Well, this doesn't just belong to the 1st Gen durango forum even though that is what it is happening on. This is issue with my 2000 4.7L engine, getting a P0307 cylinder 7 misfire CEL. So, I went with the spark plug (replaced them), the coil on plug (replaced it), cleaned the fuel injectors and still got the misfire. Took it to the mechanic and they tested. Found that the fuel injectors where working, and getting spark but found that compression on cylinder 7 was 50 psi. So they recommend an engine replacement. I told them I replaced the engine 40K ago, they didn't realize the engine was replaced, thought the engine had a lot more miles on it.

They tell me it it probably piston ring or burnt valve. Both look like it is an engine replacement or major engine work to fix it. I did take the valve cover off and the rocker arm is still in place. Was hoping for some way to salvage this, is it possible that a bad lifter could cause a misfire (low compression)? Or would a faulty llifter just prevent the valve from opening all the way (or failing completly and causing the rocker arm to fall out) and not have anything to do with compression? Thanks for any thoughts on this.

 

Dropped valve seat would do it. See if you can get your hands on a bore scope, and take a look inside the cylinder.

 

Ugh... if it is dropped seat sounds like it will be a very expensive fix

 

Replace the head...... Cheaper than a motor.

 

I just replace head gasket on my 4.7L and it really easy to do on this engine. So replace the head. The best way to save money and time.

 

Ok, looked at some video's and think I can do this. I am a little nervous about the timing, maybe if I only do one head it will be easier but not sure on that. Just need to figure out if it is valve or if it is piston issue. Don't think I'm capable of fixing if it is a ring.

 

4.7 is known for various head issues, not really seen problems with bottom ends usually.

 

Don t worry you will always find somebody here to tell you what to if you are lost. You just have to build a tool to loose the camshft from the pinion.

 

Ok, so a tool to remove the camshaft... any tips on that? Also, wanted to only do the one head. Any tips on keeping the timing chain in place while replacing the head? Getting close to tear into this thing

 

for the tool you need a flat iron and 2 screws I will show you a photo of the tool that I made. with it it is much easier to unscrew the pinions of the camshaft and to tighten them. for the timing belt. the main one is to call the crankshaft well and then the 2 pinion where it is written "v8" must be horizontal. before dismantling you must put the pulley on the mark at the bottom right of the engine.