’99 1500, 5.2, auto. Bought with 75k now has 200k miles. Tow 4 days a week. Light single axle 12’ enclosed trailer. Truck started throwing a code. Running rough at idle occasionally. Not always and not consistent. Went to Advanced borrowed code reader. Codes were p0300, p0304, p0306. Been a while since I tuned up so a friend of mine being out of work put points and plugs in. Didn’t do wires as I had a set of lifetime wires on the truck. Seem to run better for a day or two and then rough and codes back. Same codes. Decided to try plug wires. Before I could put them on my fuel pump quit. Changed pump. Cleared codes. Dumped a bottle of Lucas fuel injector in and truck seemed to run better with a little more power. No codes for two days and truck seemed to be running good. Pushed it hard yesterday going up hill, late for an appointment, hot weather. Code came back and started idleing rough again. Read code, only p0304 this time. Read a ton of posts and cleaning the throttle body kept coming up. Pulled air cleaner and throttle body looked really dirty. Going to try cleaning that next. Am I on the right track? Any other suggestions or maintenance items I should do for this problem. Suggestions appreciated. Thanks.

 

So you still haven't installed the ignition cables? What about the cap and rotor?

Ignition is the most common source of misfires, but not the only one. I've certainly seen bad injectors on the magnums, as well as broken valve springs.

 

No haven't put wires on yet. Cap and rotor where replaced. Would injectors or broken springs be an intermitent problem?

 

OK. Not a lot of time today but I would like to figure this out. Code was p0304 cylinder 4 misfire. I just replaced the #4 plug wire. Started it up. Still have pcm light on and still idleing rough. Pulled negative cable and turned ignition swith to start for 1 minute and cleared pcm. Started up. Runs smooth idles smooth. Have to go on a 50 mile run this afternoon will see what happens.

 

You can get a misfire from the wires obviously, when you do decide to do the rest make sure you install them so that they are not crossing over each other or touching as best as you can.

 

OK. Replaced plug wires. Cleaned throttle body, what a mess. Replaced IAC, it was way way crudded up and the plunger popped out as I was cleaning it. Ran Lucas injector cleaner, one tank, then ran chevron teckron the next. Truck runs a lot better. Real smooth, good acceleration. Felt like a very slight miss while idleing. Plenty of power. No obvious miss while under power. Thought it was fixed. Drove 75 miles. As I was patting myself on the back I got a code again. Same codes. P0304 and P0306. What next? Help.. How do I check the injectors. What else should I check.

 

Is a injector cleaning as sold by Jiffy Lube worth a try?