injector?

 

My engine has an occasional rough idle and I think it may be related to the valves. I sometimes hear valve ticking when the engine is cold and then it goes away. However, sometimes it is quiet when cold and the valves tick when hot. I plan to be more aware of the rough idle in relation to the valve noise. The inconsistancy of the valve noise has me believing that sometimes some of the valves may not be sealing correctly. I have listened to the exhaust coming out the tailpipe and most of the time it is steady. However, when the idle is rough I can distinctly hear an occasional "cough".

So, the question is: is that cough a misfire from bad spark, bad injector squirt or bad combustion due to a leaking valve?

 

I have a 1997 with a 5.9l, and it idled rough when cold, but ran good when hot. It turned out to be the temprature sensor. There are two temp sensors, one goes to the dash, the other to the PCM. I changed the one to the PCM and have not had any problems since.

I don't know if this is your case, but hope it helps.

 

my motor never idles rough.cold or hot. just so you know.

 

my bet is worn valve seats... just went through all of this. started with rough idle when cold about a year ago.