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“Chugging” noise.


moozieman

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Nothing screws up the idle like a vacuum leak. As noted above, that filter on the valve cover opening is bad news, and a major vacuum leak.  It's a pain to trace and check the vacuum hoses on these engines, but they are often the problem.

Edited by Pilgrim
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On 6/20/2020 at 12:46 PM, Pilgrim said:

Nothing screws up the idle like a vacuum leak. As noted above, that filter on the valve cover opening is bad news, and a major vacuum leak.  It's a pain to trace and check the vacuum hoses on these engines, but they are often the problem.

I had mentioned this in a previous thread, the previous owner plugged up the breather port on the block with a freeze plug. Therefore I have no pcv valve. I added that filter up top to act as my vent

 

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1 minute ago, Zed Head said:

Did you do this test yet?  Below.  And check the vacuum line to the FPR for fuel.  It might have a blown diaphragm.

image.png

I’m confused. This test is for water temp sensor? (Which btw, my thermotime and water temp are unplugged) (it doesn’t run otherwise.)?

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Yes, if the water temperature sensor is disconnected the ECU will supply maximum extra fuel.  That's probably why yours is running so rich.

If it doesn't run when it's connected it might be because it is shorted out, making the mixture as lean as possible.  Or because you have a large vacuum leak, maybe through the PCV system.

People often mess around for weeks or months trying to avoid doing the tests.  But there's a reason that Nissan created a completely separate book, very detailed, with instructions, illustrated, covering all of the years from 1975 through 1980, and published it.

 

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7 minutes ago, Zed Head said:

Yes, if the water temperature sensor is disconnected the ECU will supply maximum extra fuel.  That's probably why yours is running so rich.

If it doesn't run when it's connected it might be because it is shorted out, making the mixture as lean as possible.  Or because you have a large vacuum leak, maybe through the PCV system.

People often mess around for weeks or months trying to avoid doing the tests.  But there's a reason that Nissan created a completely separate book, very detailed, with instructions, illustrated, covering all of the years from 1975 through 1980, and published it.

 

How should I test for a short? It’s usually unplugged because of how rough it runs when it’s plugged in.

Edited by moozieman
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You really should check the engine for vacuum leaks.  I found mine and it completely changed how the engine ran and only took 10 minutes to find/seal all the leaks.

Here's how you're going to do it:

- head to harbor freight and buy a hand "transfer" pump like this one: https://www.harborfreight.com/Multi-Use-Transfer-Pump-63144.html

- get a rag and plug your air intake (otherwise the smoke will leak out here)

- unplug your brake booster and plug the "out" side of the pump's hose in there

- grab a pack of cigarettes from 711, light one and put its end into the "in" side of the pump and start pumping.  After 2-3 cigarettes your engine should be full and you will see smoke start to sneak out.  Cap/fix those leaks.

NOTE: You must do this when your engine is cold and this is done with the engine off.

 

I'd also check and make sure you are getting spark to all cylinders.  Pull all the spark wires and stick a screwdriver (with a plastic or wood handle) into where the wire connects to the plug and then hold the metal of the screwdriver a centimeter or two above some body metal and crank the car.  If you have spark to that plug you will see it arc to the car.

The video sounds like the car possibly isnt running on all cylinders.

If that is indeed the problem, don't stop there - seal your vacuum leaks too via the above method.

Edited by chaseincats
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