Engine Oil indicator fluctuating [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Engine Oil indicator fluctuating


wdmalik
09-25-2010, 08:15 AM
Main engine oil indicator in my GMC Envoy 2002 fluctuates and I get "stop engine" in DIC. Last time there was an oil leak as the technician did not tighten the drain plug properly during oil change, but now I have check and there is no oil leak, also oil level is full. Still I am getting the fluctuations,
Any suspected reasons, sensor faulty ?, dirt inside ????

Super 88
09-25-2010, 08:27 PM
Main engine oil indicator in my GMC Envoy 2002 fluctuates and I get "stop engine" in DIC. Last time there was an oil leak as the technician did not tighten the drain plug properly during oil change, but now I have check and there is no oil leak, also oil level is full. Still I am getting the fluctuations,
Any suspected reasons, sensor faulty ?, dirt inside ????
Most likely a faulty sensor, but do you have any unusual noises?

wdmalik
09-26-2010, 05:15 AM
No sound, nothing ..

can anyone tell me where is this sensor located ?

any part # please.

Thanks

wdmalik
09-26-2010, 08:23 AM
Also I found one more thing, when the vehicle is idle oil pressure indicator fluctuates and i get "Oil pressure low, stop engine" indication.

When in running, (RPM above 1000) things seem to be OK ... any insight please ?

RayVoy
09-26-2010, 08:11 PM
that almost sounds like a faulty oil pump.It could be, but I'd try super 88's suggestion first and change the sensor.

It's mounted just above the oil filter

wdmalik
10-05-2010, 12:00 PM
OK, I changed the sensor but no use .. so I took the vehicle to GMC Dealer. He diagnosed the problem to gauge (some issues with the gauge magnet)

Repair options given by him are not accepted as I have to give him vehicle for 4 weeks. Anyone with a solution how to repair the gauge.

the roadie
10-05-2010, 12:55 PM
Bad stepper motor in the instrument cluster, then. There's an article about changing them. In the US, you can buy the steppers for $5 or so plus shipping if you can solder them in vourself.

Make sure the oil indication is truly faulty, though. My experience is that a faulty gauge will not set off the "oil pressure low" indicator. If you have a dirty throttle body (how many miles do you have, and has it EVERY been cleaned), and your idle is fluctuating down to 300-400 RPM instead of the commanded 600, then the oil indicator is right, and you need to solve the erratic idle problem.

Is your idle steady? If not, does it get better with the AC turned off?

wdmalik
10-05-2010, 03:27 PM
Here are the snaps of DIC at IDLE, 1500 RPM & 2000 RPM

http://img831.imageshack.us/img831/4402/imag0230q.jpg (http://img831.imageshack.us/i/imag0230q.jpg/)


http://img693.imageshack.us/img693/3656/imag0233x.jpg (http://img693.imageshack.us/i/imag0233x.jpg/)

http://img522.imageshack.us/img522/7286/imag0234m.jpg (http://img522.imageshack.us/i/imag0234m.jpg/)

As IDLE seems to be OK, some other suggestions ?????

the roadie
10-05-2010, 04:37 PM
That looks entirely normal to me. When you say "fluctuates", I think you mean "varies up and down irregularly and randomly".

If you mean the gauge just goes up a little bit as RPM increases, that's normal. The PCM is creating a ficticious number to make the driver feel as if they have a real sensor, even when the I6 engine does not.

If you have a steady idle at 600 RPM, and it doesn't vary, and the gauge intermittently goes to zero, that usually means a failing oil pump if it isn't the pressure switch.

Is your idle RPM steady?

wdmalik
10-06-2010, 12:15 AM
When I say fluctuate, I mean it goes to 'zero', I get error message "Oil Pressure Low Stop Engine" which normalizes with 10 secs or so. Sometimes it never happens for days and sometimes it is continuously coming.

Just latest example, my truck was parked at GMC workshop for 4 days. According to the tech there, he took it for road test 5 times for 30 mins each and never found a thing. He suggested faulty gauge keeping the fact in view that the gauge goes to its normal position very slowly (others will go immediately to their positions as soon as ignition is turned ON). I took the truck home (5 KMs from workshop) and then I went to supermarket (1 Km from my home) and I started to get fluctuating errors.

TECH was telling me that it is only with ENVOY that you don't get a separate gauge. Still I am unable to find someone in local market who can repair the gauge for me :sadcry:

the roadie
10-06-2010, 12:37 AM
Last time I'll ask: Is your idle RPM steady? When your oil pressure goes to zero is it with a steady RPM or does the RPM go down at the same time as the oil pressure? Does it change with the AC off?

wdmalik
10-06-2010, 12:47 AM
Sorry, I was supposed to answer that in my last post.

