- Joined
- 26 January 2021
- Messages
- 1
Is it normal for oil pressure to be almost zero on the gauge at idle?
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Oil pressure at idle
- Thread starter outlawten5
- Start date
at idle in my '01 it sits at ~2 marks above 0 on the gauge.
True, 20PSI , 2 marks, warmed up at idle is normal.
At zero as in the gauge does not move off the lower peg? That is definitely not normal. Is the red low oil pressure light illuminated which would indicate very low oil pressure or does it go out? If the low oil pressure light goes out your first step should be to check the operation of the gauge as described in the Electrical section of the service manual.
This is a common issue on the early NSXs. On the 1991-93 NSX gauges and the 94+ gauges, idle oil pressure should show on the gauge. Once it is up to operating temp, the needle should be around the first mark.
Some early 1991 cars had a defective oil pressure gauge. Those cars have VINs that end from 00887 to 03162. In those cars, the gauge could be defective and must be replaced. For all other NSX years, the sending unit can fail, which causes the same symptom (gauge shows zero) but has a different cause. Replacing the sending unit will fix it. However, if your NSX is between 00887 and 03162, replacing the sending unit might not do anything, since the gauge itself could be bad. The replacement part for the gauge is 78150-SL0-003 and can still be ordered from Japan.
However, as Old Guy mention, you should check to make sure you actually have oil pressure. Remove the oil switch on the filter pedestal and connect an oil pressure gauge. Start the engine and make sure you see at least 10psi idle pressure on the gauge. A healthy NSX usually shows around 20 psi at idle.
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I bought my 1996 NSX in 2003. From the time I bought it, the gauge has been on 0. Sometimes it might hop up to the very first hash mark. Most of the time it just sits on 0. I have driven it every way there is- fast, slow, traffic, hiway, twistys. Is it the gauge? Is it the sending unit? I don't know. I have just accepted that that's the way it is. I would love to have it working, but I don't want to turn into a dog chasing its own tail and getting nowhere. And trying to find someone in St. Louis that you can trust is a true crap shoot.
It's the sender. The gauge was only defective in some of the 1991 cars. You can get a new sender from Acura or Honda Japan.
- Joined
- 13 February 2023
- Messages
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My car is from St. Louis. The previous owner had it serviced at Mungenast Acura.
I wouldn't go there with a gun to my head. I always took it to Acura Of Brookfield. I heard so much about John Vasos and his team. They were great! But now John is not there anymore and he is dealing with health issues. They fixed a ton of stuff on it but not the oil pressure gauge problem. So I just live with it.
The oil pressure sender should be a pretty worthwhile fix. I think it's only a $50 part?
Looking at it another way, you're going to have to replace it when it comes time to sell, or take a way bigger $ hit when potential buyers discount what they're willing to pay based on their uncertainty about the cause, or their uncertainty about whether it's been driven around with inadequate oil pressure. I'd change it now, and also benefit while you own it from the added security of a gauge vs. just relying on the idiot light.
Looking at it another way, you're going to have to replace it when it comes time to sell, or take a way bigger $ hit when potential buyers discount what they're willing to pay based on their uncertainty about the cause, or their uncertainty about whether it's been driven around with inadequate oil pressure. I'd change it now, and also benefit while you own it from the added security of a gauge vs. just relying on the idiot light.
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That sounds like the "Passage - Oil Pressure Sensor" part which will come up in searches for the senor if you don't use the part number. The actual sensor is around $350 - $400 US$ at the parts discounters. The oil pressure switch on the oil filter pedestal is around $30 - $40.
Looks like you're right (I need an icon for not-surprised
) - it's probably not the $23 "passage" that's the problem - it's only a 90 degree bend to attach the sensor.
PASSAGE, OIL PRESSURE SENSOR, 37241PR7A00, $23
SENSOR, OIL PRESSURE, 37245PR7A02, US$151 from Amayama
www.amayama.com
Checking the sensor and/or replacing it seems doable according to p 23-137 of the 97 service manual, available in the Prime library, especially if you're changing the oil anyway.
) - it's probably not the $23 "passage" that's the problem - it's only a 90 degree bend to attach the sensor.PASSAGE, OIL PRESSURE SENSOR, 37241PR7A00, $23
SENSOR, OIL PRESSURE, 37245PR7A02, US$151 from Amayama
Honda 37245-PR7-A02 (37245PR7A02) SENSOR, OIL PRESSURE
Honda 37245-PR7-A02 (37245PR7A02) SENSOR, OIL PRESSURE. New & genuine Japanese car parts. Fast shipping. Low prices. Request a quote from Amayama Trading Co. online.
www.amayama.com
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Yeah the culprit is the sender, not the pressure switch on the filter pedestal. All the pedestal switch does is light up the oil pressure idiot light in the dash if it drops below a certain pressure.Looks like you're right (I need an icon for not-surprised) - it's probably not the $30 passage that's the problem.
