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Hi all I’m creating a new topic to carry on from my now solved misfire issue. During the course of my diagnosing my buddy and I decided to do a compression test on Cylinder 8 as the computer was identifying it as missing. We also decided to investigate Cyl 3 as it has had a misfire in the recent past .We looked at the spark plugs on cyls 8, 7 4, and 3. All but 8 appeared normal but on 8 we discovered burned oil and damage to the electrode. When we did the compression on 8 we just pulled the spark plug for 8 and disabled the fuel pump before cranking the engine. With the spark plugs on the other cylinders and ignition system active the engine stumbled during the test. We got 160 on that test. When we tested cyl 3 we pulled just that spark plug but we disabled both ignition and fuel that came out to 160 as well. Now granted I didnt do the test correctly but for a dry test I feel that those are pretty good numbers. So Im kinda stumped on the oil issue. I changed the plugs at around 162k and didnt notice anything unusual about the plugs to me. I did an oil change at 160k on miles and the truck is at 164k now and I had to add about 2.5 qts. Im wondering what your thoughts and opinions are. Also we are not noting any oil/coolent mixing or unusual exhaust smoke. My buddy did note some oil on the walls of the intake by the butterfly.
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I am inclined to suggest a leakdown test. A damaged electrode is usually caused by foreign debris in the cylinder. Really, do a cylinder leakdown test on 8, see what you come up with.
If #8 cylinder is burning oil the residue on the plug can overheat the plug and cause damage to the electrode. There are many causes for the problem such as worn or stuck oil rings (would still have normal compression) worn valve guides or valve seals or an intake manifold leak.
A quick test for a manifold leak is to remove the PCV valve and hose to the air filter and plug the holes in the valve covers. Bottle corks work well if you can find the correct size. Start the engine and remove the oil fill cap and place the palm of your hand flat over the oil fill hole. If you feel suction on your hand there is a vacuum leak. If you feel nothing or slight pressure there is no internal vacuum leak.
The next step would be to replace the valve seals on that cylinder. There is no real way to test them.If the plug still fouls at least you know you have covered the basics.
I appreciate the input wise. Ill do that test this week. I dont have an air compressor or id do a leak down test
If you have oil inside the lower area of the intake then the lower intake plenum gasket is blown. it is still a good idea to cover all the bases by testing everything but 2nd gen rams are notorious for the intake prob. issues with # 8 cyl /plug are usually evidence of this as well as the oil inside the intake. if you do the intake repair get the upgrade kit from hughes engines. the kit comes with everything needed and will prevent the prob from happening again.
Well I went to remove the PCV valve and snapped the elbow 🙁 I’ll have to get another valve. I saw a viddeo where if I cap off the pcv side and hook up a vacum gauge to the breather hose to the PCV thatll tell me if Ive got a bad plenum or not as well. Is the truck drivable with the snapped elbow on the pcv ?
Another update it was actually the pcv elbow i broke but I fixed that. Today I capped off the pcv valve and intake line and popped off the “breather” hose going to the elbow. I started and ran the engine and actually felt resistance/pressure out of the breather hose. When I plugged the hose back in and took off the oil cap I didnt feel much there. So I feel at this point that my plenum is actually good
My plan of action now is to of course replace tghe spark plugs. Im thinking NGK but I have also been looking at the Bosch Platinumn plugs. I also plan on removing the valve cover to check for rocker tightness and also see if I could pinpoint the oil burn (checking drainback holes, valve seas/guides) my next question is are the seals and guides replacable on my truck? Short of redoing the entire head?
The valve seals can be replaced with the heads on the engine but will need to be removed to repair the guides.
Hi Again all sorry for the silent spell. I took the truck to the shop today and had them run a compression test and leak down. Turns out #8 has 125 on compression. They also said its the intake going out thats causing the oil issue.
Yea, fancy plugs won’t solve an issue like that. In fact, I’d recommend the plugs the manufacturer put in there in the first place. Champion I believe. Looks like it was a compression issue as I had suspected. The leak down should reveal the real culprit. Likely worn rings or a cylinder issue unfortunately. If that is the case, I’d recommend at the very least a reman long block, a complete engine replacement would be best for long term use. I suppose it really depends on how long you intend to keep the truck and how you intend to use it.
Good luck and keep us posted on how things turn out.
Hi Eric Im sorry I just saw your post and it looks like you were posting as I was posting. The shop I took it to says its the intake and in recent days I’ve been hearing a whistling noise from that side of the engine which to me verifies the intake issue. Gonna actually start a new post on this because I figure its an oppurtunity for me to make a couple of DIY videos. Not as great as yours but still. Kinda wish I could bring the truck down to you and let you toy with it but it sounds like ya got a lot more fun projects.
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