IDLE RPM is steady, no fluctuations. Gauge goes to zero with steady RPM. I always get the fluctuations when engine shifts to IDLE (never happens in normal running mode).

IDLE RPM doesn't increase with A/C off, honestly don't know about the gauge behavior. Will check and revert.

Thanks

wdmalik
10-06-2010, 07:10 AM
I have checked without A/C & with A/C.

First I ran the truck on IDLE without A/C for 15 mins, at the start RPM started 1200 RPM and slowly came down to 700 RPM within 1 minutes. No indication came for these 15 minutes.

After I turned on A/C for 15 minutes (it was still on IDLE). RPM were around 700, no indication came this time as well.

wdmalik
10-06-2010, 08:29 AM
Here is what I am going to do before I finally decide to change the stepper motor


Cleaning of Throttle Body (Also This (http://forums.trailvoy.com/showpost.php?p=1002412&postcount=1))
Replacement of Engine Oil, my intention here to get the system completely flushed before the oil is replaced


Any other suggestions are welcome,

berto1014
10-06-2010, 09:42 AM
Seafoam your crankcase with the new or old oil. This has potential to fix the issue if its not the pump. I've had that happen before where it says low oil pressure turn off engine. I wanted to pull over since I was in the middle of an intersection but GM programmed the vehicle to completely ignore my throttle position when that code pops.

wdmalik
10-08-2010, 08:00 AM
Make sure the oil indication is truly faulty, though. My experience is that a faulty gauge will not set off the "oil pressure low" indicator. If you have a dirty throttle body (how many miles do you have, and has it EVERY been cleaned), and your idle is fluctuating down to 300-400 RPM instead of the commanded 600, then the oil indicator is right, and you need to solve the erratic idle problem.

Is your idle steady? If not, does it get better with the AC turned off?

Can you please specify what i need to do in addition to throttle body cleaning and oil change to make sure that my idle rpm is OK,

Thanks

Squeezmo
10-09-2010, 08:20 PM
A leak sensor, clogged sensor line, or a bad electrical connection (the plug is not waterproofed and gets soaked in oil). I watched this defect make my pressure drop off at 600 rpm when hot.

Fix: Clean and reseal the sensor and plug.

wdmalik
10-10-2010, 12:20 AM
Here is my latest finding which has made my troubleshooting even more complex.
When my truck has covered significant distance (55 miles in this case), oil pressure low indication came frequently on idle but this time engine temperature went above 100C (it is normally around 98C). Temperature gauge shifted back to normal when revs go up.

For the last week I drove in the city only (just from home to market which is hardly 1 mile and vice versa and from home to my office which is hardly 10 miles and vice versa) so I didn't feel any abnormality.

If the pump is really faulty, why things are OK at high revs and not OK at IDLE. I tested the idle rpm for 15 minutes and these were stable at 600 rpm.

Squeezmo
10-11-2010, 12:39 AM
The gage needles are positioned by the PCM. There is no oil pressure sensor... only a 16-18psi LOP_switch.

THis actually p*sses me off. That a maker of a vehicle would install gauges that lie to the operator about the condition of the machine is grounds for me not to buy any more GMs.

...that and the unCOnstitutional Government/Union takeover of the company... same with Chrylser...

Until the government and labor unions are slapped down for this, I am buying from non-Union American Car Manufacturers (Toyota, Mazda, BMW) from now on thank you very much!

wdmalik
10-12-2010, 12:21 AM
Here is final summary of my diagnosis for the last two weeks


I handed over the truck to GMC, they were unable to diagnose and 'suggested' that problem might be with gauge

Indication is coming on 'idle' only, i have tested rpm at idle with A/C & without A/C and these are stable.

I have changed the sensor with new, problem still the same.

I don't get any sound whatsoever from the engine, i read in the forums that rattling sound should come if oil pump fails.

I just found out that 'at idle', engine temperature starts rising and when it passes 100C, oil pressure gauge starts fluctuating. when i pump in gas, revs go up .. temperature stops rising up and i don't get any indication. I did a road test of the truck for more than 2 hrs without going to idle and both temperature and oil level gauge were stable (temperature gauge was max at 02 points before 100 indicator). I pulled over to a parking lot and with in 5 minutes the temperature reached 100 and oil pressure low indication started to come.