PASSAGE, OIL PRESSURE SENSOR, 37241PR7A00, $23
SENSOR, OIL PRESSURE, 37245PR7A02, US$151 from Amayama
Checking the sensor and/or replacing it seems pretty straightforward according to p 23-137 of the 97 service manual, available in the Prime library, especially if you're changing the oil anyway.Honda 37245-PR7-A02 (37245PR7A02) SENSOR, OIL PRESSURE
Honda 37245-PR7-A02 (37245PR7A02) SENSOR, OIL PRESSURE. New & genuine Japanese car parts. Fast shipping. Low prices. Request a quote from Amayama Trading Co. online.
Where is the engine oil pressure gauge sending unit and how hard is it to change? From the pic on 6-22, it appears to be on the opposite side to the oil filter, but exposed. Is it in practice?
What is the part # for the pedestal switch if the idiot light is not coming on before the engine starts? 37240-P13-013?
www.amayama.com
On a side note, if the V-tec is working, is that a guarantee that the oil pressure is fine since oil pressure activates it?
What is the part # for the pedestal switch if the idiot light is not coming on before the engine starts? 37240-P13-013?
Oil cooler / breather for Honda NSX 1 generation 09.1990 - 11.2001 - Honda Car and Auto Spare Parts - Genuine Online Car Parts Catalogue - Amayama
Oil cooler / breather for Honda NSX 1 generation 09.1990 - 11.2001. Buy OEM spare parts online. Low prices, proven reliability, fast shipping from Japan
www.amayama.com
On a side note, if the V-tec is working, is that a guarantee that the oil pressure is fine since oil pressure activates it?
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From my knuckle bashing coolant hose replacement exercise, my recollection is that it is on the front cylinder head on the left side (when looking forward) and is mounted just below the front spool valve assembly. That thing called the 'passage' is actually a right angle connector so that the sensor does not stick out directly from the side of the head. It was easy to see once you had a whole bunch of stuff removed for the hose replacement. With everything in place, there are some wire harness pieces blocking the view. Once the harnesses are disconnected and pulled up I 'think' you should have a reasonable view of the sensor; but, access is going to be tight. I expect it will be doable; but, awkward as hell.
That is the correct number for the oil pressure switch on the oil filter pedestal.
If you have not generated a VTEC error code (P1259 or P 1279) you can probably infer that the oil pressure is OK.
That is the correct number for the oil pressure switch on the oil filter pedestal.
If you have not generated a VTEC error code (P1259 or P 1279) you can probably infer that the oil pressure is OK.
The gauge sender unit is mounted on the left side of the engine on the front head. It sits below the VTEC spool valve and is comprised of two parts: (1) The mounting block that mates to the head and (2) the sender unit itself, which is wrapped in a black rubber sleeve.
It is rather difficult to reach. Most people detach the coolant bottle from the firewall and push it out of the way. That improves access. It's impossible to remove just the sender unit since you'll never get a wrench in there, so you remove the mounting block instead. Note that the O-ring should be replaced and is one of the big culprits for oils drips on the engine.
37240-P13-013 is the correct part number for the dash light switch. Make sure to use Hondabond when you replace it.
Interestingly, for such a critical part of the engine system, it's really hard to test the VTEC system. The ECU uses a pressure switch (the green plug on the spool valve), but it's more of a safety catch than a test. All the pressure switch does is look for adequate oil pressure at the spool valve when a VTEC command is initiated by the ECU. If it sees good pressure, it tells the ECU that it is safe to engage VTEC. If there is not enough pressure, VTEC won't activate. In this case, you would get a DTC code (22 or 52 on the 91-94) for the spool valve pressure switch, but it doesn't actually tell you anything other than there wasn't enough oil pressure to safely engage the high cam. It tells you nothing about the actual VTEC system in the sense that you have no idea of the rocker pins shifted and locked the lifters.
The only other test is to connect an oil pressure gauge to the 10mm VTEC test ports and follow the test on pages 6-18 to 19. This test checks the VTEC solenoid itself- there should only be oil pressure at the test port with the solenoid activated.
There really is no other way to check if the VTEC rocker pins engage. Another fun fact is that many of the later Honda VTEC engines got rid of the pressure switch since apparently the system is so reliable they felt it wasn't needed. As Gen 1 VTEC system, the NSX has this extra safety margin.
