was injectors too, simply due to my mileage.

I am not bragging, but I am slightly better off in getting my money out of my original injectors since I am at 279,000 miles.

 

[fkovalski]

10-4 I'll test um and report back

Any news or updates?

 

[JCockerill]

I tested them with snap on scan tool and did balance test, checked out ok, added some instructor cleaner to tank and so far so good, I found a tsb that referred to cold weather idle ing causing injector misses, so maybe that was it

 

[cerberusiam]

Yeah, cold weather idling and light use raises havoc with gumming up the injectors. A good injector cleaning and constant additives is almost mandatory.

 

[DonFitzwater]

I pulled mine out of my 06 at one point and cleaned the nozzles with some Evinrude engine tuner(powerful decarbon) and a toothbrush. Really improved startup and idle quality.