Engine/Transmission (1998.5 - 2002) Idle miss plus

[Ncostello]

I've only had my 24V two days now and have noticed a couple of things that seem "amiss"... no pun intended.



1. When idleing, I put the hood up and lean against the front fender to watch and hear the engine. While doing this I noticed that every 5-10 seconds, sometimes a little longer, the engine acts as if it "misses" for just a split second. I can feel the truck shutter instantaneously, although it is just barely noticable. But I can notice it. If it were a gas engine, I would say that it lost spark for a split second and wasn't firing. But now I guess I would have to say it isn't getting fuel for a split second. Sound like lift pump trouble symptoms or VP 44 symptoms?



2. Upon coming to a stop sign and depressing the clutch, the RPM's drop to almost idle but not quite. It seems to hang maybe 50 or 100 rpm above idle for about 2 seconds then it comes down. Is this normal??



3. Finally, when I turn the cruise on and set it on say 55, it very slowly keeps increasing speed until I switch it back off at say 65 mph. What gives.



I was just wondering if this could somehow be all tied together.



I haven't done my fluid changes yet, or tested lift pump pressures yet, or changed all the filters.



Its a 99 2WD QC short bed ST with a 5 speed, and bone stock.



Thanks for any help to a new 24V owner who dont want to drive it until I make sure I'm not in the danger zone.

 

[Bigramguy]

The cruise overshoot may be covered in this TSB. I believe it was extended for the newer model years.



http://dodgeram.info/tsb/1995/08-16-95A.htm



Check it out.



I would do all the required service first,and maybe throw a fuel pressure gauge on it to check the lift pump pressures first.



As far as the idle staying up for a few secs,I have noticed this on several 24V I have driven,and I'm sure it is normal. My 12V doesn't do it,but it has no electronic controls either.

 

[Ncostello]

Thanks,



That cruise control fix sounds like it may fix my problem. I didn't let it run its whole cycle like TSB described but I will do the "unlearn" method to try and correct. Thanks a million. I suppose I better install a fuel pressure guage immediately when I change the fuel filter.



Gotta get this stuff solved. Thanks again.

 

[Bigramguy]

Neil



There is another TSB for the cruise as well if the above doesn't help.



http://dodgeram.info/tsb/1999/18-08-99.htm

 

[MWilleford]

Neil, congrads on the new truck!

1)My truck had a very similar miss (Exactly how you describe it) and was only doing it when warm. I could feel the miss through gear shifter when was resting at a stop light. I had the miss for about 3-4 months (12 fuel tanks). After reading a few posts about fuel tank alge, I added some Biocide cleaner to the fuel tank. This fixed the problem and it has not returned. I first thought it was my lift pump, or injection pump.

I found Diesel-kleen's "Biocide" at Tractor Supply. It was a little spendy, but the bottle should last a long time. (P. S. I added full bottles of the regualr DieselKleen's fuel additive and it did not clear up the problem. Buy the Biocide.

2) the 99 engines with standard transmissions do hold the engine RPM up until the vehicle speed is below 10mph or so. Mine does this. I guess it does this to keep powersteering and brake functions up to power? This little "high idle" had me worring, as I noticed it right after I bought my truck (used)



Best of luck, I almost pulled my hair out trying to figure out the idle miss. For me, it started right after i filled the truck one day, and stopped right after i used the cleaner. Just my . 02 cents!

 

[MWilleford]

Try this link:



Link-- fuel tank- alge

 

[Ncostello]

MWillieford:



Interesting... . very interesting. I've heard of this but have never seen it. Now I am wondering, I could take out my fuel tank and clean this membrane on mine. But, how do you clean out the inside of the fuel tank? Pour 5 gallons of PineSol in it and swish it around. I would hate to go through all that trouble and not be able to really clean out the tank real good. At least then, I would know that I am starting out with a clean "baseline". Seems like cleaning out the tank could possible eliminate ALOT of headaches... which makes me wonder more... . I just wonder if algae could be the cause of alot of lift pump failures... or what appears to be a lift pump failure since it could block the flow significantly... HMMMM. Thanks for that info.



PS. I realize it aint exactly a 5 min job, but is removing the tank fairly straightforward? Any tricks or "do not do this or you will destroy your XXXX" things come to mind.

 

[MWilleford]

Neil,



I never fully removed the fuel tank. I started to remove the tank, but realized it would take longer than i planned and had other things to do (flush the radiator & oil change). I know you have to remove the fuel lines before dropping the tank.

I added the biocide and never removed the tank, or checked for a vacuum on the suction line of the liftpump. I was going to flush the tank with kerosene, and soak the membrane in Pinesol. I wish that I had seen the membrane prior to adding the biocide.



I have added a fuel pressure gauge, and am working on a fitting to hook up a vacuum gauge at the inlet of the lift pump. But now I cannot prove anything since my symptoms went away. I too was wondering if lift pump life was affected by this (hence the want to install a vacuum gauge). I have never seen anybody address the lift pump failure as cavitation, or not? That would kill it though. HOWEVER, after I fixed the miss problem in May, I had to replace my lift pump in June Again, i cannot prove that the lift pump failed due to the membrane



I have started using Power Services- Diesel Kleen additive at every tank. So far so good Oo.



Let me know what you find if you drop the tank! I think there is a kit available from Cummins to check the vacuum at the liftpump inlet. I stopped worrying about mine since I now have a fuelpressure gauge, no miss, and a new liftpump. -Matt