Exactly what I'm talking about. The volume and speed of the incoming air going thru the air box, throttle body and into the intake manifold is created by the vacuum inside the plenum. Now you are telling me a small amount of the same incoming air in the air box magically changes from incoming air to out going air at the hose connection on the air box?

I never studied physics but good old everyday common sense tells me you're wrong.

 

Where is pressure lowest? In the air box, or the plenum? Air flows from an area of higher pressure, to an area of lower pressure. It doesn't have a choice. You can verify that I am indeed correct by reading the description of the PCV system in any of the service manuals available for download here. In the 96 manual, it is on page 25-17. here is a direct quote:

Flow is from the air box, to the intake.

 

I have a 96 1500 5.2l with 120k. After reading this sticky on here I replaced the plemun gasket, plugs,cap,rotor,wires,thermostat. Did a coolant flush, changed oil and filter. Put is back together fine, the truck started right up and sounded much better. No shaking or mis-firing. I let i warm up and took it for a drive about 10 miles and it ran great. This morning while going to work I got the check engine light on while stopped on a hill and the engine started to idle rough. It started to misfire again about 45mph but not nearly as bad as before. Pulled into the parking lot and put it in park and low oil pressure came in. I checked the oil and the level and oil condition was fine. Started it back up and oil pressure was normal. check engine light on with a code of 43 again. I am thinking pre cat sensor and cat for the code but the oil pressure thing has me worried. Any ideas? Thanks

 

Why doesn't everyone take mechanical engineering classes to learn about head loss?

Edit: High School Physics class covers this.




Did you have battery negative disconnected for all that maintenance?

I'd try that now and see if this condition comes back again, just for kicks.

Did you replace the O2 sensors at that time? If not, then I'd actually just go ahead and say to change BOTH of them as they are most likely the original ones.

Your oil pressure, it's constantly reading zero now, every time you go to restart and warm up?

Have you searched for other similar threads here? There are some current ones going where people doing through very similar symptoms would chime up.

 

Ya neg was disconnected and when the check engine light came in the first code I got was 12 (which is batt was discoed) the second one was 43. I did not replace the O2 sensors and that is what I am thinking now.

The oil pressure is totally random, but it ready normal or none.

 

At this point, I'd suggest replacing both O2 sensors. If you have time, search around for NTK brands.

There is hit and miss performance on Bosch brand. Most local parts stores will have those.

Get a new oil pressure sender.

I recommend everyone when doing the plenum gasket repair or intake manifold swap to just replace the O2s.

As for the oil sender, you'll at least have a 2nd one and it may/may not rule out the oil pressure. I'm presuming oil pressure was fine PRIOR to all this work. Or did you also mess in the bottom end, pulling the pan off? Any chance of dropping something in the top end?

 

I drove it home from work today and the misfire progressively worsened on the way home. I will replace both O2 sensors. The oil pressure was fine at first until the first stop sign when it went dead. The oil pressure was fine prior to this and I did not pull off the oil pan or do anything on the bottom end. As for dropping something in the bottom end, anything is possible but I would like to think I didn't. I am the chief mechanic for large turbines for the last twenty years, so I think I have some good work practices. But it is always possible. Without putting a gauge on, is there anyway I could tell if the pump is pumping oil or it is just a sensing problem? Thanks for the help

 

Getting back to the topic of the plenum pan gasket leak, in the video the direction of air flow is correct. The vacuum below the butterfly throttle valve is more negative than the air pressure above the valve, so a small volume of air is drawn down the air breather hose into the crankcase. From there the negative pressure draws air from the crankcase up the PCV valve into the intake manifold.
I appreciate the remark about how you can have a leaking gasket and not see vacuum in the crankcase. Any test can have false negatives, though it is hard to conceive it being a large leak with no air movement across a failed gasket. If I were having other typical symptoms I probably would disregard the lack of vacuum in the crankcase and replace the pan anyway.
I also appreciate the remark that vacuum at idle seems a little low. I agree. But if the vacuum were due to an internal vac leak to the crank I would expect to be able to measure at least a little vacuum there. I still suspect a small external vac leak and will be doing a smoke test in the coming weeks.
Thanks for all of your input!

 

http://www.****************.com/smf/...p?topic=9504.0

Would this walkthrough be compatible with a 99 ram 1500 4x4 with a 5.9?

 

URL doesn't work. Seem it is censored. Not sure what that's all about.