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1994 Dakota 3.9L
I replaced the EGR when I bought the truck. I ended up doing the plenum about 6 months later to cure the oil leaking in due to gasket wearing out between steel plenum and alum intake.
I got an egr code a month or so ago so I cleaned it but the code came back right away. I replaced the EGR and its been fine for a month then I got another egr code.I was told to look for soot in the exhaust and I found it. I looked up causes of soot. There are several items. I started with the IAC. I went to clean the IAC and had to remove the throttle body. When I did I looked down into the intake and saw oil in it. This is not supposed to be. I used new bolts and blue loctite on the plenum bolts and followed the detailed instructions to progressively torque it 3 times.
I emailed the people who sold me the repair kit. It is supposed to be a permanent fix. They said the oil had to come from somewhere else. !????
I am replacing the PCV it should be in tomorrow. The current one is newer than the EGR I put on when I bought it.
I have added a small see through filter in the PCV to intake hose so I can see if any oil is passing through that way.
I replaced the air filter and the old one did not have any oil on it from the breather that comes up to the air cleaner from the other valve cover.
There are three other hoses to the intake one below the PCV hose and two on the other side of the intake that are AFAIK vacuum lines.I’d like to know any other possible sources of oil to the intake plenum.
Has anyone had this happen to them?
What could it be?
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When I placed the filter in the PCV line the valve was oily all the way through.
It has 147K+ miles. I suppose blow by could be an issue. I have added Risolone on recommendation a while back. I recently changed the oil. I used a method an Aussie told me about where I drain it and put the dirty filter back on after emptying it, and poured in half the full amount of new oil and some cleaning agent and drove it a bit. Then I drained it and put on the new filter and new oil. That seemed to make it run better, solve the valve noise/knock issue and give me better mileage until the EGR code popped up about a week ago. Mileage has dropped off significantly in the last week.I have replaced the PCV. When I removed the air cleaner I noticed the new filter had left a ring of oil on the top and bottom lid. This makes me thing the previous aftermarket filter was letting oil from the breather get by over the top since it wasn’t sealing. I sprayed carb cleaner and used a paint stir stick and hanger to rub a rag around trying to get as much as I could removed. I am going to replace the breather and put a filter in the hose like I have done with the PCV to see if anything is getting by that way.
If it isn’t it can only be a failure of the plenum gasket. The pictures are taken with the throttle body off looking down into the intake holes.A compression check and a leakdown test will tell you a lot about the mechanical condition of the cylinder bores and rings.
What you could do is disconnect the pcv to the intake and plug the hole to the intake
and let the hose of the pcv vent to the atmosphere temporarily tied up out of the way
to see if the oil stops. If it does blow by if not gasket.I haven’t been here in a while. Sorry to anyone who needed this info.
I ended up by putting a filter in the PCV line and the oil breather hose that goes to the air cleaner from the other valve cover. It turns out there is oil getting through the oil breather which is new. The back pressure from the filters caused a seal leak that went away once I removed the filters. I make sure I get good air filters that seal top and bottom and check them every couple months.
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