My 96' was throwing the same codes and number 4 kept missing each time the codes were cleared. This occurred around 120,000 miles and running sluggish and rough. Come to find out, the valves needed some major cleaning. I also had all of the hoses replaced. The cleaners you used burn off before they reach the back valves. So, in other words, your valves may be sticking. My Bumble Bee runs like new.
Ok, I have the exact same situation it looks like.
After messing around for a while and not making any progress, I took my truck to the independent Euro mechanics so they can have a quick look over and give me their opinion, thank God they are around the corner from me minutes away and I was able to drive there. So I gave it a shot, the compression test cost me a few bucks even though I could have done it myself. In a sense I am glad I am getting to the bottom of this.
So the next day, I get a call and they ran a compression test which revealed low compression on Cyl. 4. So I have an internal problem now. The truck runs and drives, it is just really sluggish at around 2 - 3.5 rpms. This problem seems to have happened overnight and I am thinking the problem is in the heads, maybe stuck valves. I don't want to know what it looks like under there, maybe the previous owner ran 87 octane, and it was just a matter of time before the damage was done.
Is there any way I can clean the valves with an additive or something before I start digging deep into the engine and my pockets, should I change the oil and add some compression booster or some kind of engine treatment. I ran a can of seafoam thrrough the intake, should I do a can in the crankcase? Let me know what you guys think. I do have a crack on my exhaust manifold by cyl.4 - would that cause the problem, when it is running slugging it backfires through the intake and pops? It feels like I am running without a spark plug. Although it starts right up smoothly. Thanks for the input in advance.
I have cleared of my CEL and it hasn't returned.