Engine/Transmission (1998.5 - 2002) 98.5 24v VERY ROUGH Idle (not same old thing?)

[pdxkevinc]

Folks,



I have been pouring through the FAQs and search results and am a bit stumped for info. Not to mention I can't get satisfaction from my dealer service. I'm in dire straights and would really appreciate a clue.



The problem is a very rough "idle" on my 98. 5 24v.



Quick history. at 52k, my truck started throwing a good deal of oil and grey smoke out the blowby hose. Man did that smell funky. Anyway, they pulled the engine, tore it apart resleaved the pistons and did a ton of checks. Supposedly there was no problem found.



Within 3,000 miles of having this service done, it started blowing again, but only when I really put the screws to it (towing the 5th wheel that is)



The worse thing I'm living with now is that when the truck gets hot and I come off of some high RPM driving, the

truck wont come to a smooth idle. It bounces around like an old gas engine that is missing!



I took it to the dealer and they replaced what they called an APP sensor. No fix.



I took it there again yesterday and the goofs did not follow my directions on how to reproduce the symptoms... they said it has a nice smooth idle. They didn't get it hot enough I'm sure. Of course just driving it home from the dealer left me in my driveway with what I'm now calling "bouncing betty"... this sucks.



Here is the real interesting point. After a fresh oil change, the symptoms are much much less severe!



Ideas most appreciated.

 

[jwilliams3]

I would start with an ECM reflash from your dealer.

Next, I would have the Crankshaft position sensor changed (you can do this yourself).

Then change the Cam position sensor.



Also, while your at it if you have not had a new lift pump on your truck, then I would replace it also.



What kind of maintenance has been done on this engine? and are you the first owner?



--Justin

 

[pdxkevinc]

I am the first owner and have followed the scheduled maintence to the letter... except for more frequent oil changes than recommended. I had a 95

12v before this one as well...



Shouldn't a dealer be able to pick up on the need for these recommendations by hooking up diags?

 

[jwilliams3]

I wouldnt let most dealers touch my truck (many reasons).



I stated earlier to change sensors, but rethinking those statements I would do a fuel pressure check, if you cant get the equipment to do the check then I would just change the lift pump ($150 from Cummins).



A dealer with a good tech should be able to diagnose your problems, but there are many variables with the ISB and not all problems are picked up with diagnostic equipment.



--Justin

 

[work2muchplay2little]

I'd be inclined to take it to the mother ship (Cummins) and have them diagnose it. Might cost you less than swapping parts until you got lucky.

 

[pdxkevinc]

Still a shakin and a jumpin

Folks,



I have taken it to Cummins NW. They didn't manage to witness the rough idle. And by the way, it isn't really a rough idle... more like it isn't firing occasionally - really thumps when it is exhibiting the problem



Alsthough it wasn't throwing a fit while Cummins had it, they did replace the Lift pump.



Since then I have really been pushing the issue with the dodge dealer and Chrysler Corp. I'm only in warranty until May.



So I went to the dodge dealer while it was in a particularly back case of exhibiting the rough idle. They really got the point that time! However, they hooked up and ran a huge number of tests to inclde fuel system pressure checks and on and on.....



They suggested I try a different fuel source (yeah, that's really the problem since this has been going on for 12,000 miles).



They say there is nothing to fix. So I'm stuck. I asked them what they will do if I decide to trade it in and their own damn used dealer mgr wont give me a trade value because of this issue... that really shut up the service manager, but I'm still stuck with the rough idle



any ideas will be greatly appreciated!

 

[Ncostello]

I dont think he will have the cam position sensor. A 98. 5 should most likely have the crankshaft position sensor only. Didn't the cam sensor take the place of the crank sensor in 2000? Its about $50 bucks and is easy enough to install.

 

[heliopilot]

What you are describing is a partially clogged injector with a bad spray pattern and low pop-off pressure.



find your nearest fuel injection dealer and bring all six injectors to them, have them perform a pressure test on them(pop-off) this will isolate the bad injector... .



I have seen this same symptom on 5 seperate 24v trucks in New England . .



the dealers with their electronic equipment are clueless to this,

good luck.

 

[KcoleKennyc]

The 98. 5 does have a cam sensor. I replaced both the crank sensor and cam sensor on mine. These sensors are much cheaper from Cummins. I just replaced the injectors with 275's and it idles rougher than before. Also rougher with the clear fuel. Seems to be smoother with the green stuff.

 

[pdxkevinc]

Rough idle fixed

well, it only took me 48,000 miles, a VP44 (at the direction of Cummins), and tons of other failed attempts to smooth out the idle on this bad boy...



Back in Sep, I overheatd. Got the thermostat and cluctch fan replaced and this thing purs like a kitten (as much as a 24v Cummins can).



It has been a long painfull expensive road, but now that I just flipped 100K, this truck is running better than it has in 48,000 miles... lovely

 

[Oil Burner]

So was the VP44 the problem or did the thermostat and fan clutch do the trick?



I too have a rough idle when hot. Not injectors like others have mentioned as I have had this problem through 3 sets.



Jason

 

[GWedekind]

Im going through the same issue... replaced crank and cam sensor, checked IAT, swapped a good map, replaced injectors, replaced APPS, checked fuel for air, replaced fuel with good fresh diesel, good LP pressure and it misses and skips intermittently. Just 2 days ago I got stuck with a no start and it looks like its the VP44 again. I am now on my way to a 4th VP in 152K. The last 3 were all within about 10-15K miles. Heat is the killer of my VP's from what I can tell. Lots of posts about bad VP's on here and I even saw that FEDEX had VP issues related to the electronics on top failing from heat issues.



Hope this info helps you guys... .



Im ready to buy a NEW VP instead of getting another rebuilt but the last 3 VP's were warranteed. New VP's run around $2000 down here in Fla.

 

[pdxkevinc]

folks, it was the thermo+fan_clutch that fixed it... 48,000 mile of rough

idle ... lots of expensive shotgun attempts to fix it... the damn thing was just

running hot...



I'm ****** and happy at the same time... after all, 48,000 miles and I've spared no expense (e. g. , VP44) to get this butthole to idle (not jump around like

a mexican jumping bean)... .



and it took a boil-over and busted thermo, fan clutch to solve it!

 

[Oil Burner]

pdx,





wasn't your water temp gauge running high? Or did you have no idea that it was overheating?



Jason

 

[pdxkevinc]

it was running a bit warm (close to 190), but that didn't seem outrageous to me