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Discussion Starter · #1 ·
Alright, first off, the truck has a Danville turbo, egr delete (delete pipe), turbo elbow, pcv reroute, CAI, auto, stock tune. New: water pump (March), FPR (July), batteries (Nov of 18). The only thing I’ve done in the past month to it is pull the water pump because the gasket from the water pump to the oil cooler feed pipe blew out (new water pump in March). I live in Georgia so we just went from 90s high 80s low, to around 80 high and 60s low. So not cold out yet but it is a noticeable change.

Now the problem, the truck seams to be idling rough the last week or so. It only does it at idle, as soon as I’m on the gas it runs fine. I can’t tell if the rpm bumped up just a fuzz and now it’s hit a harmonic or if it’s running rough, but it seams rough to me. The exhaust has had a slight rattle for a little while but now when it idles it’s really bad. Sounds like it might be coming from the cat but it’s hard to tell. I sure don’t recall it running like this last spring before it got so dag-gon hot. Also the exhaust has more of that lovely diesel smell too, even when the engine is warm. No codes yet and I don’t have a edge/scan tool capable of monitoring injector rates and suck. Any thoughts? Hoping to be able to fix it soon on my terms instead of when whatever it is gets worse and I don’t have a choice when I do it.


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Discussion Starter · #2 ·
Just remembered I replaced the fuel filter with the ACDelco filter about 2-3 weeks ago also


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Just remembered I replaced the fuel filter with the ACDelco filter about 2-3 weeks ago also


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i would check the filter seal and make sure that 1, you didnt accidentally double gasket the filter, and 2, the filter seal is tight (not super tight, but also not leaking). Pulling air into the system could cause a rough idle. Aside from that, i know you said you dont have a scanner, but i would see if you can find someone that does so you can get the balance and return rates. Rough idle and diesel smell could indicate a sticky injector. You could also run some biodiesel and some good additive (optilube, stanadyne, something like that) for a tank or two and see if the idle smooths out. If it does, odds are good its a sticky injector. You may also want to check rail pressure if you can get your hands on a scanner. look for actual vs commanded and record the values at idle and WOT. Lastly, a bad FPR could cause your rough idle, though i dont think it would contribute to the diesely smell. FPR issues should show themselves if you can do the rail pressure test though. I see you replaced the FPR fairly recently. was it a GM part, or a parts store part? i have heard of guys getting 2 or 3 bad FPR in a row brand new from the part store.
 

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Discussion Starter · #4 ·
I’ll see if I can get ahold of a friends snap on solstice, but it won’t be till thanksgiving. The FPR came from summit and is the Bosch one for $150 and change. As far as additive, I run Lucas fuel additive almost every tank. So ether way that’s probably not going to help and means if a injector is a problem it’s probably just about shot. I’ll look around for a scan tool also, maybe I’ll stumble across a cheap one
 

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Discussion Starter · #5 ·
Oh also, as far as the fuel filter leaking air, wouldn’t that show up more than at idle? I’m thinking more fuel draw = more vacuum = more air so I should see it all the time shouldn’t I? I’ll go out and check if the old filter has the old o-ring on it


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Oh also, as far as the fuel filter leaking air, wouldn’t that show up more than at idle? I’m thinking more fuel draw = more vacuum = more air so I should see it all the time shouldn’t I? I’ll go out and check if the old filter has the old o-ring on it


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yea, however the engine at idle has a lot less inertia so its more susceptible to failing to fire the cylinder than an engine that is cruising on the road with the weight of the truck driving it through any missfire events. Its not uncommon for trucks with leaking filter heads to stall at idle but drive fine, or stall at idle and occasionally throw a gross fuel leak code, but they "run fine" on the highway.
 

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Discussion Starter · #7 ·
yea, however the engine at idle has a lot less inertia so its more susceptible to failing to fire the cylinder than an engine that is cruising on the road with the weight of the truck driving it through any missfire events. Its not uncommon for trucks with leaking filter heads to stall at idle but drive fine, or stall at idle and occasionally throw a gross fuel leak code, but they "run fine" on the highway.


Yeah that makes sense. Well I at least didn’t double up the o-rings. Just checked the old filter and it still has one so I’m good there at least.


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Yeah that makes sense. Well I at least didn’t double up the o-rings. Just checked the old filter and it still has one so I’m good there at least.


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maybe give it an 1/8 or 1/4 turn tighter and see if that helps? ive had filters leak around the gasket before that seemed tight enough.
 

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Discussion Starter · #9 ·
maybe give it an 1/8 or 1/4 turn tighter and see if that helps? ive had filters leak around the gasket before that seemed tight enough.


Hey I’ll give it a shot, that’s free to try. I’ll do that and see if it works when I go to work tomorrow


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Hey I’ll give it a shot, that’s free to try. I’ll do that and see if it works when I go to work tomorrow


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i generally prefer to rule out the cheap / free stuff first before throwing parts at the problem whenever possible.
 

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Discussion Starter · #11 ·
Well cranking the filter a little tighter didn’t help. My body is going to see about shipping me his scan tool in case I don’t find one. If it’s a leaky injector does it ever cause a puff of smoke at start up I could look for? Haven’t noticed one yet but I keep forgetting to which the mirror.


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Well cranking the filter a little tighter didn’t help. My body is going to see about shipping me his scan tool in case I don’t find one. If it’s a leaky injector does it ever cause a puff of smoke at start up I could look for? Haven’t noticed one yet but I keep forgetting to which the mirror.


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a sticky injector will hang open and can spray fuel in any of the 4 strokes, so you would be spraying fuel into the cylinder on the down stroke washing the oil off the walls, and you would be spraying fuel into the cylinder on the up stroke out the exhaust. This is where you get your white smoke from, its unburned diesel fuel blowing out the tail pipe. This differs from black smoke, which is fuel that has been burned, but not in the presence of sufficient oxygen to completely react with all of the fuel.
 

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Discussion Starter · #13 ·
Well to rule out the exhaust I just unhooked it at the down pipe and low and behold it sure seams to be gone now. I haven’t drove it yet because it started poring rain before I finished but I think it must just be the cat (or whatever is loose) loosened up enough it was hitting a harmonic. Boy the wife is enjoying her guess being right... lol

So needless to say I used it as a excuse to have a 4 inch mbrp on the way now so once I get it on I’ll report back but I think I got it fixed a lot cheaper/easier than I was thinking it would be


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Couple of other low hanging fruit ideas would be to do a bottle test (search will explain) and replace FPRV (not same as FPR).
 

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Discussion Starter · #15 ·
Couple of other low hanging fruit ideas would be to do a bottle test (search will explain) and replace FPRV (not same as FPR).


Thanks. I hadn’t seen that one yet. I think the exhaust will fix it but that’s easy enough to try anyway just to check to state of the FPVR.


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