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Join Date: May 1999
Location: Burlington, NC
Posts: 273
MPS

I have a stock '74 2.0L.

Well, I got the engine all finished after having the heads rebuilt and installed in the car. I got the car started and fine tuned (to the best of my ability). It is runninig better than it has in many years.

I have a question though. When doing all the fine tuning things, I was testing the MPS and found the resistance between pins 8 and 15 was not 350 ohms. Thinking that I had a busted MPS, I decided to take the blasted thing apart just out of curiosity. To my surprise, it had about an ounce of motor oil inside. I am guessing that it has been sucked in through the air distributor and that the source of this oil is the vacuum line coming from the PCV valve. Does any of this sound right to you?

Later, I remembered the post telling that the 8 and 10 pins are the two with a resistance of 350 ohms. I cleaned and reassembled the MPS, installed and adjusted it and it seems to be working fine without all that oil.

I am thinking of trying to rig some sort of filter in the vacuum line from the PCV valve to prevent this from happening again. Good idea or bad idea? I would like to hear some opinions on this.

Thanks

Pritchard

[This message has been edited by Pritchard (edited 12-06-1999).]
Old 12-06-1999, 05:59 AM
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On a 2.0L the MPS hooks up to the air intake by way of a vertically (pointing up) mounted vac port near the TB. The MPS has no vaccuum of its own, I can't see how the oil was sucked into it.

Only thing I can think of, WAG, is that you either had the MPS hooked up lower in the air intake and the NPS was mounted low in the engine bay. Some how oil came into the MPS vac line and dripped into the MPS. Either that or at an oil change someone spilled oil into the two slits in the MPS.

Which side of the diaphram was the oil on? The side with the slits (to measure the barometric pressure) also has the adjustment screw. The other (sealed) side has the "two flying sausers making love" type of thing.
Old 12-06-1999, 05:26 PM
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Hey! Nice Rack! "Celette"
 
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Wow, that discription is conjuring up visions from my disfuntional childhood. e.t. phone home.LOL
Old 12-06-1999, 10:18 PM
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Sounds like JP has it about right. I'll bet the hoses are not quite right,check the hose diagram at: http://www.pelicanparts.com/914/technical_specs/914_20FI_diag.htm
Note the line to the MPC has the vertical connector all by it self on the intake plenum. The PVC line goes to that double plastic fitting at the side of the plenum. It is very possible to get pressue in the PVC line at hi revs and that could have forced the oil into the MPC.
Old 12-07-1999, 07:20 AM
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Thanks for the ideas. I have the hose connected correctly, thanks to DD's diagram. That doesn't mean that I had them correct several years ago, however. I hadn't really thought that the MPS doesn't "suck" air into the sensor. So my theory is wrong. Anyway, I'm going to try and fashion a filter out of an old lawnmower air filter and place it in the oil filler contraption (sp?) to cover the intake to the PCV valve. Haven't actually eyeballed the inside of the contraption in a while so I'm not positive that this can be done. I might not even try to correct this problem at all.

Pritchard
'74 914 2.0L
Old 12-07-1999, 10:13 AM
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You might want to be very careful with the PCV valve as it is plastic and I don't think they are available anymore??? There is a ring on the inside of the vent box that holds it on and it is easily unscrewed with needle nose pliers. I clean ours with electronics cleaner so the plastic won't get damaged and someday I'll have to make a replacement from moderm materials. Does your car ever backfire? If so that means pressure is getting into the plenum and that could be getting the oil into the MPC.
Old 12-07-1999, 11:28 AM
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Thanks John. My original PCV valve is long gone. I broke it several years ago and have made do with another PCV valve. Yes my car has backfired a few times. Hopefully not too many more after much TLC.

Thanks

Pritchard
Old 12-07-1999, 11:58 AM
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