Engine/Transmission (1994 - 1998) engine misses, HELP!!!!

[RKraiza]

I have a 96, 12 valve that misses consistantly under load. It is most noticable in the 1200 to 1800 RPM range. In short, Here's whats been done in the past two months by myself and Cummings Northeast, a certified dealer who likes to change out parts apparently(not recomended). New injectors, no change. New lift pump, no change. New high preasure lines and bango fitting, no change. New injector Pump, no change. New injector pump again!, no change. New head,(yes, you read this right) no change. According to cumminngs, everything checks out to specks and it shouldn't be missing. It seems almost like an air problem but I can't figure this out for the life of me. Here's the stats, on startup, misses and runs rough. Once running cold, runs extremely good with a slight miss. Once warmed up runs good in the hih RPM range but misses in the mid range. The EGT's appear to be very high when it is missing, with the boost being in the normal range. I can not duplicate the miss unless operating vehicle under load, so a thermo gun is not an option to figure out which cylinder has the problems. Any help is appreciated.

 

[Joe G.]

The only thing I don't see in your list of stuff is the fuel heater/pre-filter. If that was not changed you may have an air leak in the electrical connector. Try taking the fuel heater (looks like a hockey puck) out and see if that fixes it. To do this you remove the pre-filter from the bottom with a 17mm socket. Then use an allen wrengh (8mm I think) to remove the fuel heater. Put the pre-filter back on without the heater. There will be air in the system so it will run rough for a little while. Then give it a try and see if the missing goes away.

 

[Jeff H]

Gall you think they could have tested the parts before they replaced every thing. Sounds like they took advantage of you??

Some thing is going on between the fuel tank to the lift pump.

To bad you couldn't run it on a dyno and put a load on it.

 

[Vaughn MacKenzie]

Gall, make sure the timing is correct, maybe set it to 15. 25 to 15. 5 degrees. Buy a prefilter service kit, and the 90 deg. hose between the prefilter and lift pump and see if that helps.



With the injection pump swapouts I assume the overflow valve was replaced.



Joe G I never heard of the electrical connector being a possible source for air. I've been having a stumble/miss on my '96 for awhile which I've tried tracking down to no avail. I have been told it could be a combination of having a . 010" over headgasket and a high-mile motor. But I will have to try your trick! Thanks!



Vaughn

 

[dalton4]

If a load type dyno was available, I would get me a infrared temp reading gun and put the truck on the dyno. With it loaded and running in the cylinder missing rpm range... you may be able to detect which cylinder is the problem if related to just one and then direct your attention to it.

 

[Joe G.]

Vaughn,



The heater element burns up right at the back of the connector. This causes one of the connector pins to get loose. The result is a small air leak when it's running and, maybe, a little fuel drip when it's not. I have three pictures in my Readers Rigs album to show and explain the problem. For some reason with I tried to post them here I got an image server is down message.

 

[RKraiza]

Thanks to all for the input. I will try the heater element removel and go from there. Any more ideas are appreciated.

 

[RKraiza]

I changed out the fuel heater with no improvement noticed. This thing is really starting to bug me!

 

[DKarvwnaris]

Sounds like Cummins Northeast needs to have their parts they installed tossed through their front window. Did they at least give you a hand shake for bending you over so far? As many miles as I have put on the four dodges I have had, not counting numberous repowers to other makes with 5. 9's, I have only had the miss issue happen twice, it was a crack in the fuel line leading to the #4 injector on one truck and a preheater wire burnb out as mentioned on another. Missed it after six look overs and numberous steam washes to locate it. Hope you get it fixed without further funding the Cummins Northeast "Cranial pelvic relief" fund.

 

[RKraiza]

You guy's are definatly right about Cummins Northeast. If I didn't need the truck so much, I'd drive it through there front window! Just to give all with a similiar problem an update, This is turning out to be a possable torque converter issue that is duplicateing an engine miss. I have recieved post from othere members with similar symptoms and this is the road I'm going down now.

 

[DKarvwnaris]

Ahh, an automatic, sorry didn't see that equippage in prior posts. I know where find nv 4500's and 5600's direct from NV (New of course) for very reasonable costs. If the torque converter is starting to act up in your rig, I would very carefully check the fluid in the pan for any metal traces, I have yet to see a torque converter start to go without leaving parts of itself to wipe out the valvebody and related neighboring parts. Unless you have a bum leg or city driving more than 70%, dump the slushbox, its an easier remedy than you think on a dodge platform.

 

[RKraiza]

Bad news, It's not the trans. I put a "mysteryswitch" in today with an indicator light to show the TC lockup. After manually locking the TC, the truck still misses in the 12oo - to 1600 RPM range while under load. I also replaces the TPS with no posative change. I"m about ready to become a FORD guy at this point! any more suggestion are welcome.

 

[nfox]

Engine Miss

I would have to say get your timing rechecked to make sure it is at 15* or 16*. When the truck is cold start it and let oil pressure come up and speed the motor up to 1500 to 1600 rpm and see if it misses, if it does your timing is off. Just my thoughts.

 

[Joe G.]

Watch your tach when it misses. If it bounces up then it's not a miss. That's what mine was doing when I thought I had a miss. When I saw that I knew it could not be a miss. It turned out to be the TPS in that case.

 

[JoshPeters]

If the EGT's are going to the high side when it misses your getting fuel. It sounds like an air issue to me. Is the Valve lash set correctly? Could the intake valve never be fully closed? Judging by the work that has already been preformed they should have taken care of that when they did the head. I'd maybe look at the fuel supply/return lines. They get dry and cracked and usually result in a nose up hill starting problem, but given time... they could get bad enough to give you other problems as well.



Where are you from? Maybe there is a Member here who would be able to try and assist with your problem.



Please don't go to the dark side!

Josh

 

[RKraiza]

started it this morning, let the oil preasure come up, then immediatly brought it up to 1800 rpm. It missed all the way up and then leveled out. did this test repeatedly with the same results. Doesn't do it once warmed up. I'll bring it in to get the timeing checked, again. thanks for the info.

 

[Joe G.]

Were the delivery valves replaced when the injection pump was replaced?

 

[RKraiza]

I asume yes but am unsure. The pump was rebuilt by a reputable shop, and retested after rebuild with nothing found. I will check with them tommorow concerning the delivery valves though.

 

[Willys]

Did you get this worked out? what was the culprit?

 

[Heepdriver]

I've got a miss to and would really like to know what happened, i seem to remember something about oil filters coming apart and cloging piston squirters and causing a miss, has always been my worry.