Ok. I'm Back

First let me thank anyone who helped me with my broken PCV valve problem.

But here's my situation:

I have a 2004 1500 4.7 non flex-fuel.

I have been getting P0300 errors as well as the error for the slight evap leak.

Took it to a monro shop to get it diagnosed. They told me it needed a tune-up and that cylinder 8 needed a new coil and you should replace them all at once. yada yada yada. didnt have the cash, so I replaced the coils and plugs on cyl 8 and the cylinder directly across from it right away. a couple weeks later I replaced the rest.


I replaced the plugs and coils, as well as the PCV Valve. (thanks for the how-to's in this forum!)

The plugs are the champ copper oem equivelants.

Its got about 80k on it all orig equip.

Its still throwing that code. I pulled the plugs again last weekend to be sure everything is ok and they all looked clean and dry accept 8. It looked wet, prob gas. some shelacking and the electrodes and ceramic cone were black. The rest were white like they where when installed. dble checked all the gaps. cleaned the cyl 8 plug and put it all back together. Still does the same thing. Runs a little rough around 2500 rpm chugs and hesitates a little, still getting decent mileage according to the computer. in fact it went up to 13.5 from 13.1 since I did all this.

I saw that this might be caused by the camshaft/crankshaft sensor or possible bad wire. I am not looking forward to chasing down a wiring problem.

I dont understand why I wouldnt get a p0308 coade if it was just cylnder 8.

Any suggestions...

ps I got the codes using the on off trick

It works.

Thanks

John

 

Could this be an injector problem???
I have a Hemi so I'm not familiar with the 4.7.
Do they have injectors??? I would assume they do as they are fuel injected.
Al.

 

well there is more than plugs and wires that can cause a misfire. Do a compression test on the misfiring cylinder, then on all the rest. If there is low or no compression in a cylinder it will not fire. Burnt valves, wiped cam lobe ect among other things.... can also cause a misfire. It also could be a faulty injector as Abarmby said. You really need a scanner that can read injector pulse, resistance and voltage drop.

 

Yep John, it's time to do a compression test on #8...

 

Thanks for the input.

So,

Should I bother looking into a wiring issue with that cylinder, 02 sensors, or vacuum leaks? Will I be doing any kind of damage to the ingine by driving it until I can isolate and fix the problem?

Also,

How hard is is to do a compression test? Never done that.

 

O2 sensor isn't going to help you out here because it wouldn't cause a misfire on one cylinder. Before you do a compression test take 2 mins to pull out the plug and see if it is getting good spark. The BEST and safest way to do that (if you dont know) is to get a spark tester plug. But if you don't have one of those you can ground the spark plug (be careful) and see what the spark looks like. It should be nice and bright and blue, not dim and yellowish. Go from there, if there is no spark you know where to start. Let us know.

A compression test is easy to do, first you need a compression test gauge though. Someone you know probably has one or you can buy one for about 30 bucks. Google "Compression Test" and you will find it. I don't have time right now to type the process sorry. Good luck

 

You can get a noid lite to test your fuel injector pulse to see if the injector is firing but I would say itis stuck open since the plug is wet. Once you change the injector and spark plug make sure you change the oil. It probably has dumped fuel in the oil if it has been leaking for awhile which could cause other damage. SSounds stupid but if you smell the oil on the dipstick see if you can smell fuel if you don't it does not meen this is not happening just not a lot of fuel in the oil which is a good sign.

 

Ok.

That sounds pretty good.

Kinda afraid of a compression loss issue. Sounds complicated to fix. Compression loss means valves, rings or head gasket, right?

So, I'll pick up the spark tester and check for spark this weekend. What is the niod thing to test whether the injectors are firing. Is that an expensive tool? Is a sticking injector hard to fix/replace?

I also was also told I could check the injectors by switching the injectors between cylinders and see if the missfiring cylinder moves. Any thoughts on that method?

If I dont have good spark, what then? I am accostomed to the "old" cap and rotor system. This coil over plug wiring scheme isnt quite as straight forward. Is it hard to chase down bad wires? Can you get new sets of wires? I am reluctant to start taking all the chase tubes off these wires as there seems to be a lot of them...

Sorry for the excessive questions. I am kind new at this (in case you couldnt tell)

Thanks again
John

 

Yes on the compression question also camshaft is in that list as well.

A fuel injector noid light is just that. It is a small light that plugs into your fuel injector connector and flashes every time the fuel injector is supplied with power to make the fuel injector squirt. It should light up nice and bright. Or you could also do what you friend said with switching the injectors but that is more work than just pluging in a noid light. But switching the injectors would pretty much rule out a bad injector itself if the problem persists after you switch them.

If you have the coil on plug system you dont have spark plug wires. The coils just have boots that connect to the top of the spark plug. If you dont have spark then its either the coil itself or a wiring issue. You could also try the same method with the coil as you could with the injectors by switching them with a known good coil. But if you just replaced it with a new coil it SHOULD be good but thats not 100%.