5.9L engine idle problem
 

Hello everyone,
So here's my problem, i'm taking my truck to a mechanic in afew days to try and get this fixed but from searches on the internet i've found alot of people with this happening and in every case it seems they've done something different to fix it or couldn't get it fixed and alot of them complained about the end cost after a mechanic went through and replaced part after part.....so here's the problem, i bought my 99 ram 1500 5.9L 4X4 recently and drove it home with no problems (200miles) a day or two later i had it running at idle and all of a sudden my idle drops to about 5 or 600rpm and it sounds really rough like it struggling to stay running.....i reved it up once or twice and it went back to normal idle...around 900rpm i think, so i didn't think much of it.....well later on i was driving and came to a stop and while sitting there idling it suddenly dropped down to the 5-600rpm ranged and was idling rough, engine shaking ect and the light turned green...now i went to take off and the engine was stuttering and cutting out and i started to slow back down to almost a standstill, at the same time i heard popping or backfiring into the air cleaner i believe...i stepped on the peddle to the floor and it cut out for a second then the engine roared to life and i got upto speed (35mph)....now the CEL has come on and i've read the codes and it says its running rich and the O2 sensors are bad, we cleared teh code and i continued driving it....it still does it completely randomly and usually does cause the CEL to come on again.......now i went through and replaced plugs, wires, cap, and rotor....exhaust seems to have good pressure comming out the pipe but it still seems to do this...its completely random....does it when its warmed up or when its cold.....might do it once in 40 miles of driving or several times...there's no pattern........i should also mention it seems like its getting really poor mpg....i havn't done the math to see exactly what my mpg is but i can put half a tank in it and drive it alittle around town and go home and i'm almost back on E again.......... dont know if this is part of the problem but i've noticed that to hit hiway speeds (70mph) i seems like i gotta have the peddle to the floor........anyway, i just want some idea of what it might be so that i can point the mechanic in the right direction without costing me an arm and a leg in parts tryin to fix this......mechanic looked at it once and because it didn't throw a code and when he test drove it afew miles it didn't do it he thought it was fixed........PLZ HELP!....ty.

welcome to df.
post your truck year, engine, etc in your signature so its easier for us half blind old people to find it.

post your actual CEL codes, don't translate them.
have you replaced your front O2 sensor yet ?

I have almost the exact problem on my 2000 ram 5.9 ext. cab w/ 104,000 miles on it and I have changed cap, rotor, plugs, wires, iac and tps sensor, coil, theromstat(not related to problem), one of the two o2 sensors(sensor 2) and none of these have fixed it. My next approach is checking the fuel pressure, changing the temp sensor or injectors but other than that not sure but will keep tryin. hope this helps and or if ur mechanic fixs the problem please post solution, thanks and good luck.

1999 Dodge Ram 1500 Laramie 4X4 ext cab 5.9L

still tryin to figure out how to put it in my signature.
also....dont know if this has anything to do with it but i do hear a very very slight and quiet sucking sound when it idles rough...and i noticed for the 1st time yesterday that it will randomly rev upto about 2grand rpm when idling....did it once in about 15 minutes....aside from that occasionally i'll barely touch the peddle and it will go upto about 2000rpm and seems like it sticks there for a second before it comes back down....now it doesn't always do this and i'm just mentioning it incase its connected to the problem.

Check your TPS.

Change the pre cat O2 sensor.

+1 for oxygen sensor 1 (pre-cat). The second sensor does nothing for the running of the engine, just tells you when the catalytic converter needs replaced. The first sensor helps the PCM determine the air/fuel ratio, so its very important. This would explain the lack of power/sputtering AND poor MPGs. What was the exact code?

Just to recap:

You said you had codes saying that the engine was running rich, and that ~both~ O2 sensors were unhappy. It sure would be nice if problems could be fixed by clearing the codes. It would be helpful if the posted any codes you're getting now, especially the O2 sensor codes. If the engine really has been running rich, it's possible that the cat is now screwed up. You might just save yourself a lot of trouble in the long run by taking it off and having a look-see inside it, especially if you're getting a code that says it's bad. Got a lift, a torch, and a half hour to spare?

Another thing: The randomness and popping back/misfiring clues just made me think of the crankshaft position sensor (CKPS), not to be confused with the camshaft position sensor (CPS) in the distributor. I have read accounts on here of how a bad one can cause misfiring, and I'm guessing a ~really~ bad one can be very hard on your starter. I've been having a random stallling/stumbling/misfiring problem with my 94 318 and my next attempt is going to be the CKPS.

The random high idle w/slow return sounds like a separate problem: as sticking IAC. The low/sucking idle, though, sounds like the pre-cat oxygen sensor.

I hope you get it fixed without any misadventures along the way.

thx guys....going to my mechanic today with these suggestions....dont know if it matter but my CEL went off this morning and hasn't been back on...should still show a code when we check it tho.