EDIT: There's actually one more VTEC test you can do. This is a physical test of the rocker arm locking mechanism. It's on pages 6-52 to 53. Basically, you apply shop air (> 37 psi) to the VTEC test port while plugging the relief hole in the head. You check each cylinder at TDC to see if the rocker arms are locked together when air pressure is applied. This test requires the valve covers to be removed, so you can't do it on a running engine.
It is rather difficult to reach. Most people detach the coolant bottle from the firewall and push it out of the way. That improves access. It's impossible to remove just the sender unit since you'll never get a wrench in there, so you remove the mounting block instead. Note that the O-ring should be replaced and is one of the big culprits for oils drips on the engine.
37240-P13-013 is the correct part number for the dash light switch. Make sure to use Hondabond when you replace it.
Interestingly, for such a critical part of the engine system, it's really hard to test the VTEC system. The ECU uses a pressure switch (the green plug on the spool valve), but it's more of a safety catch than a test. All the pressure switch does is look for adequate oil pressure at the spool valve when a VTEC command is initiated by the ECU. If it sees good pressure, it tells the ECU that it is safe to engage VTEC. If there is not enough pressure, VTEC won't activate. In this case, you would get a DTC code (22 or 52 on the 91-94) for the spool valve pressure switch, but it doesn't actually tell you anything other than there wasn't enough oil pressure to safely engage the high cam. It tells you nothing about the actual VTEC system in the sense that you have no idea of the rocker pins shifted and locked the lifters.
The only other test is to connect an oil pressure gauge to the 10mm VTEC test ports and follow the test on pages 6-18 to 19. This test checks the VTEC solenoid itself- there should only be oil pressure at the test port with the solenoid activated.
There really is no other way to check if the VTEC rocker pins engage. Another fun fact is that many of the later Honda VTEC engines got rid of the pressure switch since apparently the system is so reliable they felt it wasn't needed. As Gen 1 VTEC system, the NSX has this extra safety margin.
EDIT: There's actually one more VTEC test you can do. This is a physical test of the rocker arm locking mechanism. It's on pages 6-52 to 53. Basically, you apply shop air (> 37 psi) to the VTEC test port while plugging the relief hole in the head. You check each cylinder at TDC to see if the rocker arms are locked together when air pressure is applied. This test requires the valve covers to be removed, so you can't do it on a running engine.
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Yes, life will be slightly easier if you do this at the same time as you are doing a cooling hose replacement.
I know another VTEC test you can do, an auditory test while the engine is running. I test mine on a regular basis. 
Is this a TSB for vehicles within the range of the VIN? Curious where I can find information so I can see anything else this vehicle might be having issues with.
Additional data point:
My oil pressure gauge was malfunctioning until I sent the cluster to be repaired. My assumption is that aging capacitors in the cluster can also cause wonky readings.
To OP, if you haven't sent the cluster off to Brian K to be repaired, do so now. Failure of the cluster may cause a fire, and could also be the cause of your bad oil readings.
My oil pressure gauge was malfunctioning until I sent the cluster to be repaired. My assumption is that aging capacitors in the cluster can also cause wonky readings.
To OP, if you haven't sent the cluster off to Brian K to be repaired, do so now. Failure of the cluster may cause a fire, and could also be the cause of your bad oil readings.
There are very few TSBs for the first generation NSX and I don't recall the pressure gauge sensor being one. If you want to find a listing of the TSBs, use the internet archive / Way-back Machine to retrieve a stored copy of NSX Prime from about 4 - 5 years ago and in the NSX Prime library of the archived copy you will find a section listing all the TSBs
It's TSB 91-008, which provides the same information discussed in the earlier posts here. The oil gauge units for the 1991 cars between 00887 to 03162 were known to be defective. But, now that the NSX is 30+ years old, other causes are possible that were not in 1992, when the TSB was issued. As discussed, the gauge board capacitors can go bad and cause gauge issues. The sending unit also can be a problem. If it were me, I would have BrianK refurb the gauge cluster and buy a replacement gauge from Amayama.
Was already pricing the gauge. I will likely send the cluster out to Brian when im having the rack rebuilt and doing all the brake work.
Thanks as always for the response! You as well @Old Guy
There isn't much to go wrong with the gauge so I don't understand the reason for replacement. The background color of the gauge also changed slightly during a few model years too.
I think maybe just rotate the needle pointer on the gauge axle a few degrees.
I think maybe just rotate the needle pointer on the gauge axle a few degrees.
kg/cm2 =14.2 psi , 2marks is little over 28psi ,
