Hello,

Recently purchased a 1997 Dodge Dakota Sport 4X4 5.2L (172K miles) and it continues to throw P0307: Misfire Detected → (Cylinder 7) codes.

I feel like I've done most all the troubleshooting I can think of and wanted to see if I was missing something

I have:
Replaced the spark plugs
Replaced spark plug wires (and coil wire)
Replaced Cap and Rotor
Swapped injector on cylinder 7
Compression check on cylinder number 7 (looked good at 110)
No Vacuum leak - checked on the intake (spraying brake clean near intake on cylinder 7, no RPM rise)

The old cap and rotor did not look too hot so when I swapped that I was confident it would fix it but no luck. After every change I cleared the code with my OBD tool.

Also, when its cold, it sometimes will die after putting it in drive/reverse and very light throttle.

Could it be the ECU? Anything else I missed diagnosing?

Thanks for you thoughts

 

110 is on the low side.... (minimum is 100....) What do the rest of the cylinders look like?

Pull the air filter housing, and crack the throttle wide open. (engine NOT running....) Have a look down into the intake, see any oil pooling in there?

 

Thanks for the reply.

So I cracked the throttle blades and looked inside and it looks damp or slightly wet with oil (of course carbon as well). Not sopping, dripping wet, but a shine or a gloss of oil all around inside the intake.

I also redid the compression check on the driver side. I was originally wrong on cylinder 7 and its a little worse that I thought.

1 - 120
3 - 145
5 - 150
7 - 105

I'll do a compression check on the passenger side tomorrow as those numbers sort of scare me.

I plan on pulling the intake, checking for any gasket tears/leaks and im also considering taking off the head to look for burnt valves, cracking of the head and replace the head gasket.

i also forgot to ask, is there a possibility that it’s the crank sensor? Wouldn’t it throw a code specific to a crank sensor fault along with the misfire if that was the issue?

Let me know if i'm missing anything....

 

Yeah, you are out of spec. Not surprised you are getting a misfire there. Do you have the ability to do a cylinder leakdown test??

 

No, don't have a leak down tester nor any smoke tool.

The fact those numbers are so low, I think I will definitely take the head off. Maybe get it magnufluxed, check the valves and gasket

 

If I had a leak down tester. That would be able to determine if's a head gasket issue vs valves would it? It would just verify that the cylinder is leaking from SOME point... right?

Harbor freight has a cheap one lol

 

Leakdown test will tell you where the compression is going. You will be able to HEAR it. (assuming you don't have a lot of competing noises in the background.)

 

Check the other side of the engine to be sure.

What you can do it remove the shrader from your compression tester, then chuck it to an air compressor. (Assuming the shrader is removable). All a "proper" leakdown tester is, is a manifold with 2 opposing gauges. One measures inlet pressure against an oriface, coming off a regulator (usually set to 100psi), while the other measures pressure on the engine side of that oriface.

But if you're not worried about a percentage or differential pressure, just chuck up the hose with the shrader out, and see if it's coming out the intake manifold, dipstick tube, or if the radiator hose starts gurgling.