The valley pan gasket on my truck was leaking oil that's the only reason I mentioned it. The old valley pan was cracked and bent where someone installed it poorly then covered it up with RTV. Once I replaced it the leak went away. However since the valley pan seals the lower intake manifold to the head if it isn't sealed right you might have a small leak and when the engine is under load it opens up that leak thus allowing more air into the cylinder throwing of the air fuel mixture causing a misfire.

If oil were leaking out of your valve covers you would notice it a bit more and smell the burning oil. Not to mention the sheer amount of oil it would take to cause a problem with the plugs.

Since I didn't have any coolant loss or coolant in the oil or exhaust I knew using a cooling system pressure test wouldn't help me out at all. The compression test is useful for seeing how well the mechanical seal is between your piston rings/bore, heads, head gasket and valves. While it's possible the rings could have been failed there weren't any other signs of that eg: blowing blue smoke. That narrowed it down to the head gasket or valves. Since most of the gasket was blown off near the culprit cylinders I felt pretty sure that was the cause of the misfires.

Yeah for whatever reason Rover decided that it was best to use playdoh to make their engine blocks and the will strip and gouge very easily if you aren't careful. Though on the other hand re-tapping a head bolt is very easy as compared to an iron block.

 

I figured this out. I did a sea foam treatment today and the problem got so bad I couldn't get down the street.

It was the damned vacuum hose on the throttle body. I gooped silicon on it. An hour later my problem was cured.

 

Very interesting.

So your symptoms were a bad misfire?

And it was throwing a code for the misfire?

 

Right. On three cylinders. However, after I did the sea foam I was getting on four cylinders and it wasn't just on hard acceleration as before, it was on basically any acceleration. The fact that the change was so abrupt caused me to think about that hose. That was definitely the problem. I went for a drive again after putting silicon on it and got no misfires.

 

And then I suddenly got more misfires. I checked the hose and it is sealed. I have a Rover so of course I keep a code reader with me. Same cylinders and multiple misfires. It was shifting to 2nd gear at 65mph on level ground. So pissed... I just floored it for an Italian tune up.

So I reset the codes (while driving; no stop, no change of conditions; same road; same speed) and all of the misfires stopped. Explain that one to me...

I'm beginning to think that most of my truck's problems are in its head.

I did order a complete set of oxygen sensors so I can hopefully quit worrying about those codes. Tightened up the exhaust today. Changed the oil. Said a prayer.

 

You should post the codes your truck is throwing. You may want to start your own thread.

 

Good point. I'd come to believe this was my thread! Haha. When I put the new oxygen sensors in, reset the ECU, and see what pops up, I will do just that. Thanks for the gentle suggestion; you're right.

Best,

Charlie V