OK, I have managed to fix everything wrong with this truck, except one thing - an idle misfire and a weird one to boot. Here it goes:

If the truck idles for more than 40-45 seconds, the engine starts to misfire. This will happen in or out of gear - in my garage or at a long traffic light. It will happen regardles of the engine being cold or warm, i.e. I can start it, drive 10 miles, stop at a long light and it will startto misfire or I can start it, let it run for about 40 sec. and it will start to misfire.

Let's say I am at a traffic light when this happens. Now, I have 2 options to fix it - I can either start driving, jump on the gas and rev it pas 4k rpms (usually in second gear), rev the third gear past 3,000 rpms and the misfire will go away; Or I can simply drive it for a few miles and the misfire will disappear on its own.

The CEL never turns on, nor I get any codes (I keep a reader plugged in the truck just so I can check when it starts to misfire). I also don't burn oil or any other fluid.

I have changed sparkplugs, ignition coil, idle control valve, cleaned TB and intake manifold, all to no avail. I have a pre-cat O2 seonsor which I will attempt to change today, but I don't think it will help - if the O2 is bad, I'm thinking it will misfire all the time or at least at random.

I am about to just throw in the towel and take it to the dealer, but before I get cornholed, I am still hoping that someone can help!

 

Have you even checked your spark plug wires for broken/melted insulation? Once a plug wire gets grounded or is worn then the "fun" begins.

 

The spark plug wires all look great. I think the PO changed them, along with the spark plugs, quite recently, but I figured may as well change the spark plugs...

 

Ok, now are you aware there is TSB regarding the proper routing of the plug wires; otherwise, the engine will suffer misfires? Another point of interest is the cam sensor, which is located in the distributor. If it or its pigtail are damaged, hilarity will ensue.

 

I am not aware about a TSB on the routing - mine are routed as per manual. Do you mind posting a link or diagram?

I don't think I have a distributor?

 

I had a misfire as well. My Plug wires "looked great " too ( Nice Blue NGK's) I changed them out and discovered one that was broken inside one of the boots. Once the new Bosch wires were installed the misfire stopped all together. Before you go bring it to the dealer spend the $ on new wires , especially if you don't know the last time they were changed.

 

I will change the wires, although honestly I just don't see the science behind an idle misfire because of bad spark plug wire - wouldn't that make it misfire all the time or randomly, not just at long idle?

Also, just did a small test - it turns out that reving the engine out of gear will not fix my misfire problem, only when it's driving down the road and flooring the gas pedal will do the trick...

 

Another question - anyone knows which sensor is responsible for alerting for misfire? I'm thinking, since I get no codes or CEL flashes when it happens, maybe that sensor is bad?

 

Did you stuff that oxygen sensor in yet? If not, get that done and see what happens.

 

Not yet, as expected I'm having a really hard time getting the old one out

Also, changed the spark plug wires and the other ignition coil - still misfires.