I have 2 issues with my truck. Some times my idle lopes from 800 to 900 rpm. This issue seems like not a big deal but maybe points to the other issue of a miss at idle and at speed.The lope issue seems to be only while the truck is getting up to temperature and it is inconsistent. The second issue is the truck develops a miss as it warms. I have isolated it to cyc 3 and 4 by using a snap on code reader /scanner. My son thinks I have a couple of leaking injectors or possibly crossover tubes. Truck gets good mileage 14 in town and over 20 on the road at 70.Truck information ; 180 k miles 3/4 ton 4x4 5 speed. Fairly new injection pump 20 pounds pressure at idle.Some black smoke at start up.

Question is any way to diagnose further without removing injectors and if its injectors should I repair 2 , clean and repair all 6 .....Thoughts suggestions ideas are welcome.I am not really a mechanic but can read and figure out things slowly. My son is a mechanic with 6 plus years experience and does diesels for a living working on over the road big rigs. He helps me when I get stuck/ over whelmed.  

Valve lash might be too tight or lose double check that. It can cause lopey idle. Then I would replace the injectors. After about 100k miles the injectors start losing pop pressure and spray gets rather crappy. 14 MPG in town is low. I typically can hit at least 18-22 MPG in town. I would look into the injectors and replace them.

So I can do the overhead valve lash adjustment.

Can you clean the injectors and have the pop pressure reset like on a Mercedes diesel or do I have to buy new or rebuilt injectors ?

If I have to buy new what do I buy ? brand  size ?

I got my injection pump from Gomers out of Missoula and was very happy with their service

I am happy with how the truck runs with the standard injectors and very happy with my overall Fuel mileage. Trucks gets a solid 21 to 22 driving 75 Helena to Seattle and back.

How do you get 18-22 in town ?

THANKS for your response

John

Yeah the can be pop tested but most likely the nozzle and little are worn so replace is the typical solution. Most of us buy injectors from DAP or Diesel Auto Power. I'm getting ready to replace my 7 x 0.0085 injectors with a fresh set. This set I'm going for 310 to 315 bar pop pressure.

 

Common MPG Better is the RV275 injector. The other half of the MPG is having a tuner to advance timing. Stock tune is rather retarded in timing

So are you talking replace the whole injector or just the nozel ?

Usually easier to buy a set of injectors and return your stock ones as a core after they are changed out. 

If I understand correctly idle is controlled by the ECM so I would check for codes and then ac noise (vac) from alternator, should be less then .05vac .03 is better and there is a ground mod that will cut it in half to about. 015vac. Very important on these trucks not to have ac noise and having all good grounds with batteries. 

If you're not doing anything crazy then rv275 is the way to go and most time there is no core charge on new injectors. You can probably go up to 60-75hp injectors on hx35 without issues but it would be better to have a tuner at this point. Qwadzila is the one for vp44 trucks hands down. 

The only time I would pay to check pop pressure and make sure they flow good is if it's something you want to keep, like I have 7x10 vco from dap set at 320 bar now, and pretty happy with the set up i got. So in 100k or when I feel nassasary I'll have these checked out and put them back in. If yours are original with more than 100k I would just send them in as a core, but sounds like they may be not original as they blow black smoke on start up.

How high can you get boost, what turbo you got, any gauges on truck, tuners, etc?