My 03 4.6 is driving me crazy !! It has a constant miss at all engine speeds. It was running fine and BAM a mis and sputter!! The code is PO307. I have changed plugs, coils and it is still there. I took off the green vacuum hose and used a piece of hose and it isn't the egr valve. Could it be a broken valve spring? I read about a cam follower, what is that?? Please help....

 

P0307: Misfire, cylinder #7 (third from front on driver's side)

Causes could be anything in the ignition system (which you just went through), a faulty fuel injector (suspect not opening, but could be open at all times), or possible base engine problems.

Broken valve spring: Could be a possibility, as could burnt valve or bad cam follower.

Cam follower: We used to call them 'lifters' in the good old days. If one of those is bad, it could be the culprit.

What I would do: Exchange the fuel injector on cylinder #7 with cylinder #5 (drivers side, front). Clear any codes by a code reader, and then drive the vehicle to see what code comes up. If you receive a P0305 (Misfire, cylinder #5) then you know that the fuel injector is bad. If you still get a P0307, then your problem is still with cylinder #7.

If the problem is still cylinder #7, I would CAREFULLY inspect the plugs and coil first for any possible problem (coil open circuit[infinite resistance] or short circuit [zero resistance] with a volt/ohm meter and coil OFF of engine, plug resistance in specifications, any possible spark plug boot contamination allowing spark to go to ground, fluid in the spark plug 'cavern') BEFORE I would remove the valve cover and inspect the cam follower, camshaft lobes, and valve springs.

I'm hoping for the best in this situation, and that it is just something with either the fuel injector or with the coil or plug, and not something serious that will require major repair (broken spring, cam follower, burnt valve).

Good luck with this problem. I hope what information I gave you helps you solve this problem.

 

Just one clarification on the lash adjuster and follower. The follower on these overhead cam engines is comparable to what a rocker arm is on pushrod engine and a lash adjuster is comparable to what a lifter is on the pushrod engine as well. The difference is in their design and how these two components function in unison with the overhead cam. A defective lash adjuster will go soft and can allow the follower to pop off location giving you a dead valve, either intake or exhaust. I just didn't want any confusion in case you find one of these components is defective and you have to aquire a new part. AZ Mr.Bill has given you some great advice. Good luck.

 

Thank you, DYNOTECH, for the vote of confidence on troubleshooting this problem. I could really use every now and then. NOW I know that 35 years of busted knuckles and shadetree auto repair did not go to waste.

I should have known that the cam follower is the rocker arm in an overhead cam engine also. I'll cough that up to Sometimer's Disease (Sometimes I remember, sometimes I don't). Too many non overhead cam engines in my lifetime, I guess.

 

If you read many of my posts you'll see that I suffer from the same disease. I imagine that some here think I'm losing it, hell my wife is already convinced Take care AZ.

 

I have the same problem with mine.. But,along with the miss I have raw gas fume's at exhaust. Could this mean injector is stuck open?

 

sure, an easy way to test for leaking injectors is hooking up a fuel pressure gauge and if it looses all pressure quickly after shutting the engine off then the fuel is going somewhere