Oil pressure low and bouncy at idle after warmup.
05-11-2015, 04:36 PM
#1
Oil pressure low and bouncy at idle after warmup. I'm slightly concerned. The pressure sits right above the quarter mark at Idle while at operating temps. It bounces around a bit but only within a 1/8th margin. On cold start it stays at 40 PSI but it also bounces allittle. While warm the car also has a mild stumble almost like it's trying to quit... Not quite that bad though. I'm hoping the pump isn't dieing.
05-11-2015, 11:15 PM
#2
On The Tree
iTrader: (1)
Join Date: Nov 2014
Location: Sacramento Ca.
Posts: 130
Likes: 0
Received 0 Likes
on
0 Posts
Is this a new condition?Did you have more pressure prior to this? You gotta be really careful when you start losing oil pressure. If that pump is going you don't want to drive it. You could do irreversible damage. Could also be the oil pressure sending unit, or a clogged up cheap oil filter like a fram. I don't know about it making it sputter though.
Last edited by celtsean; 05-11-2015 at 11:22 PM.
05-12-2015, 01:40 AM
#4
LS1Tech Administrator
iTrader: (3)
Join Date: Nov 2001
Location: Schiller Park, IL Member: #317
Posts: 32,033
Likes: 0
Received 1,483 Likes
on
1,067 Posts
I'd start by verifying the accuracy of the gauge, either with a test mechanical gauge or by just changing the OPSU.
It's also possible that the unstable/low idle might be leading to OP fluctuations and overall lower pressure readings at idle.
The needle "quiver/shake" seems to be somewhat common and sometimes is better/worse with different OPSUs. Most of mine have had a bit of quiver from time to time.
It's also possible that the unstable/low idle might be leading to OP fluctuations and overall lower pressure readings at idle.
The needle "quiver/shake" seems to be somewhat common and sometimes is better/worse with different OPSUs. Most of mine have had a bit of quiver from time to time.
05-12-2015, 05:32 PM
#7
Moderator
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,835 Likes
on
1,145 Posts
If the OPSU checks out OK against a mechanical gauge, the next likely culprit is the oil pump o-ring. It's a $6 part, but takes a TON of work to get to and about $100 in other gaskets, not to mention tools if you don't have them and a new crank bolt.
I read a post from someone putting a few ounces of TransX in his oil to get that o-ring to swell up, and he said it worked like a charm. I tried it, and I have to say, my engine did quiet down some, and my pressure stays near 40. it only stalls the inevitable, though. Eventually, I'll have to replace that o-ring.
I read a post from someone putting a few ounces of TransX in his oil to get that o-ring to swell up, and he said it worked like a charm. I tried it, and I have to say, my engine did quiet down some, and my pressure stays near 40. it only stalls the inevitable, though. Eventually, I'll have to replace that o-ring.
Trending Topics
05-15-2015, 07:43 PM
#8
Is this a new condition?Did you have more pressure prior to this? You gotta be really careful when you start losing oil pressure. If that pump is going you don't want to drive it. You could do irreversible damage. Could also be the oil pressure sending unit, or a clogged up cheap oil filter like a fram. I don't know about it making it sputter though.
Im using Mobil 1 Synthetic 10W30 High Mileage - I use 5W30 in the winter and 10W30 in the summer with a Mobil 1 Oil Filter
I'd start by verifying the accuracy of the gauge, either with a test mechanical gauge or by just changing the OPSU.
It's also possible that the unstable/low idle might be leading to OP fluctuations and overall lower pressure readings at idle.
The needle "quiver/shake" seems to be somewhat common and sometimes is better/worse with different OPSUs. Most of mine have had a bit of quiver from time to time.
It's also possible that the unstable/low idle might be leading to OP fluctuations and overall lower pressure readings at idle.
The needle "quiver/shake" seems to be somewhat common and sometimes is better/worse with different OPSUs. Most of mine have had a bit of quiver from time to time.
