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Coupes & Convertibles Mazda Miata Mazda MX-5 Miata (2005 and earlier)
4340 messages, Last post on Aug 25, 2009 at 9:51 AM
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Can anyone out there help me out? I just bought a 1995 Miata so I'm new to the community (though I'm happy to finally own a car that's fun to drive). My oil pressure seems low when the car idles, and gets lower as the RPMs increase. I did some initial research and learned that the fuel pressure sensors Mazda used had a tendency to act up, so I assumed this was the problem, as there were no other indications of low oil pressure (no valve noise, knocking, banging, or overheating). However, I later discovered that after driving on the highway at speeds exceeding 3,000 RPM, there was considerable valve train noise upon slowing down and an increased operating temperature, all indicating that oil is not getting to the valve train. Further research indicated that this condition could be caused by either an improper grade of oil or a partially blocked oil pump screen. I cahnged the oil, which was obviously not the proper grade because the hot stuff I drained was thicker than the cold 5W-30 I replaced it with. However, this didn't fix the pressure reading. I've driven the vehicle around town, careful to keep it to under 3000 RPM, which seems to be the magic number, and the engine runs srong, sounds good, respondes well, and gives absolutely no indications that there is an oil flow problem. Tomorrow I will taike it on the highway and run it above 3,000 and see if I there is any noise. I think the problem was a combination of imporoper grade of oil and a faulty pressure gauge. I know this seems unlikley, but when I drove the car today, the gauge indicated no pressure, yet the vehicel performed fine (I was very careful). Once the car warmned up, I got the same readings (low idle, lower operational). I seems plausible that oil which is too thick (say 10W-50) would not work well at the high RPM the Miata was designed to sustain. Simultanoeusly, it also seems plausible that a faulty gauge would give bad pressure readings regardless of the oil used. The only other option I can think of is a clogged screen at the oil pump intake, which I will check if I get valve noise after running at 3,000+ RPMs. What I want to know is if there is anyone who can think of something I've missed, another cause for this that I should also check into. Obviusly, if the oil pressure drops when the RPMs increase, the problem is at the oil pump feed side. However, I've pretty much been a 6 - 8 cylinder guy prior to this, so any additional thoughts, advice, or information is greatly appreciated. Thanks and I look forward to more discussions. Daedalus1
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Replying to: daedalus1 (Aug 29, 2007 2:58 pm) I have a 1993 model, one of the last years that actually had the true, working gauge. I'm not sure if 93 or 94 was the last year, but I'm pretty sure it was a dummy gauge by the 1995 model. So don't trust the gauge. Surely the wrong oil was being used. You might want to use an engine cleaner treatment to flush it out, then drain and fill with thinner oil, or synthetic perhaps. |
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Replying to: daedalus1 (Aug 29, 2007 2:58 pm) |
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Replying to: vjdmx5 (Feb 19, 2000 4:28 pm)
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Replying to: dilger (Sep 11, 2007 6:27 pm) |
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my miata idles ok and after 2000rpms it has power but real slow take of speed and no power at all under a load ,going up a hill ect...we have replaced fuel filter,plugs,wires,airflow meter,both temp sensors still no power on the low end, im stumped any suggestions on what that might be? almost like you step to floor on the gas and once it gets past 2000rpm its fine but under that forget it....
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Replying to: dean21 (Sep 28, 2007 9:56 am) |
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I have a 1990 miata with 194,000 miles. I am certain that the crankshaft is bad (the key broke off but has been fixed). The car showed signes of a bad map sensor, so i replaced it. that did not help. i just recently bipassed the fuel pump relay and the car will idle great. Occasionally, it wants to die and will rev to 2000 rpm very slowly, then rev just fine. other times, it will rev from idle with no hesitation. my machanic and i are out of ideas. what could be causing this issue? i am not sure what all has been replaced, or it the car has proper timing. i was thinking a fuel filter is clogged or injector. anyone have any ideas?
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Replying to: cellis06 (Nov 20, 2007 12:41 pm)
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