Engine/Transmission (1994 - 1998) 12-valve Engine Miss Poll (please read before voting)

[Vaughn MacKenzie]

I am curious to find out approximately what percentage of guys have experienced an engine miss with their p-pump 12-valve. In particular a steady miss where it's one certain cylinder not putting out as much power as the others, resulting in a noticeable shudder at idle or under part load. It may miss at idle, at part load, at certain RPM, or all the above. . . but this poll is to focus on the steady single-cylinder miss problem guys often have.



Here's how to answer the poll:



If you only have the typical erratic cold-startup miss or have touchy/erratic GSK (quick stutter or bark) check "My 12-valve runs smoothly. "



If your miss doesn't fall under the description I gave above and is occasional, random (isn't any particular cylinder) or may have to do with a radical pump/injector setup then check the last option.



Please don't vote if your engine didn't come from the factory with a p-pump.



Thanks all,



Vaughn

 

[Cooker]

Should I vote twice since I have two



Did your truck you new pump Vaughn, did that not solve the problem?

 

[BigPapa]

Vaughn,



I voted:



I have (or had) a difficult or unresolvable steady miss



because I have had for the past 80K-100K miles a miss accompanied by a "knock" that I have tried to diagnose. The truck has 217K miles on her. The miss occurs noticeably at @1600-1800 rpm. It is so noticeable at that point that the whole truck shakes and if I try to cruise at that point it feels like I have a tire out of balance or a bent wheel. It seems to idle fine.



I have changed the following:

• Injectors (installed used, cleaned and tested 215's)
  
• Lift Pump
  
• Overflow valve
  
• Fuel lines
  
• Adjusted Valves
  
• Oil analysis to rule out engine problems
  

A local pump shop has told me that the rack in my IP is probably sticking just enough at one point to cause what he called an "irregular exhaust pulse". I have a different pump on-hand that I am going to swap out and have the timing advanced when I get the funds. It is a 175 HP pump from a manual transmission truck. It has 181 DV's installed and I will be putting my home-ground #10 plate in it. I need to get a GSK for it and then the pump shop is going to bench tune it and I'm going to swap it out. It has @120K miles on it and the original owner told me he had no problems with it. He went to a 215. What I have now is a stock 160 pump with my #10 plate in it and the star wheel turned. I hope this will get rid of my "miss".



Scott

 

[Johnstra]

Kind of hard to answer...



FWIW, I voted "My 12v has always run smoothly", even though I feel my engine probably has some slight variation between cylinder firing power. My idle is set at about 850-875 and the engine shudders slightly at idle, but not bad at all. I have posted that I have a whump whump whump sound under heavy load at times, but I don't call this a miss either.



-john

 

[Grizzly]

Can I vote for my 95 (previous) and my 05 (current)?

 

[Cooker]

Can I vote for my 95 (previous) and my 05 (current)?

Is you 05 a 12v

 

[supersonic]

I voted for option 4. Both of mine are BOMBS related. 120 line fat nozzles and radical timing can make these do all kinds of crazy things

 

[Vaughn MacKenzie]

Thanks for voting all. The reason I posted this is because I've been fighting a miss for a year on my truck and from various posts on here and NW Bombers I've had quite a few email & PM me saying they've had similar challenges. So I was trying to get a feel for how prevalent this problem is. Looks like 77% say they're running smooth so that is good to hear.



In my experience getting familiar with 12-valves it does seem they are more temperamental and susceptable to developing a miss than say the VP44 once you start throwing in bigger injectors, cam plates, GSKs, DVs, etc. But p-pump trucks sure run nice when they're tuned up right though.



My suspicion is I have some internal problem on my rig such as a head crack or gasket problem, or maybe a broken ring. I did do a compression test but it didn't reveal anything other than I have 500-520psi on each cylinder so the ol' motor appears to be sound.



Vaughn

 

[Grizzly]

Is you 05 a 12v

oops!

 

[DieselMinded]

Does this count ??



http://www.dodgedieseldatabase.com/12vv.zip



DM