Ok I know this has been covered a few times, but none of which apply to my situation. Upon cold start truck runs rough at idle, after warm up it smooths out but I can feel a slight miss once in a while stopped at a light idling. Change spark plugs from bosh to autolight which none of were fouled, new wires and are routed correctly, new cap, and rotor.

Replaced fuel pump, the roll over valve was gone. Sea foamed twice and there was tons of smoke. Getting codes random miss fire, cyl 5 and 8 miss fire, but light will turn its self off and then come back on within the next couple cold starts. Need to smog within a month, not sure if it will pass if I can get in there with the light off. Any suggestions are greatly appreciated.
98 ram 1500, 134000 miles on 5.9l, also the truck sat since 05 and got on road 3 weeks ago. Thanks

 

Have you checked your plenum yet?

 

Yes I have, there is a slight residue at the bottom of intake that I can see. After reading other posts I thought that for sure a plug would be showing signs of the plenum leaking. The plugs I pulled out all looked good.

 

What spark plugs are you using?

 

have you checked your cap and rotor, and plug wires as well?

 

Autolite 5224, the truck had bosh platinum's before. After new plugs there was no change in Idle

@ Dodgeboy, the cap, rotor, and wires were all replaced at once. Also re-routed wires with the wire loom with no change in Idle.

 

How bad is it? It sounds like you have been thru most of the stuff that would be likely culprits. Given it is only when the engine is cold..... I doubt it would be O2 sensors. Fuel pump is new, so it hadn't better be fuel pressure...... How long does last till the idle smooths out? More than two or three minutes?

 

Fuel pressure is 45, it will smooth out after it gets to operating temp. Just now I left the house and the check engine light turned off and it is running perfect. I think I'm going to smog it while the light is off. The only thing I havnt checked is compression. There is no smoke and no oil consumption. Average 14 miles to gallon. I am stumped.

The miss isn't bad at all, its just enough that I can feel it in the floor board and enough to make me worry about emission test. But besides that it has lots of power. Forgot to mention that when I disconnect the fuel injector there is no change in idle speed. I swapped the injector around with no change still 5 and 8 miss fire. I sure hope it isn't cracked heads.

 

Given that the problem is intermittent.... I don't think its a mechanical issue. Possible cam or crank sensor on its way out, but, those are really hard to tell which one is bad.... unless one of 'em actually sets a code.

Might want to check your plug wire routing again though..... and even though they are new.... wait until it is dark, and then hit 'em with a light mist of water. See if you get a light show.

 

Wanted to update, I felt the miss in overdrive about 2000 rpms, but when accelerating or de-accelerating I couldn't feel it. Didnt get a chance to mist water on plug wires last night, I had to do a timing belt on friends honda and what a pain that was. So today I decided to pull the new cap and rotor off to check the camshaft position sensor to clean.

There was small deposits on the pickup of the cps, but nothing to bad. What I saw on the cap though looks strange to me. Looks like the coil is firing early or late, but not sure if this is normal. Please let me know what you think.