This is an A4
If the OPSU checks out OK against a mechanical gauge, the next likely culprit is the oil pump o-ring. It's a $6 part, but takes a TON of work to get to and about $100 in other gaskets, not to mention tools if you don't have them and a new crank bolt.
I read a post from someone putting a few ounces of TransX in his oil to get that o-ring to swell up, and he said it worked like a charm. I tried it, and I have to say, my engine did quiet down some, and my pressure stays near 40. it only stalls the inevitable, though. Eventually, I'll have to replace that o-ring.
I read a post from someone putting a few ounces of TransX in his oil to get that o-ring to swell up, and he said it worked like a charm. I tried it, and I have to say, my engine did quiet down some, and my pressure stays near 40. it only stalls the inevitable, though. Eventually, I'll have to replace that o-ring.
Last edited by Need4Camaro; 05-15-2015 at 08:02 PM.
05-17-2015, 02:48 PM
#9
When at the operating temperature pictured, does the idle pressure stay at that level all the time, regardless of whether you're sitting in traffic or just coming off the freeway after a steady drive?
My needle is jumpy as hell and if I sit in traffic consistently, barely rolling, my pressure will steadily drop from 36-38 down to 25 or lower. But then after a consistent drive of say 10 or more minutes, it will go back up to 36-38. I suspect this may be the case with you because it's not possible for the pressure to drop almost 20 lbs just from a cold start to reaching hot operating temp. You have to sit there for a while for the temp to reach higher and the oil to get thinner for the pressure to drop more.
I will say that's a good call. You don't want to commit all that time and labor just to risk having something else fail. But who knows, maybe it's the wiring that's having some kind of obstruction where even after the new build, you'll still have the same oil pressure readings. Definitely check and replace the easy-to-reach parts first (OPSU and wiring). If you're not familiar with using a mechanic gauge like I am, just go to any car shop and they should be able to do that for you at a negligible cost.
My needle is jumpy as hell and if I sit in traffic consistently, barely rolling, my pressure will steadily drop from 36-38 down to 25 or lower. But then after a consistent drive of say 10 or more minutes, it will go back up to 36-38. I suspect this may be the case with you because it's not possible for the pressure to drop almost 20 lbs just from a cold start to reaching hot operating temp. You have to sit there for a while for the temp to reach higher and the oil to get thinner for the pressure to drop more.
I will say that's a good call. You don't want to commit all that time and labor just to risk having something else fail. But who knows, maybe it's the wiring that's having some kind of obstruction where even after the new build, you'll still have the same oil pressure readings. Definitely check and replace the easy-to-reach parts first (OPSU and wiring). If you're not familiar with using a mechanic gauge like I am, just go to any car shop and they should be able to do that for you at a negligible cost.
05-18-2015, 12:47 PM
#12
On The Tree
iTrader: (1)
Join Date: Nov 2014
Location: Sacramento Ca.
Posts: 130
Likes: 0
Received 0 Likes
on
0 Posts
I wouldn't go any thicker than a 40 weight. That is too much. I would only run a thinner 40 like Mobil1 0w40. That is not even recommended but people have done it with good results. A 50 weight ? No way! 20 is way to thick for a cold start as well. With ls1 clearances , I think that is asking for engine damage. But who knows maybe I'm wrong. I just have never heard that before.
Last edited by celtsean; 05-18-2015 at 02:53 PM.
05-19-2015, 03:08 AM
#13
Banned
Join Date: Apr 2015
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
Sounds like the OPSU to me as well. One of my LS1 f body's oil pressure needle has been doing this "flickering" for the past 30k miles or so. And occasionally reads lower than it should. Not all the time though, and only after it gets up to operating temp. 187k really isn't that many miles either. These LS1's run very hard for a very long time, if taken care of and not hammered on constantly.
05-20-2015, 07:03 PM
#14
I fully agree with celtsean and Stangkillr.
