Engine/Transmission (1998.5 - 2002) idle problem help please

[Jason Griebel]

on my 99 2500 24 v I am having a rough idle only when it warms up and only at an idle the outside temp. doesn't make a difference I can start it up at 10 deg plugged in or not and it will idle fine until the engine warms up changed fuel filter have super chips programmer does it on all setting including stock installed FASS 150 pump changed ckp sensor installed BD turbo 4" exhaust K&N filter not all done to help problem but nothing helped hooked up to a reader no codes and all sensors looked to be ok need some ideas

 

[RAJohnson]

Idea , MAPP or IAT sensor



Link to where they are: http://dodgeram.org/tech/dsl/mt_2_feb98/fuel_sys_comp.htm



Do a search on them here on the forums.

 

[Jason Griebel]

what is the supply voltage to be to the IAT sensor 5 or 12 volts

 

[RAJohnson]

Just a guess, But I would say 12V

 

[Jason Griebel]

I checked voltages on my map and iat sensor both have 5 volt supply. I also remove to inspect and clean they both looked like new. I have also recently install a boost gauge and pyrometer and I was wanting to know how they should act. what is the highest temp your egt should go to and what should the boost gauges run at.

 

[Oil Burner]

Boost - up to around 20 psi. Probably see around 18 or so max running empty.



EGT - maybe up to 1200*F?????



I didnt' see any fuel mods in your sig so I assume stock injectors and no box, right?



With 4" exhaust and K&N, your egts might peak around 1000 or so, not really sure. Its been a while since I remember stock readings. Plus, my ETH ran hot from day 1.



I've got the same idle problem. I've had it for 30k miles, 4 sets of injectors, 2 fuel systems, blah, blah, blah. I will be watching this to see what you find.





Oops, I just saw that you have the superchips programmer. YOu might see up to 30 psi or so for boost. I never ran one of those, but I bet EGT can get over 1200 or so easy.





Jason

 

[nps]

I had excessive smoke and a rough idle for the past 3 years, with a few 'good' days spread in between. New IAT, injectors, cleaned MAP, even added a pot to my IAT so I could dial-an-OAT but nothing seemed to help.





Another TDR member sent me a new MAP pay-it-forward. Put it on about 3 weeks ago and everything is good, including about a 2 mpg increase.



Truck is just a tad bit slower, but smooth idle and no smoke. I figure the MAP was telling the ECM that the boost was higher than actual. Do I think this is your problem? - who knows until you try it. Swap MAPs with someone else if you don't want to put down the $ until you know for sure it'll help.

 

[Jason Griebel]

I forgot to include that I did put new injector in 50-60 hp gain I saw it hit 30psi empty when really getting in the pedal but most of the time just crusing it's around 5psi How much does a map sensor go for?

 

[nps]

Around $70 for the MAP from Cummins. A bit more from DC - but check both sources.

 

[RAJohnson]

EGT depends on where you installed the sensor, Pre or Post! Pre try to keep it below 1250* for a sustained period, anything over for is OK for a short burst. Post add 200* to what ever you see on gauge.