Good morning everyone,

I have a slightly different oil problem. I'm running 10W-40, at start up, with the engine cold, the oil pressureis slightly above 40psi. After driving enough to get the engine at temp(180 degrees), the oil guage is slightly below 40psi. The guage does fluctuate with engine rpm's. Now my problem, with the engine warm, at idle, in gear, and me pushing on the brake, my engine rpm's drop to just above 300 and my oil light comes on even though the oil guage didn't go lower. If the truck is still not fully warmed up, there is no problem.

I just completed the intake plenum cover replacement and changed the thermostat down to 180 from 195. I used the replacement cover from Hughes. I no longer have the oil sucking problem and the truck feels stronger. I ran the truck around town and then changed the oil and filter. I was hoping this would help with the oil light coming on. It didn't. The oil light came on about three days after I started driving the truck again..

I was running 20W-50 prior to the intake plenum cover replacement because I was hoping it had somenthing to do with it. The thicker oil lasted longer, but it toowould eventuallygive an oil light. I thought I smelled gas in the oil. I could be wrong. I'm at my wit's end trying to figure out why my truck is doing this.

The engine also clatters at startup after running it at temp and then shutting it down for twenty or thirty minutes. It doesn't clatter if I start it before then.

I'm wondering if I might have two problems. One, the oilis getting thinned out. Two, the oil pump is worn. I have 139,000 miles on it.

Here is a stray thought, If the O2 sensor was malfunctioning, would that cause excessive gas to be sprayed into the cylinders and perhaps work it's way into the oil? My milage before the intake plenum replacement was 14mpg highway, down from 17mpg. I haven't had a chance to check it post plenum yet. I'm not getting any codes. I did replace the pre-O2 sensor when I had to replace the cat about six months ago.

What do you guys think?

 

I think your problem is your idle speed is too low to pump the oil properly. It's probable that your idle speed motor hasn't adapted to your fixed intake.
If your plenum is leaking your engine is getting too much air and your idle motor will close too much to try and restrict your air intake.

try removing your IAC motor and cleaning the gunk off it. (rear of throttle body) and disconnect battery for 30 mins to clear PCM (engine computer) memory. It may take 500 miles for you computer to relearn now that you have fixed it up.

 

Thanks for the reply rabbler. My IAC was gunked up. I cleaned it and ,for good measure, since my truck was stone cold, I pulled and inspected the spark plugs and both O2 sensors. The plug and sensors seemed okay. I cleaned and regapped the spark plugs. I have just replaced the intake plenum pan a couple of weeks ago. I am no longer loosing oil. I've included a pic of one of the spark plugs.
Aubrey has posteda similarproblem that I'm having:

I'm still having an oil issue and I don't want to go throwing money and random parts to try and figure it out. My oil light still comes on after highway driving but I now know it's not due to low RPMs. The light came on yesterday and the RPMs were slightly higher than when the light would come on before. I have the clacking at start up until the pressure comes up. I've only recently had this. My pressure on the gauge looks no different than it ever has. And I am now getting a slight clacking noise (not spark knock) just before a shift. When I was on the highway Friday it made a noise similar to it when the gas pedal was in a certain spot.

After searching this forum, I've settled on the IAC as my low RPM problem. I'll change that out next week. I still have a clattering at startup after the engine has run enough to get hot. It's as if the oil is so thin it won't stay in the enging and is draining into the pan. I went from 10W-40 to 20W-50 to see what the effect would be. The 20W-50 will eventually do the same thing. It just takes longer. I'm open to ideas.

Thanks,
Scott

[IMG]local://upfiles/53832/048417321CD8484CB696C88EF9606407.jpg[/IMG]

 

Scott, what year is yours and is it the 5.9? Yours sounds almost identical to mine. That clatter at startup and other things but I haven't tried the brake part. This only started after my plenum gasket fix too so I wonder if there's something related to that. Did you do your gasket replacement yourself or a shop? I had the dealer do it since they should follow their recall procedures and figured things would get done right. I'm at a loss and am worried I'm going to seize my engine eventually.

 

Mine is a '96 360. I did the plenum myself. The clatter existed before I did the plenum repair. No problems so far from the plenum as far as I can tell.
A friend of mine suggested I tweak the idle speed rpm's up to 650 or 700 from the 500 it currently sits at before it is hot from highway driving. I'm not to sure how to do that. If someone has the procedure, could you send it to me? Thanks in advance.

Scott

 

I don't believe that you can increase the idle speed as that is one of the functions that the computer controls.

Is your clatter coming from the timing chain or lifter/rocker arm area of your engine? I would make a guess that it is your timing chain that is making the noise. Mopar makes a replacement part that eliminates that issue, but you have to pull your timing chain to install it.

 

You are correct about the idle being controlled by the PCM. I figured that out after I had posted that reply. So now I have understand what input or inputs to the PCM are causing the IAC to drop the RPM's to 300. Or it could be the IAC. It is heat related. Once the engine is at temp (180) the idle rpm's with the truck in drive drop to 300 from 500. Also, in park, the rpm's drop when I turn on the AC.

The clatter is coming from the lifter/rocker area. It happens at start up after the truck has been run enough to be throughly heated up. It's as if the oil is too thin and is draining out of the lifters. If the engine is cold and Istart the engine for a minute(clatter until oil pressure comes up), shut it off, then restart it(no clatter). I'm running 10W-40 now after the the plenum pan replacement.Before, I was running 20W-50.The clatter would eventually come back after an oil change. It just took longer with the thicker oil. I checked the spark plugs (see pic) and they are not oil or gas fouled.

I just had the timing chain and sprockets replaced about three months ago.

If anybody has an idea I can use, I'm all ears.

Thanks,

Scott