unplug both sensors? Also, by unplugging, won't it through a code?

 

Have you checked and rechecked all of your connections to ensure they are free of dirt and grease? Also, have you thoroughly inspected the distributor cap and also the cam sensor for cracks or other damage?

Unless the spark plugs wires are not properly routed or improperly insulated, I'm betting there is a problem with a connection or fracture in a wire harness (such as the pigtail of the cam sensor) because the same codes are constantly being thrown.

 

Gary-L - yes, I have, with my OCD (LOL) numerous times. The spark plug wires are all routed individually away from one another and wrapped in convoluted tubing.
On Monday, I swapped plugs..1 with 3, 6 with 8 and 2 with 4. Cleared codes and hard reset the ECU. I drove it to work today. Brought my laptop with me and it shows P0308 as PENDING.

REEEAAAL dumb question here....I recall, after switching out spark plugs for the 3rd time (2 sets of Autolite's) now using Champion, that on a few of the Autolites, the crush gasket was not on the plug when I pulled it out. The Autolite crush gasket screws on so I just didn't screw on a crush gasket on the new plug. For the Champion plugs, the crush gasket/washer is actually on there and doesn't physically screw off. Here's the dumb question...If I screwed in a Champion plug with an existing washer on it into a hole that has a stuck crush washer could THAT cause a misfire by not having the plug all the way properly seated in the head?

 

Wouldn't hurt to pull your plugs, and check to make sure you don't have any extra washers in there....

Still have your heat shields? Make it easier to inspect if they were gone. (and they don't really serve much purpose in any event.)

For the O2 sensors, just unplug the one you want to test. Yes, it WILL set a code. (eventually)

 

Yes HeyYou, the heat shields are still on there.

Are they easy to remove?

 

Question 1:
Are you running Autolite plugs or Champions? I tried Autolites in my 2nd Gen and it hated them. It ran like a dog and threw several misfires, most notably on #5. When I reinstalled the Champion plugs, it ran great. I later learned (most) users here, who have Autolites installed in their engines are also running a tune. Just food for thought.

Question 2:
When I bought my 2nd Gen and ended up rebuilding the engine, I discovered three of the injectors were completely plugged up with debris on the inlet side. Upon teardown, I also discovered dirt and debris built up in the fuel rail. I would recommend removing and inspecting the fuel rail as well as the injectors. Bear in mind that if you choose that course of action it will be wise to replace the upper and lower injector seals. Cheap insurance, so it's not an unbearable sunk cost.

Also, just to note, you've poured over the wire routing several times. That's fine; however, what about a thorough inspection of the cam sensor, including the pigtail. I'm talking pulling the sensor and completely cleaning it with a degreaser before inspecting it for cracks or breaks with a magnifying glass or jeweler's glass. Said inspection would include the insulation on the pigtail as well as the connectors. As I said a while back, my truck threw misfires on a few cylinders when I buttons it up, and when I inspected the electrical portions I found that dirt and grease impeded the performance and resulted in misfires.

 

Thanks for the info. I got home today from work with the p0308 still pending. I removed plugs 2/4/6/8 and removed the heat heat shields too. Couldn't truly tell if there was a stuck crush washer in the head? Since I was having repeat issues with cyls 1/2/8, I decided to take off the washers on the champions. Put some anti seize on threads. I'll see what happens...Also, I replaced the injectors not to long ago.

 

OK, anti-seize on the threads won't make a difference in performance. It's good practice because it prevents plugs from rusting to the heads.

Since this problem seems to have manifested after you recently replaced the fuel injectors, then it is possible there is an issue with A) the injectors reporting the misfire; B) the injector harness and/or plug of any affected injector(s); or 3) a combination of the previous two.

 

The problem was there before I changed the injectors, which is why I decided to change them out. Basically, it's plugs, wires, dist cap, rotor, coil, cam sensor....all have been replaced. The one time that I replaced the plugs, with newer Autolites, the CEL went out immediately, but eventually came back again. I'm really leaning towards the connection between old plugs and new champions. I'm thinking the crush washers are still stuck on the heads for those particular cylinders. Having a double washer or triple was wreaking havoc by not having the plug fully seated in the head...just my theory. I'll drive truck to work tomorrow and see what happens. Thank you again for your insight and feedback.

 

Ok...a co-workers husband owns a garage. He performed a compression test and leak down test and it passed with flying colors. He hooked vacuum gauge up and it's drawing high vacuum 27hg. He said something is causing high vacuum...blockage? He said if he was troubleshooting it further, he would take the manifold back off...thoughts?