Foxbody Burning Oil

[Greeneyedfox]

I have a 91 mustang lx 5.0. Its burning oil but im unsure if its the valve seals or the rings. At start up itll shoot out a puff of smoke. Upon acceleration you can smell oil being burnt towards higher rpms. Also at idle you can very strongly smell oil being burnt but no visable smoke. It has no cats. Pcv has been replaced also.

 

[Adieu]

Time to run a compression check. It's not hard to do, and a basic compression tester is all of $50-60 at Harbor Freight or a parts store.

 

[Greeneyedfox]

Time to run a compression check. It's not hard to do, and a basic compression tester is all of $50-60 at Harbor Freight or a parts store.

Will a compression test tell me in what shape the oil control rings are tho?

 

[Adieu]

Will a compression test tell me in what shape the oil control rings are tho?

Yes.

If you run a compression check and any of the cylinders have low compression, the next step is to add a tablespoon or so of oil to that/those cylinder(s) and check again. If the number goes up, it's rings, if it stays the same, it's something else.

 

[Blandnuts]

I would check all pvc lines and make sure you're not sucking oil into the intake. If that's the case, a catch can could solve your problem.

Compression test does that, checks compression or the compression ring. Adding oil will help the compression ring seal.

A leak down test would help you find where you have a problem... rings, valves....

Typically, a puff of smoke on startup is valve seals, but could be oil being pulled in from the intake too.

No cats make a car smell like crap regardless of burning oil.

 

[Greeneyedfox]

Yes.

If you run a compression check and any of the cylinders have low compression, the next step is to add a tablespoon or so of oil to that/those cylinder(s) and check again. If the number goes up, it's rings, if it stays the same, it's something else.

Ill rent the compression tester and ill post the results.

 

[Greeneyedfox]

I would check all pvc lines and make sure you're not sucking oil into the intake. If that's the case, a catch can could solve your problem.

So just check the vacuum line running from pcv to intake for oil. And the pcvs are a pain to reach lol.

 

[Blandnuts]

Yes, the pvc line end and the one on the valve cover.

 

[Greeneyedfox]

Also i was reading around and sonewhere i read that when the motor is running and you take the oil cap off and it blows air out it means the rings are bad. Just for the hell of it i tried it and it sucks in air slightly. Also the hose running from the oil filler neck to the intake has some oil in it. I replaced the pcv, the screen and tge gromet but i just took a look at it and it isnt sitting all the way. It keeps popping nack out.

 

[89oem]

After market pcv and grommet are well known for fitment issues, did you get Motorcraft?

 

[Greeneyedfox]

After market pcv and grommet are well known for fitment issues, did you get Motorcraft?

Honestly i dont remember. And i cracked that hose from pcv to the underside of the intake and replaced it regular hose. Im sure the original is molded and thats why it wont stay pushed in because of the non molded hose wanting to twist it.

 

[89oem]

I believe its just vacuum hose, regular hose will collapse under vacuum

which may be pulling out the pcv

crack was probably because the hose had aged and turned hard...

 

[Greeneyedfox]

I took a look behind my intake where the pcv valve is and theres oil back there. Doesn't look fresh tho. But im going to Teflon wrap the outside of the grommet to get it to fit in tight until im able to get the better grommet and OEM pcv hose. Somebody was talking about a catch can. If i were to do that would i run a line from pcv on the back of the intake to the catch can then into the intake? And the line that connects the oil filler neck to the throttle body/intake would i need to run that to the catch can also considering theres oil in the line?

 

[Blandnuts]

Use Fuel line/PVC/EEC hose. Others will crack, harden, or collapse (eventually). Make sure the parts person gets you the right hose, most will grab normal vacuum hose.

The catch can really depends on if that's your issue (mods, supercharger/turbo....or excessive blowby). Also, where it's sucking the oil in. Typically, you run one on the pvc valve side.

pvc valve>hose>catchcan>hose>intake

If it's the other side you'd run one on that side.

oil fill tube>hose>catch can>throttle body

Don't connect pvc valve side to the valve cover side.

Not all catch cans are created equal. I would pass on being cheap and getting the air/water separators from Lowes or Homedepot. I personally like Bobs catch can. Again, this is irrelevant if this isn't your issue.

When I disconnected a line, oil would drip out when it had a problem sucking oil. This was with a China cobra intake.

What mods does this vehicle have? Miles?