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Oil pressure drops while revving up motor by pontiacfierokid1985
Started on: 10-08-2019 09:03 AM
Replies: 13 (243 views)
Last post by: David Riedle on 10-12-2019 11:43 AM
pontiacfierokid1985
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Report this Post10-08-2019 09:03 AM Click Here to See the Profile for pontiacfierokid1985Click Here to visit pontiacfierokid1985's HomePageClick Here to Email pontiacfierokid1985Send a Private Message to pontiacfierokid1985Edit/Delete MessageReply w/QuoteDirect Link to This Post

2.8 with140,000 miles. Is it weird for the oil gauge to do this I’ll be driving around 5 miles to 40 mph keeping shifts under 3000 rpm but once in 4th around 40 mph 2500 rpm oil pressure will stay right at above the red should I be worried. If I’m doing highway driving 65-70 mph 3500-4000 rpm 4 speed Muncie it will be close to 40 psi what should I check into first

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olejoedad
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Report this Post10-08-2019 09:54 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post

Check oil level.
How old is oil?
Put a known good mechanical gage on it to check.

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Blacktree
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Report this Post10-08-2019 11:19 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post

Chances are the main & rod bearings are starting to get a little loose. You could try a slightly higher oil viscosity, and see if that helps. BTW, what oil viscosity are you using now?

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Will
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Report this Post10-08-2019 11:53 AM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post

You said Muncie, so I guess this is an '85 or '86 car.

The 2.8's received some oiling system improvements for '88; the older engines wear out faster.

You could have worn bearings or you could have a bad sending unit. I'd find a way to use a mechanical gauge (it is difficult) in order to check the sending unit. You could also just replace the sending unit and see if the problem goes away.

If you verify that the problem is real, you can install a high volume oil pump while keeping your original regulator spring.

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pontiacfierokid1985
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Report this Post10-08-2019 02:59 PM Click Here to See the Profile for pontiacfierokid1985Click Here to visit pontiacfierokid1985's HomePageClick Here to Email pontiacfierokid1985Send a Private Message to pontiacfierokid1985Edit/Delete MessageReply w/QuoteDirect Link to This Post

I just added a quart yesterday so it’s on the full mark. I changed the oil out when I first bought it 136,000 miles on odometer. I’m going to change the oil and filter this weekend. it’s been 3000 miles already so it’s needing to be done also going to add some Lucas oil stabilizer to it as well since that helps with thickening it. I’m looking into getting a 3800 sc series 3 with a 4t65 out of a 2004-2005 Gtp over the winter. I want to keep the 2.8 going as long as possible til the 3800 is done and ready to go on the 86 fiero cradle with the 4 speed that is in the car now love my stick shift cars will never go back to auto in my older cars.

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olejoedad
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Report this Post10-08-2019 03:57 PM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post

The Fiero owners manual calls out 8000 mile oil changes.
The additive packages in modern oils dont even kick in till 3000 miles.

In your case, if the oil is clean on the dipstick, change the filter and top of with Lucas.

You're wasting money and resources changing oil at 3000 miles unless the engine exhibits a lot of compression blow-by.

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theogre
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Report this Post10-08-2019 04:34 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post

Yup... Even in the '80's, 3000 mile oil change is a myth/scam push by Jiffy Lube and others.

Adding any aftermarket crap to engine oils makes a lot of issues like Two additive packs can fight each other or add too much zinc etc that can poison the cat etc over time.

Heavy oil just hinds a problem and often makes more problems like using 10w to 20w anything won't flow in winter in a lot of places. So if you have wear problem now you often only get worse or car won't start in cold weather because heavy oil is grease.

Dash Gauges often have problems. Yes, check w/ a real gauge on OP port. 6V w/ AC is very easy but w/o AC have to go under the car.
Drop outs at higher RPM can engine/trans mounts bad and pulling on wires etc. Check mounts and dog bone(s).

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Blacktree
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Report this Post10-08-2019 04:43 PM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post

I agree with the above. The 3000 mile oil change interval is marketing hype. The owner's manual is a more reliable source of information.

