Engine/Transmission (1998.5 - 2002) 98 1/2 Misfire at idle only when at operating temp.

[EthanWhite]

Like the title says, If I get off the freeway or pull up to a light I can feel a moderate misfire. It is completely random, When I start the truck cold it does not misfire. It only seems to be when I have just been driving the truck. If you let it idle for awhile, it will stop then come and go. Like I said it seems random. I have read somewhere that it could be the injectors or nozzles. Does this sound Right? The truck is a 98 1/2 Dodge 2500 with 158,000 Miles. This problem has developed in the last 10,000 miles. The truck does have an Edge chip. I also use Delvac1 Synthetic. I'm getting sick of feelin it do this an would like to figure it out... Also, no check engine light has ever come on.

Any help would be appreciated!

Thanks!

Ian White
CVM Machine
Chehalis, WA
360 520 3013

 

[EthanWhite]

I tried seeing if it was the edge box, and still the same with it disabled it still has a lillte misfire or bump. ANYONE?

 

[FourBarR]

I have a 98. 5 with 500680kms. original vp-44mand original injectors. neve had any mis fires rough running or starting problems. I have always used mmo and howes meaner in every tank of fuel. First thing I would do is get codes read . good luck with it . let us know if you have codes set.

 

[EthanWhite]

FourBarr, there are no codes present.

 

[CKelley1]

it is the vp44 had several do it

 

[EthanWhite]

VP 44 was replaced at 134,500.

 

[MWmB]

I have a 1998. 5 that was doing the same thing (285,000 miles) after a long run on a hot day. The injection pump is cooled with the fuel circulation. Fuel pressures were OK but toward the lower range. I installed a FASS 150-95. Never did it again. Also, truck runs much better and quieter.

 

[EthanWhite]

could it be a faulty injector pump?

 

[RHoch]

i have the same thing. its a random mis and only at operation temp. i have a fass 150 pump and edge comp box and i still dont know what the problem is. If you find out let me know. mine just set off a code for no com from ecm to injection pump. I dont know if this is part of the problem or not. ill let you know if i find out something.

 

[Kelly lyssy]

i have 1998. 5 that had missfire when hot ,It was a bad injector

 

[CKelley1]

it is the vp44 also had several of them do it

 

[EthanWhite]

I talked to Cummins Northwest today (because the dodge dealer diesel 'mechanic' is a fool), and they seem to think that it is a injector problem. Dodge Mechanic says it isn't a APPS, but I am unsure. The miss seems to go away for awhile when I reset the apps, or if I shut the truck off while its missing and start it back up it won't miss for a while but it will start again. The truck has a tst box on it now. Why would a bad injector cause an intermittant miss only at operating temp ( it only misses when engine coolant is above 165 degrees farenheit).



Any Ideas?

 

[EthanWhite]

Also the miss is intermittent, it comes and goes and sometimes it won't miss, but other times it sounds horrible, this has gotten progressively worse over time.

 

[hcole]

For what its worth Ian, my 2002 is doing the same thing yours is. I just replaced my APPS because of surging and the surging stopped. The miss is only at idle and it comes and goes when it is warmed up. Its noticeable but I'm not worried about it. I think it may be just a minor problem with an injector.

 

[BEmmert]

My 98. 5 did this as well, turned out to be an injector. Once replaced it stopped and has not done it again.

 

[EthanWhite]

Alright what injectors should I go with?

 

[BILLVO]

It is probably the computer on top of the VP44. It has been an issue since the inception of the vp. I think bluechip even has an article about it on their website. I have an II HRVP44 that does the same thing. Only does it when engine is hot, never does it in the winter. I have been thinking of seeing if II wil correct it since they are supposed to have the better electronics installed on the HPVP44anyhow.





Below is off Bluechips VP44 troubleshooting page here



ROUGH IDLE/MISS AT LIGHT THROTTLE



This is almost always the computer on the top of the injection pump, as long as there is appropriate lift pump pressure, no air in the fuel lines and no codes pertaining to Crankshaft or Camshaft sensors. By now you know what a bad computer means; REPLACE THE VP44!

