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Old 01-04-2017, 07:09 PM   #1
///digitalme's Avatar
Join Date: Dec 2009
Location: santa ana ca
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Gas mixing with oil

Ive been tackling this for a few weeks now gas is somehow getting into the oil. I have gone through two sets of mepeh injectors, i changed the fpr, i have new temp sensors, new radiator, new wires, new plugs. New intake gaskets., Somehow the oil and gas are still mixing. I put the stock injectors back and still mixing. Im out of ideas of what to check, i dont want to dump money on new injectors and not being the problem. Anything else i have missed? Or suggestions?

Ps. I dont have any sort of smoke or loss of power, just rough idle when the car gets warn. I didnt have the problem until i changed the injectors to the rebuilt ones, and when i changed the temp sensors

Last edited by ///digitalme; 01-04-2017 at 07:21 PM.
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Old 01-05-2017, 06:56 PM   #2
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Location: Port Republic, MD
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As I'm sure you know, oil/fuel mix in only two ways, past rings or past stem seals.

So, you can leakdown check the engine, try to ascertain that the injectors are flowing normally, or check fuel pressure.

There is a possibility that the cam sensor is damaged, although that should throw a code, and if it were it would be batch firing injectors, increasing the possibility of fuel getting past the rings. So, I'd do a quick resistance check.

Any chance that you swapped connectors on the temp sensors?
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Old 01-05-2017, 06:58 PM   #3
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I also vote for leakdown test.
1991 325iS turbo

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Old 01-05-2017, 07:16 PM   #4
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For sure do a leak down.

Quick home test, only valid on the m42...

Take your fuel rail out, but leave the injector clips and fuel lines attached so you can see the pintles. Turn the key to the "on" position. This will energize the fuel pump and build pressure. Note any dripping injectors. If you turn the key off, then back on, the pump "shouldn't" prime again for a few moments unless you disconnect the battery for at least another minute or so.

If it passes that test, next pull the fuel pressure regulator vacuum line off and take a whiff. If it smells like fuel, the diaphragm may be torn and when letting off the throttle vacuum in the manifold may be pulling fuel back. If you have a vacuum pump of any sort (hand pump works great), you can apply vacuum to the FPR hose and it should hold for a very long time.
-john "If you can't afford to do it proper the first time, what makes you think you can afford to do it again?"


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Old 01-06-2017, 03:44 PM   #5
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did you mix up the coolant temp sensor plugs?
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