It's one thing to actually need an oil that thick and another thing to simply try it out to see if the oil pressure reading changes on a gauge that's connected to a possibly faulty sending unit that hasn't been checked or replaced.
The LS1 engine was designed to run 30 viscosity oil at normal operating temperatures, where the flow of oil is adequate to circulate throughout the specific tolerances between engine components. Running a thicker oil without the necessary clearance will accelerate wear, especially if you've already got sludge accumulated.
It's one thing to actually need an oil that thick and another thing to simply try it out to see if the oil pressure reading changes on a gauge that's connected to a possibly faulty sending unit that hasn't been checked or replaced.
The LS1 engine was designed to run 30 viscosity oil at normal operating temperatures, where the flow of oil is adequate to circulate throughout the specific tolerances between engine components. Running a thicker oil without the necessary clearance will accelerate wear, especially if you've already got sludge accumulated.
05-22-2015, 10:34 PM
#15
My 427ci that went 173,000 miles and my current 390ci has never....ever....used anything but 20w50. My new 390ci...and yes it is new....see's 75-80psi on cold start.....and never, ever drops below 40-42psi no matter how hot it gets or at idle......
I like that......pressure is a good thing....
I think this whole 20w30 and 20w40 thing is ridiculous. 5 minutes after the engine is running the oil is already thinning out......so I start at a thicker oil. It has served me well and about 100 other people I know who use it their LSx engines......
I can't understand why people use thin oil to start with........
.
I like that......pressure is a good thing....
I think this whole 20w30 and 20w40 thing is ridiculous. 5 minutes after the engine is running the oil is already thinning out......so I start at a thicker oil. It has served me well and about 100 other people I know who use it their LSx engines......
I can't understand why people use thin oil to start with........
.
05-23-2015, 10:15 PM
#16
oil viscosity (pressure) is dependent on temperature. a hot motor running 250°F oil temp is going to have low oil pressure, and much lower if its an aito trans where the idle is 550-600 rpm. 800 rpm vs 600 rpm is a 33% difference in oil pump speed and what it can put out, that is significant and why you see low oi pressure at hot low idle, it is mostly normal to have 10-15 psi using a 5w30 oil on a high mileage worn engine. i dont think
you have anything to worry about based on that 1/4 mark which is 20 psi.
use 20w50 oil, it is fine and will give you best protection at hot idle in traffic. simply dont start engine and go to 4000+ rpm before it warms up. 40 and 50 weight oil is for protection and longevity, 5w30 is for fuel economy lovin liberals who lease cars and will vote for hillary.
you have anything to worry about based on that 1/4 mark which is 20 psi.
use 20w50 oil, it is fine and will give you best protection at hot idle in traffic. simply dont start engine and go to 4000+ rpm before it warms up. 40 and 50 weight oil is for protection and longevity, 5w30 is for fuel economy lovin liberals who lease cars and will vote for hillary.
10-27-2020, 11:52 PM
#18
My oil pressure guage had been bouncey at operating temperature idle and not moving very smoothly for a while now.
I replaced the oil pressure sending unit and it didn't help the situation.
So, I swapped out the oil pressure stepper motor from a spare cluster and now my oil pressure guage moves nice and smoothly and doesn't bounce at idle anymore.
I replaced the oil pressure sending unit and it didn't help the situation.
So, I swapped out the oil pressure stepper motor from a spare cluster and now my oil pressure guage moves nice and smoothly and doesn't bounce at idle anymore.
11-07-2020, 04:12 AM
#19
On The Tree
My oil pressure gauge does the exact same thing. It started these oil pressure readings after I had the engine rebuilt. On a cold start, I'm looking at about 60 psi according to the gauge. Once it's up to running temperature it idles right around the quarter mark but anytime you touch the gas it jumps to right around 40 psi and pretty much hangs out right there as long as your touching the gas.