 

[CKibler]

I had the same problem. Change apps, check and adjust valve lash,also changeded injectors. All done with no help. I went with a Blue chip rebuild. Easy to put in and runs better than new.

 

[JLandry]

Alright what injectors should I go with?

Hi Ian,



I'm a bit skeptical you have a VP44 problem. Seems to me if it you did, you'd be having more problems more consistently. But of course anything is possible. Heck, it could even be something as simple at a faulty intake air temp sensor or MAP sensor!



I'm not sure if you've mentioned this or not, but have you verified (measured) that you have adequate fuel pressure at the VP44 inlet at all times? The absolute minimum you should see is 5 psi under wide open throttle. Low fuel pressure can cause strange things and is a big strain on the VP44.



But regarding the injectors...



A Chrysler DRBIII scan tool, or the Cummins Insite software (with appropriate adapters) can selectively kill one injector at a time to help isolate if you have one or more bad injectors. If the engine miss doesn't change when a troublesome injector is turned off, then you've likely located a bad injector. Any Chrysler dealer will have the DRBIII scan tool and Cummins NW should be able to use their Insite software on your engine *if* they have the appropriate adapters for the Dodge truck (not all do) and know how to use them.



Another option for you to consider... I live up in Shoreline just north of Seattle and have a DRBIII. If you get frustrated enough and want to drive up some weekend, I'll be happy to help you troubleshoot this. We can kill the injectors and check for other possible problems. I also have a fuel injector tester (pop tester) which is used to test the spray pattern and the exact fuel pressure when an injector opens. Just send me a PM if you ever want to get together.



Anyway, injectors can leak, clog, and/or stick intermittently as they get older and dirtier. As to why it would only happen when the engine is warm, well one theory I could throw out might be this (could be completely wrong): When the fuel is cold it has a higher viscosity and possibly the VP44 fuel injection pump can create more pressure to operate the injectors. When the fuel is warmed up, then possibly the injection pressure is a tad bit lower so a troublesome injector doesn't open so consistently.



With as many miles as you have on the engine, replacing the injectors couldn't hurt anything (except your wallet) at this point. Some folks believe injectors should be replaced at about 100,000 miles anyway, but in practice most of us just wait until there's a problem. If you decide to replace the injectors outright, then either the stock Bosch injectors or the slightly upgraded "RV275" Bosch injectors can be found online for as little as $60-70 each. The RV275 injectors are said to produce slightly more horsepower and fuel economy (with careful driving). I presume they achieve this by having a slightly lower opening pressure, which would effectively advance the fuel injection timing.



To help with your search, the injector part numbers are...

Bosch:

0432193629 = stock injector for manual transmission

0432193630 = stock injector for automatic transmission

0432193635 = "RV275" injector​

Cummins:

3944828 = stock injector for manual transmission

3944829 = stock injector for automatic transmission​

BTW, a set of new Bosch RV275 injectors can be ordered from Amazon.com for $360 with no core required:



Amazon.com: Dodge Cummins 24 Valve 300HP Diesel Injectors: Automotive



Good luck,



John L.

 

[EthanWhite]

Great. Thanks for the offer! I know I have adequate fuel pressure ( I have a fass ddrp, and a cater frame rail mounted pump). I am thinking it is more an injector problem myself, because it has gotten progressively worse which doesn't seem to insinuate a electronics issue (seems to me that if it was an electronic issue it would either miss or not). The only thing that I question with the injectors is: Why if i bring up the rpm's by as little as 50 rpm's does he miss go away? Also you can feel it miss when you rev it up to oh say 1500 rpm and when the rpm's are falling you'll feel it stumble. As for any drive-ability issues, they are non existent. It still seems to run as strong although I have been noticing slightly less fuel economy. Maybe it's all in my head... . haha