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82-T/A [At Work]
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Report this Post10-09-2019 03:48 AM Click Here to See the Profile for 82-T/A [At Work]Send a Private Message to 82-T/A [At Work]Edit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by pontiacfierokid1985:

2.8 with140,000 miles. Is it weird for the oil gauge to do this I’ll be driving around 5 miles to 40 mph keeping shifts under 3000 rpm but once in 4th around 40 mph 2500 rpm oil pressure will stay right at above the red should I be worried. If I’m doing highway driving 65-70 mph 3500-4000 rpm 4 speed Muncie it will be close to 40 psi what should I check into first


Concurring with the other responses. Many years ago when my 87 was my daily driver, I had a similar issue. Turned out my oil pressure sending unit was going bad. It's located right off the front of the motor, which is facing the passenger side. It's that little cylindrical device that screws onto a tube that sits towards the front of the car off the engine. They're not expensive... but you can also test with a mechanical gauge.

If it's not that, 140k miles on an 80s car can be brutal if the oil hadn't been changed regularly. Not disagreeing with the guys above me, but our cars were generally run hard. Typically oil would get dirty and contaminated, and the engine would burn away some of the oil (blow-by) and be allowed to run low... further quickening the degrading of the oil that was left in there... so it was not uncommon for these motors to wear around that kind of mileage. With any car, good oil and checking the oil regularly would keep them running much longer.

If you are experiencing main bearing failure... (as in, the gauge is right), might be worthwhile to start succession planning. Either a new crate motor, or a bottom-end rebuild. I've seen people change out main bearings in a parking lot... don't recommend that, but it'll get the job done... hahah.

Another option is a windage tray and a new oil high-volume oil pump to make up for the loss of pressure from the enlarged clearances.
 
quote
Originally posted by Will:

The 2.8's received some oiling system improvements for '88; the older engines wear out faster.



Do you happen to know what these changes are? I've owned 9 Fieros, but not a one of them have been 88s. I know the oil pump is different, but curious if there's anything else specifically. I don't assume there's anything I can simply take from the 88 and install in my own 87 motor?


Thanks!

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Dennis LaGrua
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Report this Post10-10-2019 02:45 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post

On cars where there was low oil pressure, we found one where the oil pump was pumping lower pressure, another where the oil pressure sender was defective and one where the engine was just high mileage worn. Its most likely one of these issues.

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Report this Post10-11-2019 04:26 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by 82-T/A [At Work]:
Another option is a windage tray and a new oil high-volume oil pump to make up for the loss of pressure from the enlarged clearances.
Often that doesn't help.
Factory oil passages have many issues and adding High Volume/Pressure pumps often doesn't = to crank and other bearings getting more oil. Often only show on gauges making a bogus case for rest of engine will get more oil. Worse many HV pumps can "Peg" the regulator open because of OE oil plumbing and see high pressure that can "peg" the OE gauge and cause problems w/ many brand of filters.

Lets say you have a filter case that handles high volume/pressure w/o problems... Filter Media can have problems of it's own and if media fails and plugs up then you hope Filter Bypass in many GM engine not just Fiero dukes and V6 flows enough oil to save the motor. Even w/ that then engine is functionally running w/o a filter and that can plug up many things and often fast too.

Every engine that uses PF47 52 and related have no bypass in them. Is In the Engine w/ most are in the Filter Mount area. Many use ACDelco PN 25014006 including many Current Gas and Diesel engines. Currently 2265 Total number of applications. https://parts-catalog.acdel...=5561&parttype=10662
(Newer bypasses may have a very small "filter" but isn't like using the main filter for several reasons.)

Heavy oils can have same problem and bypassing the filter. Worse when weather is cold because Media can't flow oil turn to grease.

[This message has been edited by theogre (edited 10-11-2019).]

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Will
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Report this Post10-11-2019 04:00 PM Click Here to See the Profile for WillClick Here to Email WillSend a Private Message to WillEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by 82-T/A [At Work]:
Another option is a windage tray and a new oil high-volume oil pump to make up for the loss of pressure from the enlarged clearances.


 
quote
Originally posted by theogre:Often that doesn't help.
Factory oil passages have many issues and adding High Volume/Pressure pumps often doesn't = to crank and other bearings getting more oil. Often only show on gauges making a bogus case for rest of engine will get more oil. Worse many HV pumps can "Peg" the regulator open because of OE oil plumbing and see high pressure that can "peg" the OE gauge and cause problems w/ many brand of filters.

