You probably wasted some money replacing the cops. If you can find someone with a good dso (scope), you can test for bad plugs before you remove them, but unless you plan to get rid of the truck, you are going to have to replace the plugs at some point. How many miles on the plugs now?

If you replaced the cops and boots, a bad plug is highly likely, but test first.
You could also have a bad connector at the cop or fuel injector, a bad fuel injector, a bad wire to an injector or cop, a bad driver in the PCM, etc. All of these things can be tested. Once you collect some data, locating the problem is usually not very hard. Remember that DTCs are only a guide as to what the problem might be based on a symptom. Testing finds the cause of the problem.

 

More of a misfire feel to it, it occurs the worst at 40 -55 has a bad sputter and shakes the truck and also when your want to go up hill from a stop it will just spit and sputter really bad. It's just wierd non of the shops are getting codes, do they need a certain scan tool?

 

David_B - Thanks! In this instance swapped meant, swapped with the COPs other cylinders (not replaced). The boots are new. Plugs are original so waaaaay over due. When I read OP, it was very much like what we are experiencing and curious of his outcome in case it is not the plugs which it does not seem to be in his case (yet). Offer the additional information to possibly provide additional detail that might help us both get the correct answer.

 

In your case, replace the plugs. I would not even attempt to look for a problem with 169K on the plugs until the plugs are replaced. Some items, plugs, air filter, fuel filter, pcv valve, etc., are maintenance items. Other items, cops, fuel pump, etc., are repair items. Replace maintenance items on a time/mileage schedule. Replace repair items when they fail. If you still have a problem after replacing the plugs, post back.

 

DTCs are only an aide, NOT a description of the cause of a problem. Testing is needed to isolate the actual cause of the problem(s).
Your symptoms do suggest a misfire is likely. There are a lot of things that can cause a misfire. Besides a bad cop or plug, you could have a bad fuel injector, a vacuum leak, a broken or shorted wire on a cop or fuel injector, a bad driver in the pcm, an egr problem, a MAF problem, etc.

Yes, they do need a specific type of scanner. They need to be able to read live data. They also need to have a scope so that they can look at the actual signals on the coil and fuel injector signal wires. The scope will allow them to look at the current ramps on the coils and fuel injectors. It sounds to me like you need to find a better tech to diagnose your problem. Someone who knows how to do the actual testing, not just look for DTCs and make guesses.

"Guessers" can get real expensive, are frustrating, and take a lot of time to resolve problems.

 

I don't think '99 - '00 will show a code during a miss fire. At least mine doesn't. No codes when mine blew 3 plugs out at different times. The computer actually operates in OBD 1.

 

I understand. I try to get people to not rely so heavily on codes even on OBDII. The tests that I suggested are still valid whether OBD I or OBD II. Depending on the scanner used, some live data can be seen with OBD I and, with a scope, all of the signals from the PCM can be observed. CKP, fuel injector, cop, etc. control signals can be observed, and with a DMM, circuit integrity can be tested. Powers and grounds can be tested. Testing results in a fix.

 

I don't believe '99 shows misfire data either. I had to do a power balance test with a scanner to find mine.

 

Here is one test for looking for a misfire. Disregard the fact that it is OBD II. All of the codes have been erased so they are not available. This test is valid for all vehicles with COP ignition as long as you identify the coil power feed. This video identifies a spark problem. If all cops and plugs are OK, then move on to other areas like fuel, vacuum leak, MAF, etc.