So after considerable testing and trial-and-error, we found the culprit(s) to the smoking problem on my '87 XJ6.

First off, the problem with losing power in some situations was traced to a faulty coolant temp sensor, which must have been confusing the fuel map constantly. We switched in a new sensor, and the problem was solved.

As for the smoking problem, we noticed it was only coming around when the car was warmed up and operating over 2,500 rpm. The problem would get worse the heavier the load you put on the motor (i.e., passing, going uphill, etc.).

Turns out the oil wasn't coming from the tailpipe at all, but from the exhaust under the hood: Oil was being spilled onto the hot metal and burning off.

Well, we've found where it's coming from: The oil cap itself, and the dipstick. The dipstick is getting physically pushed up out of its receiver, even now that the breather screen has been changed. Oil is seeping out from around the oil cap no matter how tight it's screwed on.

The dipstick is positioned right above the exhaust run, and oil is simply blowing out from under the dipstick and onto the hot exhaust. Oil is also running out from the bottle of the oil cap, running down the valve cover, then dripping off at the back. What's more, the dipstick seems to solidly stick into place when you put it in its receptacle.

Are these problems common, and if so, how to fix?

Jess

 

Which suggests the crankcase is being pressurized.

Since the breather is clean (did you clean the pipe at the same time?) I wonder if you're getting excessive blow-by past the piston rings.

If you remove the oil cap with the engine running does smoke come out?


The cap has a rubber seal which might need replacing....but that won't solve a blow-by issue.

Cheers
DD

 

!!!


Amongst my issues I found smoke at the left rear corner of my Lump's engine bay. Almost for sure a weeping OP sensor.


Fixes deferred along with it's smoke from exhaust issue til warmer and dryer weather predicted for next week.


Carl

 

I don't think we did the breather hose at the same time. I'll have to ask the shop but unless they took it on themselves, it didn't get done. There was no hose available from Jagbits, where I ordered the other parts.

I tested tonight, on a warm engine, to see if I could get it to smoke out of the oil cap if I took the cap off. It did not emit any smoke from that hole.

One thing I did solve tonight, though: My oil cap has no gasket on it. There is evidence that one used to be there, but it's not there anymore. I ordered a replacement (and a replacement dipstick gasket) from Jagbits.

With no smoke coming out of the oil cap hole, what comes next?

Jess

 

You may still have a crankcase pressure problem

Wait and see if the breather pipe is clean.

A new breather screen can't work if the breather pipe is clogged.

Cheers
DD

 

UPDATE:

I asked the shop whether they changed the breather pipe or hose; they did not change it, but said they inspected it and found no issues. However, we decided to go ahead and do something a little different: We fabricated and installed a modern PCV valve system, putting it in the pipe after gases leave the breather.

Problem solved. No more oil out of the dipstick.

I'm still getting a little oil seepage from around the oil cap, even with the oil cap gasket installed. How tight am I supposed to turn this cap? I don't want to flatten the gasket but it seems like I have to turn it really tight to get it not to leak.

Jess

 

My .02.


The engine does create 'blow by". The PCV "positive crankcase ventilation" is a good move. The engine will "eat" the oil fumes.


Carl