dewclaw

I have this nagging problem after warm-up . It sounds like one cylinder gets a miss in it . It idles perfectly when its cold though. After warm up , it has a nasty rough idle.

After warm up, If throttle up to 1000 RPMs it runs perfectly smooth. When I let it back down , it rocks the truck with a bad idle.

The injectors are fairly new. I bought a set of RV injectors from an outfit in Florida, Pensacola I think.

Is there anything electronic that could be causing this problem !??

Should I do a pop test on the injectors at this point ?

What would some of you pro's look at !?

The valve clearances are all perfect.
This truck does have 337K mi on it but, I change the oil every 5k and I don't abuse the truck.

Low compression on one cylinder ? !

I need some ideas, I'm perplexed !!

Thanks in advance .

Dew

dewclaw

any thoughts fellers feller-ettes ?

RowJ

Try disconnecting the Edge box. They have been known to ocasionally cause similar problems.
Also, Ever replaced the VP-44. possibly with a HPVP-44? Just fishing.

Has rough idle been there since installing RV-275's?

Just noticed... "Rough after warm up". You saying smooth till it's warm?

RJ

Chass

Dewclaw,

I have, what sounds like, the same problem. My truck had a miss/rough idle when I bought it with 207k on it. I put an Edge Juice with attitude in it, same problem, new 100 hp jammar nozzles, same problem. I even put a FASS pump in when I did the nozzles.

It only does it when its hot/warm. I also noticed when the AC kicks on, it idles perfectly. When the ac kicks off, the miss comes back. But when its idling after coming off the freeway at a light, thats when it does it the worst and the idle is 100 to 150 rpms higher than it should be. It doesn't seem to get any worse after 30k miles or more.

I know my truck had an updated injector pump put in it by Dodge at 90k. It was supposed to be the one that fixed all the VP44 problems. But that pump now has 150k on it or so.

I've asked around about the problem a lot. Everyone seems to think its the fuel pump . . . but I'm hesitant to throw an expensive fuel pump at a good running truck that only has a mild miss at idle. Otherwise it runs PERFECTLY.

Chass
ct

dewclaw

ROWJ


Try disconnecting the Edge box. They have been known to ocasionally cause similar problems.

***Yep , I tried disconnecting this. No cure

Also, Ever replaced the VP-44. possibly with a HPVP-44? Just fishing.

*** I made a bunch of overtime money and bought another VP44 , no help . Now I have two good VP44's

Has rough idle been there since installing RV-275's?

** it was slightly rough, same miss with the stock injectors. Its a bit worse now.

Just noticed... "Rough after warm up". You saying smooth till it's warm?

** yep it runs perfect until its up to operating temperatures.

I can tell that you think exactly like I do , I tried all that stuff.
Now Im hoping that you are a little bit smarter than me. Thanks for the interest in my problem here. I hate it when Im at a stop light and the bed of my truck is rocking from the miss. Its super annoying .

Let me know if you have any other ideas ! Please !
Thanks
Dew.

dewclaw

Chass , l lets stay tuned , maybe we can both find our problem !!!! I really want to get this fixed !

Thanks for the reply !

Dew.

dewclaw

Hey Chass, yep , when I turn on my A/C the idle is almost perfect .

I know that the A/C puts a demand on the motor so the the idle control gives it a little more fuel .

I am wondering , is there a "mode" during warm up where the computer (or?)
does somethinhg to the timing / fuel mix / or something like that ? Maybe this mode is not turning off after its warmed up ?

I know that gas engines have this sort of thing . There is a fuel enrichment while its warming up then it goes to "closed loop" and shuts off the enrichment when at operating temp.

Does the 24 valve have any sort of thing that happens only during warm-up ?
I know it has the intake air heater during warm=up but I doubt this is he problem .

I know there are some gurus on this page so hopefully they can help us.

Dew

RowJ

Just fishing again but..... rough only after warms up does not point to fuel pump, intake air heater, or computer adjustments after cold idle!
My guess is some kind of leak, either internal or external, after components warm up and expand.
What are your idle rpm's when warm?
How's fuel mileage?

Never read or heard of this scenario... now two of you??

RJ

Chass

After the upgrades I had a fuel leak so I tightened all my injector lines with a home made wrench. They were all loose at the pump. They are tight now!

The RPMs are normal when city driving and coming to a stop. The RPMs always run high when I come off the freeway towing a heavy load. It settles down after a little city driving.

I think it has gotten a little tiny bit worse of 40k miles but its hard to be objective about that since I'm so used to it.

As a side note, I had a buddy who put a hotrod VP44 pump in a non HO truck and he had a terrible miss just like mine but exagerated. He put a stock pump back on and it runs fine.

I still think it could be the pump. It seems to me like a worn out pump could create a low pressure situation on a cylinder or two but I'm no pump expert.

I've just decided to wait it out until it either gets way worse of something quits working . . . 40k later and still working great.

Now if I could just figure out my tranny, pulled it out again last night

dewclaw

Well the truck idles as it always has , at 900 RPMs.

Mileage ? well.... hee hee ... I havnt checked for quite a while. I used to be so good about that.

So are you thinking air leak ? Fuel leak ? I mean air in the fuel ? I did run a clear hose fron a port on the downstream side of the fuel filter, into a bucket . No air bubbles at all, it ran clean.

What kind of leak are you thinking Row ?

I hope that its not some sort of compression leak in one cylinder!! $$$

I was wondering if it was something electronic deteriorating , and when it warms up ...........?

Bad injector ?

Im at a loss !!
Thanks for your interest Row. I sure hope we can drum up enough discussion to figger this thing out . I really like this truck . She has done a lot of work for me and Im kind of getting attached to her ; )

Dew

dewclaw

Does anyone think that my problem could lie in the APPS ? ( dodges acronym for the throttle position sensor right ? )

Dew

gyanko

I just installed a new rebuild 44 pump, starts and idles great when cold and warm it sounds like it's got a miss. noticed when the air conditioning is on it idles fine.
What did you guys do to yours to fix this problem?

Evansdon72

Did you ever figure what the problem was? Mine is doing the exact same thing

SIXSLUG

Try resetting the APPS.

Evansdon72

Already tried that, when it has the miss there is no fuel going to the #1 injector. I have cracked the line in Neutral or Park and don't get any fuel, drop into gear and fuel comes out. Changed out ECM still same problem, could it be the VP44 there are no codes or history of codes.