Now, I have a couple of questions,


If oil pump is faulty, why i get the indication on idle and everything goes smooth on high revs

If only gauge is faulty, why the indication is relating to temperature

Does leak in differential has anything relation with oil level indicator issue

Thanks

SparkyJJO
10-12-2010, 12:25 AM
Here is final summary of my diagnosis for the last two weeks


I handed over the truck to GMC, they were unable to diagnose and 'suggested' that problem might be with gauge

Indication is coming on 'idle' only, i have tested rpm at idle with A/C & without A/C and these are stable.

I have changed the sensor with new, problem still the same.

I just found out that 'at idle', engine temperature starts rising and when it passes 100C, oil pressure gauge starts fluctuating. when i pump in gas, revs go up .. temperature stops rising up and i don't get any indication. I did a road test of the truck for more than 2 hrs without going to idle and both temperature and oil level gauge were stable (temperature gauge was max at 02 points before 100 indicator). I pulled over to a parking lot and with in 5 minutes the temperature reached 100 and oil pressure low indication started to come.


Now, I have a couple of questions,


If oil pump is faulty, why i get the indication on idle and everything goes smooth on high revs

If only gauge is faulty, why the indication is relating to temperature

Does leak in differential has anything relation with oil level indicator issue

Thanks

1. You could have a weak/worn pump. Brother's old car was like that, low oil PSI at idle but once you got the engine RPM up a little bit it was enough to build the pressure even with the worn pump.
2. Don't think it is the gauge... but if you have low oil PSI, you could be creating more friction, which creates more heat (and more wear too by the way).
3. Differentials have nothing to do with engine oil. But I would fix any leak that you have.

Squeezmo
10-12-2010, 02:43 AM
Do not trust the gage. If you want to see your oil pressure you must hook up a gage.... the easiest place is at the pressure switch just above the oil filter.

There is no oil pressure sensor on the TB (try to buy an oil pressure sender or sensor... you can't... you hafta look up "oil pressure switch"). Just a switch the clicks to have the computer make you stop the engine... (to look real the PMC also makes the oil pressure gage go to zero when pressure drops below 16 psi and the pressure switch clicks).

Here is final summary of my diagnosis for the last two weeks


I handed over the truck to GMC, they were unable to diagnose and 'suggested' that problem might be with gauge

Indication is coming on 'idle' only, i have tested rpm at idle with A/C & without A/C and these are stable.

I have changed the sensor with new, problem still the same.

I don't get any sound whatsoever from the engine, i read in the forums that rattling sound should come if oil pump fails.

I just found out that 'at idle', engine temperature starts rising and when it passes 100C, oil pressure gauge starts fluctuating. when i pump in gas, revs go up .. temperature stops rising up and i don't get any indication. I did a road test of the truck for more than 2 hrs without going to idle and both temperature and oil level gauge were stable (temperature gauge was max at 02 points before 100 indicator). I pulled over to a parking lot and with in 5 minutes the temperature reached 100 and oil pressure low indication started to come.


Now, I have a couple of questions,


If oil pump is faulty, why i get the indication on idle and everything goes smooth on high revs

If only gauge is faulty, why the indication is relating to temperature

Does leak in differential has anything relation with oil level indicator issue

Thanks

Super 88
10-12-2010, 02:26 PM
Do not trust the gage. If you want to see your oil pressure you must hook up a gage.... the easiest place is at the pressure switch just above the oil filter.

There is no oil pressure sensor on the TB (try to buy an oil pressure sender or sensor... you can't... you hafta look up "oil pressure switch"). Just a switch the clicks to have the computer make you stop the engine... (to look real the PMC also makes the oil pressure gage go to zero when pressure drops below 16 psi and the pressure switch clicks).

:iagree:
I didn't remember seeing how many miles are on his engine. Maybe it is worn enough (thinking main or rod bearings) that the oil pressure is too low at idle - hence the switch opens.

To the original poster: what oil are you using and how many miles are on your engine? You said you had an oil leak when the technician didn't tighten the drain plug. How low did the oil get?

wdmalik
10-12-2010, 04:38 PM
To the original poster: what oil are you using and how many miles are on your engine? You said you had an oil leak when the technician didn't tighten the drain plug. How low did the oil get?

I have done approx 188,000 miles ... I use 10W30 oil in my truck.

At the time of leak, approx 1/2 oil tank was drained before i knew it.

wdmalik
10-13-2010, 04:48 AM
Still I am unable to understand the correlation between engine temperature and oil pressure. I don't get any issue until 100C. Whenever the temperature gauge shows 100C, oil pressure gauge starts fluctuating and DIC shows oil pressure low error.

