have a 2001 dodge ram 1500 5.9 4x4, yesterday the truck started to idle very rough and the check engine light came on, i scanned it today it was cylinder 5 missfire, changed the plugs and checked the wires have spark in all, it was still running very rough so i changed the #5 injector the same problem, when at park very shaky, when i put in park and let off the brake to let it roll it kind of stuters and starts to roll, but when i drive it is very smooth or when at park and i hit the gas the shake goes away, any ideas what else can i do to get the shake away and have it running smooth????

 

Are the plug wires routed properly? A crossed set of wires could cause one to misfire. The wire will still test just fine (spark), but it won't fire properly.

 

I went through this same routine with mine several months back. Turned out to be a cracked head. You can perfom a leakdown test on your #5 to either rule out/confirm a cracked head. Best of luck.

 

ye all the wires are pluged in right, can it be because i use 87 gas???

 

clean the IAC port on the Magnum 5.9V8 engine to eliminate that possibility,
as they are prone to get 'sticky' with carbon deposits
and if your missfire goes away with a little throttle that is a clue for IAC as a root cause

i usually use the official $7 spray can of Chrysler Combustion Chamber Cleaner
and put about one third of it down through the IAC port behind the two big throttle bores, then put the other thirds of the spraycan through the vacuum nipples on either side of the intake manifold

it is a good idea to check your ignition wire layout
against TSB 18_48_98

http://dodgeram.info/tsb/1998/18-48-98/18-48-98-v8.htm

 

Hank,
I am having an occasional rough idle also. I did the plug wire reroute and no change. I don't understand the IAC having any affect on rough idle. Could you explain more?
Thanks for the great info you provide.

 

the IAC (idle air control) motor is supposed to adjust the idle smoothly by leaking some air past this little port. it can get dirty and the tiny little actuator can hang up. it is also easy for the IAC to get damaged.

to control the rpm
the PCM computer reads the pulses from the CPS sensor
that is hidden down behind the engine where it reads notches on the flywheel as they go past,
then the PCM controls the IAC to let in air
and adjust fuel injector on time to match the air from the IAC
and this whole chain of events
holds the rpm steady and smooth

if the IAC sticks,
or the CPS misses pulses from the notches,
or the wiring to the PCM computer has problems,
or some of the fuel injectors have deposits causing them to stick
all of those things can cause a rough idle
that may smooth out as the throttle is applied.

of course,
ignition parts, spark plugs and fuel injector problems
can also cause rough engine running,
but most of those usually get worse (not better)
as more throttle is applied manually

the Magnum 5.9V8 is not particularly a smooth idler anyway,
perhaps due to the factory spec camshaft overlap & centerline retard
judging by how adding Rhoads style lifters affect the idle:
http://tinyurl.com/55uoev

 

today when i was idling i heard some slight knock from the bottom of the motor as it was idling very rough, as i apply gas the know and roughnes goes away, i changed the IAC, cut my cat out, and put the 91 gas in, got a little better but i still feel a little shake, what sensors or what should i try next??

 

HankL,
wow, thanks for the great info!
I did some internet research about diagnosing misfires/ rough idle and it can get complicated and frustrating. It's actually nice when something clearly fails or blows up! It's tough to diagnose an intermittent problem. I have wished for a constant rough idle thinking that might be easier to fix. However, I'm not wishing for that anymore cause it is nice to have a smooth idle occasionally. Ha Ha.

 

Hello Iam new to this site hope you can help I have a 2001 dodge Ram Sport 4x4 5.9 70.000 miles have had very little trouble over the years.its a weekend driver problem iam haveing is when i put heat setting on air or heat say vent as iam driving it will switch to dash sit it on floor it switch to vent etc. Went to dealer they sold me a small in line canister . They said that shou;d do it it did not help put a new in line vacum thingy in vacum line by intake no luck checked all vacum lines far as i tell all looked good. Hope some one can help. By the looks like a great site for Dodges Thanks for all your help.