Lets say you have a filter case that handles high volume/pressure w/o problems... Filter Media can have problems of it's own and if media fails and plugs up then you hope Filter Bypass in many GM engine not just Fiero dukes and V6 flows enough oil to save the motor. Even w/ that then engine is functionally running w/o a filter and that can plug up many things and often fast too.

Every engine that uses PF47 52 and related have no bypass in them. Is In the Engine w/ most are in the Filter Mount area. Many use ACDelco PN 25014006 including many Current Gas and Diesel engines. Currently 2265 Total number of applications. https://parts-catalog.acdel...=5561&parttype=10662
(Newer bypasses may have a very small "filter" but isn't like using the main filter for several reasons.)

Heavy oils can have same problem and bypassing the filter. Worse when weather is cold because Media can't flow oil turn to grease.



On two occasions I've used a high volume pump with the original regulator spring to help engines which were worn enough to light the low oil pressure light during heat soaked idle in traffic. On both units, the extra volume kept the oil pressure at heat soaked idle high enough to prevent the low oil pressure light from lighting. Both went on to drive many thousands more miles.

[This message has been edited by Will (edited 10-11-2019).]

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82-T/A [At Work]
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Report this Post10-12-2019 02:58 AM Click Here to See the Profile for 82-T/A [At Work]Send a Private Message to 82-T/A [At Work]Edit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by theogre:

Often that doesn't help.
Factory oil passages have many issues and adding High Volume/Pressure pumps often doesn't = to crank and other bearings getting more oil. Often only show on gauges making a bogus case for rest of engine will get more oil. Worse many HV pumps can "Peg" the regulator open because of OE oil plumbing and see high pressure that can "peg" the OE gauge and cause problems w/ many brand of filters.

Lets say you have a filter case that handles high volume/pressure w/o problems... Filter Media can have problems of it's own and if media fails and plugs up then you hope Filter Bypass in many GM engine not just Fiero dukes and V6 flows enough oil to save the motor. Even w/ that then engine is functionally running w/o a filter and that can plug up many things and often fast too.

Every engine that uses PF47 52 and related have no bypass in them. Is In the Engine w/ most are in the Filter Mount area. Many use ACDelco PN 25014006 including many Current Gas and Diesel engines. Currently 2265 Total number of applications. https://parts-catalog.acdel...=5561&parttype=10662
(Newer bypasses may have a very small "filter" but isn't like using the main filter for several reasons.)

Heavy oils can have same problem and bypassing the filter. Worse when weather is cold because Media can't flow oil turn to grease.



I agree with you Ogre... I see it more though as a temporary fix until such point that the owner does a full engine rebuild. It's kind of like a bottle of Bar's Engine Fix... which I've never used, so we're clear! Hah...

The increased oil pressure is enough at least to get oil to where it needs to go to keep oil pressure in the lifters so the car doesn't get valve rattle. Basically... to keep the car running ~10k more miles where it would probably have died before then.

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David Riedle
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Report this Post10-12-2019 11:43 AM Click Here to See the Profile for David RiedleSend a Private Message to David RiedleEdit/Delete MessageReply w/QuoteDirect Link to This Post

I have used Amzoil Engine and Transmission Flush (FLSHCN-EA) with great success. You pour it in, idle for 10 minutes, and flush it.

Personally, I would then run Royal Purple Duralec 15W40 motor oil for 2,000 miles. I would then drain it, and put in whatever motor oil you normally use.

Synthetic motor oil is one of the best ways to clean an engine oil out. The RP Duralec oil is a professional-grade diesel motor oil that has a higher detergent concentration than regular synthetics, and since it is a 15W40 oil, it has a higher viscosity, which should help with the oil pressure. The synthetic oil will give you more protection than Dino oil, so it should not contribute to the problems...

If, after changing it, and use a known-good mechanical gauge, the problem still exists, you have mechanical issues.

This is my two-cents worth of advise, (which is probably not worth two-cents...)

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