P0303 Code

I'm with you on that. Weird problem. Hard to see why it ran fine on the test drive, but I am not familiar with injector issues.

 

If it keeps showing miss on cylinder #3 it must be something with that one cylinder, new plug and coil, good compression, assuming wiring to coil is good that leaves the fuel injector or wiring to injector, possibly a valve with not enough clearance, engine warms up valve stem expands so valve doesn't quite seat when it cools stem retracts and valve seats?

 

So my problem still persists on start up after sitting for a few hours. Will idle rough for about 20 seconds, or until i give it throttle.

Been working out of town for the last few weeks but got a chance to come home early this week and decided to pull the plugs to see how they looked.

Cylinder 3 is the right plug



It doesn't look "washed" to me. Also did not smell any different than Cylinder 2 on the left. These have about 500 miles on them.



Just for kicks and giggles, here is what my OBD2 reader is showing at idle and cruising at 70






I still have a hard time believing that its a leaky head gasket, but the scenario of sitting, coolant sits in cylinder, misfires til coolant evaporates, runs fine is still a very good possibility. Just not seeing any smoke out of the exhaust.

I guess im just going to have to bite the bullet and treat it like a head gasket and tear it apart. Just can't imagine the feeling id have if i did that and it was fine.

 

some 3rz engines can crack like this and cause a P0303.
The exhaust valves are the smaller valves.
They run much hotter than intakes and that is "normal".

 

Sounds like an injector my be dripping when shut off. Does it small richer then normal for that 20 seconds.
Try starting it after it sits, let the motor run for just 1 second then shut it off. Pull that plug and see if its wet from fuel.

 

I'll give that a shot this evening. When I looked down in the cylinder you could tell that the piston looked wetter than the other cylinders but did not have a coolant smell.

 

Think it's possible to swap 3rd injector with 1st without destroying the o-rings ?

 

It's a gamble. Depends on how old they are. I've done it before and gotten away with it.

 

Coolant on the plug. RIP head gasket.

 

At least you figured it out!

 

that is true. just not what i wanted to find out. hahah

 

I got a P0303 code last week w/ the check engine light on, truck was shaking in idle and slow speed, after warming up and driving for about 10 minutes prior. I ended up replacing all 6 spark plugs (3.4L) and 1 ignition coil for cyl #3. Start up fine earlier, but problem resumes after I parked at the store and start up again (no check engine light this time but truck was shaking the same as before). What are some possible problems and solutions down the chain? Vacuum leak? Fuel injectors? etc.

 

You should also have a P0300 code.

When my P0303 code popped up, I resolved it by replacing all of my injectors with remanufactured ones from Motorwest in Canoga Park, CA.