Low fuel mileage and rough idle
 

Like the title says guys I seem to have a couple of problems here. When the truck is first started in the morning the truck seems to idle fine an the rpms stay preaty well steddy, but after its up to operating temp it seems to have a slight a miss or a hiccup to it:argh: and the fuel mileage has just started to start to go down hill for some reason. Oh an also when the truck has set for say a day an when I go to start it it seems to have to crank longer than usual, but after its been run it doesnt have the problem anymore. For the rough Idle Ive check for codes and have none that pretains to the vp an I just replaced the vp bout 5 months ago with one from Industrial Injection and it sees a constant 14-17 psi fuel pressure from the airdog. Ive also replaced the apps sensor too. So my question is what would be causing this thing to have a rough idle? Could it be the injectors needing pop pressure adjusted, air in the fuel lines, fuel lines sucking air somewhere, maybe a sensor, or possibly the overflow valve at the vp?? Im to the point that Im bout ready to set a 20lb box of dynamite under it an watch it go boom. So any help or suggestions would greatly be appreciated.

Thanks Andrew

Sounds like injector issue. You can crack your fuel lines to check for air. Might need to pull the injectors and get them tested like you said. Id ask when was the last time you got your valves adjusted but it sounds more like an injector problem. Dont use dynamite. Everything can be fixed:c:

Yeah I adjusted the valves probably 3 weeks ago. I set them at .008 intake and.018 exhaust.

Is your truck smoking more then normal?

No not really just when I have the Smarty turned up, but my cousin told me that he noticed it blew just alittle bit of blue smoke. Which is why I was wondering bout the injectors maybe one isnt seated properly an is letting oil come down the side of the injector.

sounds like you have an injector missfire. my truck does the same thing, and thats what i narrowed it down to.

Ok so I just went an bleed my fuel injectors all except for no. 2 and the truck seem to run preaty smooth for the most part. When it got up to around 170 degrees it started to have the same ol miss/hiccup to it as before. So Im leaning to maybe a sticky injector/injector missfire. Anyone else have any suggestions??? Thanks again for the info and help guys:tu:

So Ive been thinking an was just wondering but when u bleed the injectors are they supposed to have alittle foam coming out or just pure fuel with no foam?

yea your gonna have some bubbling since your gonna have air in the lines as long as you have fuel to 1,3,4 it should start itll be ruff for a little bit but it should smooth out.

So just alittle update today when I was sitting in the parking lot I raised the rpms slowly and noticed that the truck had some vibration to it. Now I know the mighty Cummins shakes and any diesel for that fact but this was not motor vibration. It seemed to happen between 1500-1800 rpms give or take, but when I revved it to 2000 an above it smoothed out. What does this sound like to yall? Maybe a stuck injector, air in the lines, or something else? I stopped by the Kenworth on the way home and ordered the o-rings for the connector tubes, o-rings for the injectors, and the copper washer for the injector. Do yall think this will help or should I look into something else?? Again the vp's been replaced bout 5 months ago and no codes pretaining to vp an it's recieving anywhere from 15-18 psi from the airdog. Im also considering replacing the fuel lines to an fromt the airdog also. Again thanks for all the info and help guys:tu:

like i said, your symptoms sound like an injector missfire. they have to be replaced.

You can go and get your injectors pop tested, if you had an stuck injector you would proabaly notice it, my truck smoked like a freight train. If you have em out cant hurt to test em...

$150 bucks... And there probably going to need to be rebuilt. Which isn't worth it. Better off getting a new set something like rv275's a little more power, and better mpg.


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My truck also has a studded/misfire at idle only.It is bone stock has new lift pump,no smoke,it did throw crankshaft sensor code when check engine light came on but after I checked codes while driving check engine light went off and it has plenty of power but I'm only getting 400 to a tank of fuel.Any suggestions?

My truck vibrated alot right around 1800 rpm and it turned out to be the motor mounts

Mine is a slight miss/stutter at idle 900 RPM's could it be catiltic convertor? It does not smoke and seems to not be losing any power.The truck is stock and 16 years old.I do not know if valves have been adjusted? I did put a new lift pump on last week.

How long was your lift put bad for meaning how long has it not been giveing enough fuel pressure to your vp. If it has been starving your vp it could have damadged the vp but its super easy and not expensive to check the valves vp=1000$

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I would say also put a straight pipe on it ...it helps with egts mpg and ofcourse sound :tttt:

I parked it as soon as I caught it.1 day is what I got figured.Im hoping it is not VP because my cousin has same truck as me but its a gray shortbed with 140,000 and his lift pump went out and it did get injector pump! I'm going to keep my eye on it for now but there is a local guy who I know that did a Ppump swap and has a HO VP with 20,000 miles that was feed those miles with a FASS and I can buy his VP for $700.

Is your truck a H.O if not you will not be able to use it ...those pumps have more pressure and less volume so it will hurt the performence of a S.O truck quite a bit and for 200-300 more you can have a the right pump from thoroughbred diesel

I'm glade you told me that Thoroughbred is about a hour and a half from my front door to there shop.Im hoping its not VP at all I bought the truck from a family farming friend and he is 72 years old and is very honest person.Thats the reason I bought the truck from him.I really wanted one that already had all the Hi-Performance stuff done to it but the truck is bone stock and has 202,000 miles on it now and the only things that are not original are tires,tie rods,Lift Pump and radio.The VP is original and has outlived 4 Lift Pumps(according to old owner he put on 3)and I paid cash for truck and my money is low right now or I would've put a FASS or Airdog on instead of the Air-Tex that Advance Auto made up because of lifetime Warranty.Maybe I will get lucky and not have to buy a VP! I don't have fuel in oil and the truck does not smoke so I don't think it's a injector that is causing the stutter/miss(at certain times)at idle? I do appreciate all the help I can get.There is a guy on local Craigslist that has a 5'inch exhaust for $100 Whats do you think about it? I'm thinking maybe the catalytic converter is bad its 17 years old

A 5 inch for 100$ i would scoop it up quick and you can get the same lift pump i have for 375 from blue chip and it is a awesome pump the raptor 150gph and big line kit and if the vp is that old i would just about put money on it being the vp

I can buy a used Raptor 150 for $100 and the guy with the exhaust is a being a jerk(seems like everything on Craigslist is always a pain anymore)and has went from $100 OBO to well I got a Duramax and I'm just going to put the pipe on there if I don't get $150 and I will need the pipe that goes from the turbo to the exhaust so I know what that means is another foot of pipe I will have to buy.

Yea i would look at the pump for sure look on ebay you can get a full exhaust system pretty cheap

I replaced crankshaft position sensor&everything was fine my cousin gave me his stock exhaust and it worked fine until i noticed a hole around the hanger about 2 weeks ago.Im going to take your advice and buy straight pipe this time im on a budget&try to save where i can i thought i had a bad injector a while back but i did crack open the injector lines and looked on mopar mans site and he says injectors should go a million miles&has a friend on his site that has over that on his truck with the same block (the notorious)#53 as mine.because of my budget issues i went to harbor freight and bought a $20 gauge and put it directly into fuel filter housing to check fuel pressure after i got (advance made up the old lift pump the last owner of my truck put on when it stop working&luckly i caught it before it got the VP) lift pump on and im getting between 12-16 PSI but having long crank times when it is drove for a hour or so&is starting fine after sitting overnight dose anyone have any suggestions on this? Any help is appreciated&Thanks for all the helpful advice.

any one looking for a good used set 275 had them in my truck for a year, We where getting smoke in our RV as we where going down the road, so we went back to factory..