I just looked at the 4.0L valve cover which will be going on my 4.2/4.0 combo and I noticed the PCV valve was clogged with gook (on the inside of the valve cover are three screws which allow the PCV casing to come away from the valve exposing the PCV Valve itself). Can the valve:
Be cleaned satisfactorily?
or
Be replaced with a new valve?
I seem to remember reading that these cannot be replaced but not sure either all of them are like that or only some. Looks like it was made to as it has access to the inside.
Oh, Ok.. It finally clicked. The rear valve on the valve cover is the PCV (Positive Crankcase Ventilation) and the tube that goes to the intake manifold is the CCV (Crankcase Ventilation) Tube. Is that right?
I was at Chrysler parts today and asked them what the tube was called and they said, with a straight face, "the tube that goes between the PCV valve and the intake manifold".
There's no valve in the CrankCase Ventilation (CCV) system, the rear tube is just a manifold vacuum tube with a metering orifice to limit the amount of vacuum applied to the crankcase (See _Chilton's_ `84-98 Cherokee manual, Sec. 4-2 "Emission Controls" for description and testing method). The front tube is a fresh air breather and comes in two parts, Left Vacuum Assembly and Right Vacuum Assembly.
Follow the link Mike gives below for the Mopar part numbers, or read the following from a different thread 9 days ago for the Balkamp part numbers. Shop around, you might save a few bucks -- and I'm betting that they are all Balkamp parts anyway. I paid US$41 for all three parts at NAPA, the rear assembly only cost US$11, so you have to decide what your time is worth.
You are dealing with 2 totally different engines that 'breath' in 2 totally different ways.
The 4.2 L engine uses a PCV (positive crankcase ventilation) valve from the front of the valve cover that sucks through the carburetor base plate. Along the way there is a T in the line for the Charcoal Canister which is the gas tank vent. This PCV suction is balanced to have the canister kick in when ported vacuum comes up high. (at speed basically)
The intake for the engine on the 4.2 comes from the air filter and goes to the rear grommet. That is just an open hose that sucks filtered air.
The 4.0 engine uses a CCV valve (closed crankcase ventilation). This is a small hole in the rear grommet of the 4.0 valve cover with a small plastic tube in it that goes to the intake manifold. This small hole is 'metered' so a certain amount of suction is always there. The hole can be cleaned out with a paper clip.
Then the intake for the engine comes from the air filter and goes to the front grommet on the valve cover.
The 4.0 engine does not tie in the charcoal canister to the CCV system, it uses a different canister all together that purges through a special fitting on the 4.0 air filter box.
Basically you have to use one system or the other, you cannot 'easily' mix and match them and expect the engine to run right.
I have heard of folks getting a PCV valve for the 4.0 cover and converting the cover over to the 4.2 system.
I think this is easier and cheaper than going the other way. Just the right canister for the 4.0 cover is $100.00 or more, where a couple grommets and chunks of hoses for a PCV are cheap.
I do know that folks have posted here about switching the CCV over to a PCV on a 4.0 valve cover, maybe ask that specific question.
What I'm not understanding is that in the article there is more parts going from the front gromet than what I have. Perhaps this is a difference between a stock 4.0L and the MPI kit.
I have only one line coming from the front gromet of the valve cover to the air breather assembly and attaches to a fitting. On the other side of that fitting is the tube that goes to the charcoal canister. The fitting is basically a T fitting.
I'll try to get a pic of what I have to show you but it's basically how I discribed.
I just had my 60,000 mile checkup in my '99 TJ Sport and they replaced both these parts as part of it. I looked into doing it myself first and at least the PCV part was cheap.
Bill and Mike, The kit comes as you descrbed it Bill. I have it on my CJ also. ALL original CJ 258 (4.2l for you metric types) smog/PCV etc kit gets trashed. The whole system is from the 4.0l system. Bill, your system isn't broken it's installed exactly as it's intended to be installed. It may need some cleaning/part replacement. Also as previously stated make sure there are no leaks in the system. It will upset the apple cart. Bill, if you need I can take pictures of my system and email them to you. Rich Harris
Mike's statement regarding my kit being broken (I bought it used) comes from a succession of things we've discussed in the past. This leads him to believe my kit is broken (gas wash or blow by issues). He believes my engine has/had gas wash caused by leaky injectors. Also that my Charcoal can could be bad (blowby).
I am thinking either the previous mechanic rebuilt the engine and didn't put it back correctly throwing off the O2 sensor causing a rich burning system. This causing the engine problems. (Only about 40k since the rebuild)
Or
The thing was never rebuilt as I was told and so it's just aged. (the machinest did say he felt a ring ridge on the cylinders)
I don't think I had the MPI kit on there long enough to do the kind of wear we're talking about.
However I've learned a lot from Mike and respect his input so just to be safe I am going to get the system checked out after the rebuild.
Thanks for the offer of pics. I'll let you know when I get to that part.
Checking it out would make 'me' feel better anyway Bill. ;-) I hate to see folks waste money...
The damage from gas wash can happen in a couple thousand miles. When gas gets into the oil, bad things happen fast. That one black plug was rich to the point of no fire and all the other strange things....
I have seen polished up engines like that before. Back in the days of carbs and stuck floats. The cylinders would get polished up soo sweet about the time she started knocking from lack of lube on the crank bearings....
Anyway, it is worth getting it right for sure after all this work and money in my mind.
That CCV system is so bitchy and causes blowby so fast....
These guys are going the other way..
They are taking the PCV's out of their 4.2 engines and putting a 4.0 top and cover on them with CCV's!!!!
I wasn't going to get into that with Bill, the original poster. He has enough issues just to get it running the way the kit calls for to worry about messing with it....
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