Yesterday night, I kept running my truck on idle for about an hour and no error came. This morning I went to my office, in parking when the truck was idle for just 5 minutes and i started to get the error.

Sometimes, things are really strange and at the end you will find that error was occurring to a very unusual cause.

Super 88
10-13-2010, 09:39 AM
Still I am unable to understand the correlation between engine temperature and oil pressure. I don't get any issue until 100C. Whenever the temperature gauge shows 100C, oil pressure gauge starts fluctuating and DIC shows oil pressure low error.

It's very simply really. As the engine gets hot, the oil gets hot. As the oil temp increases the oil thins out. You will have less oil pressure with thin oil. Also clearances increase in a hot engine - especially in things like main and rod bearings. I've seen worn engines that have great oil pressure when they are cold, but once the engine gets to normal operating temp. the oil pressure will take a big nose dive and be outside normal limits.



Yesterday night, I kept running my truck on idle for about an hour and no error came. This morning I went to my office, in parking when the truck was idle for just 5 minutes and i started to get the error.

Sometimes, things are really strange and at the end you will find that error was occurring to a very unusual cause.

I'm not sure what type of "unusual cause" there could be. You basically have 2 possibilities:
1: Electrical problem (gauge, sending unit, wiring).
2: Low oil pressure at idle (worn engine, bad oil pump)

As someone said - you really need to get a "real" oil pressure gauge and see what the actual oil pressure is. IF it's normal then you can say it's an electrical problem. If it's NOT normal then obviously you have an engine problem.

To answer one of your previous questions: "If oil pump is faulty, why i get the indication on idle and everything goes smooth on high revs."
An oil pump could be worn so that it is not pumping enough at idle. Most all engines will have higher oil pressure at higher RPMs. But remember the gauge for the I6 engine is a fraud - it is nothing more than an idiot light. The numbers on the dash gauge doesn't mean a thing - other than you have enough pressure to close the switch which is about 12 - 16 psi (don't know the exact number and I've seen a couple different numbers on this forum).

Squeezmo
10-13-2010, 03:56 PM
at idle, the thinner oil at higher temperatures makes engine3 oil pressure operate near the bottom spec.

there is no oil pressure sender. Only a 16-18 psi switch that tells the computer oil pressure is low. The computer makes up where to put the gage needle vs temp and rpm... but the oil pressure switch overrides that and causes indicated pressure to go to zero (the needle falls and rises at the electronic rate... not at the actual oil pressure rate so you get wierd indications).

The sprung components in oil pressure switch can get weaker or clogged over time so it can take a higher oil pressure to cause the contact to reset and a lower pressure will allow the contacts to open.

Super 88
10-14-2010, 12:55 AM
at idle, the thinner oil at higher temperatures makes engine3 oil pressure operate near the bottom spec.

there is no oil pressure sender. Only a 16-18 psi switch that tells the computer oil pressure is low. The computer makes up where to put the gage needle vs temp and rpm... but the oil pressure switch overrides that and causes indicated pressure to go to zero (the needle falls and rises at the electronic rate... not at the actual oil pressure rate so you get wierd indications).

The sprung components in oil pressure switch can get weaker or clogged over time so it can take a higher oil pressure to cause the contact to reset and a lower pressure will allow the contacts to open.

All true, (and already mentioned by several others). But if you go back up to post 21 you will notice he stated: "I have changed the sensor with new, problem still the same."

wdmalik
10-15-2010, 06:12 AM
Guys,

First of all, many thanks for such detailed replies, appreciate it.

Yesterday I took my vehicle for a test drive, i drove it for about 200 miles. Things were great except when I came back and kept in idle for 20 minutes, as I started to get the oil pressure error.

I am pretty sure that oil pump is worn out, only problem is that my mechanic says that whole engine has to be removed from body to replace the oil and I am not comfortable with that. Still, I have to decide quickly because I don't want the engine to wear out internally due to low oil.

I wanted to hook up external gauge to find out the pressure. Only problem is that no one here is willing to do it and I don't know how to. I know that gauge can be hooked at oil pressure switch near the filter but I don't know how to make arrangement.

Anyways, that a lot to all of you.

wdmalik
10-18-2010, 04:25 AM
Well, I apparently decided to replace the oil pump. To my surprise, I found out that there is a 'base plate' welded to main structure which is holding the engine, so engine has to be taken out to replace the oil pump. Hence I handed over to my technician who told me that it will take approx 6 days to complete the job.

I will try to get the snaps, if I could. Lets hope that this is worth the effort.