SOLVED! Low oil pressure 4.2L

[TJBaker57]

One more quick question. Where did you mount the mechanical oil pressure gauge in the cab and how did you route the line to it?

I didn't really mount it at all, it just sits on the dash right in the lower left corner. There I can see it without taking my eyes off the road.




I used an adapter and some brass fittings to tap into the port on the front of the engine right near the oil filter. I used standard nylon tubing from Autometer and tiewrapped it up the dipstick tube then over the top of the engine tiewrapping it to the AC piping there. Once across I secured it along with a wiring harness that gets across to the left inner fender area between the battery and the fuseblock. Followed wiring harness back to the firewall and passed through the existing large grommeted wiring harness penetration.

Other members here have used electronic gauges.

 

[ironring]

I have an update on my oil pressure situation. I added some Lucas heavy duty oil stabilizer to my crank case. Since then (a couple of weeks ago) the truck has been running great and I have not had the oil pressure gauge drop once, even after 90-minute highway drives. Time will tell, but so far I am sold!

 

[Ilikemy3s]

After reading this I am starting to worry about the oil and oil pressure issues in my truck. 2005 SWTB 4.2L bought her in 2015 with 85K miles on it now at just over 266K. Always used Mobile 1 oil and filter but will admit to going by the OLM for oil changes until recently started changin @ 3-5K. Hope I am not on borrowed time.

 

[Mooseman]

I have heard some bad things about the Lucas additive, one of them being that it makes the oil aerate more. Not so much of a concern in gears like the diff but in an engine can be bad. Could be that the viscosity gets bumped up and increases the pressure that way. I know it did in my Saab's 5.3 before I replaced the oil pump with a high volume and pressure unit.

 

[TJBaker57]

After reading this I am starting to worry about the oil and oil pressure issues in my truck

I find that having added an actual mechanical gauge gives me a far better chance of catching an actual low pressure condition instead of worrying about a fake dashboard gauge.

Also understanding that this engine is NOT like our older engines and is not designed to have what we are used to seeing in terms of oil pressure at idle. The pressure switch activates at just about 4 psi I have found in tests of a handful of switches. And the minimum specification for the 4.2 is just 12 psi at 1200 rpm.

 

[Aroc]

I will admit I have once or twice tried 10w-40. It is not advised by the owners manual.

My circumstance is a 2002 with 280000 miles and a leaking oil pickup tube O-ring. I installed an aftermarket mechanical oil pressure gauge. Additionally, as a 2002 model these 4.2 engines have an oil temperature sensor that I can monitor with an OBD2 adapter and a phone app.

If my oil temperature rises above about 190 to 195°F that is when I will have a low pressure situation at idle. Like yours I see 8 to 10 at a normal warm idle.

My idle has always been a steady 620 or so.

It is worth noting the service manuals state the test specification for oil pressure is 12 psi at 1200 rpm. Well at least that is what my memory comes up with.

On high milage engines with increased tolerances this low oil pressure at idle seems to be prevalant.

However, your engine is on the high end of wear and mileage and may have increased tolerances, allowing more oil to pass by the bearings

I am interested in what OBD2 system you use to monitor your oil temperature. I may look to add a system to monitor this as oil temp and pressure typically inversely follow,

It should be noted since @ironring replaced the pickup o-ring and had no effect in oil pressure it may just be engine wear/oil path tolerances as primary cause. Just my

 

[TJBaker57]

interested in what OBD2 system you use to monitor your oil temperature.

In my case I use one of several smartphone apps with a bluetooth OBD2 dongle. I have Torque Pro, Car Scanner ELM OBD2, OBDFusion, DashCommand, Chevrosys, Car Gauge Pro (OBD2 + Enhance).

Only the 2002 model year 4.2 LL8 engines have an engine oil temperature sensor.

Other members here have installed aftermarket combined engine oil pressure and temperature gauges.

 

[Aroc]

OK. Great.
Sounds like the combo oil pressure and temperature gauges is the way to go.

I'll have to look futher into the OBD2 optiions you mentioned.
Any preference for multifeature user freindly model with graphing capability.

Thanks.

2002 GMC Envoy, 153,000 miles.

 

[TJBaker57]

Any preference for multifeature user freindly model with graphing capability.

All these apps need customization for the vehicle make/model etc. All these apps benefit from user entered data parameter definitions.

None are real user friendly but for graphing capability my hands down favorite is Car Scanner ELM OBD2. It records whatever data you display while driving and can easily review that data with graphing right in the app. No need to be trying to watch the screen when you should be watching the road. And no need to be fiddling with log files, spreadsheets and the like.

 

[TJBaker57]

Any preference for multifeature user freindly

As for adapters this one is proven...

https://www.amazon.com/dp/B011NSX27A/?tag=gmtnation-20

 

[Ilikemy3s]

Has anyone had to have their 4.2L oil pan dropped for service? If so, what did it roughly cost? I ask as I was thinking on doing it to mine to not only have it cleaned out, but also check on the oil pick up as well as the bearings. Thoughts?

 

[mrrsm]

One of Our Members (Kevin Nadeau) once produced a Five Part Video Series on YouTube titled "How to Remove The Oil Pick Up Tube in my GMC Envoy". Like your vehicle... Kevin's is a 4WD, too ...with all of the issues that THAT brings along with doing all of this work.

While he was doing all of this Hard Labor... He also memorialized his MISTAKES that Badly Damaged his Crankcase Oil Pan by him failing to remove the Two Rear-Most positioned Oil-Pan to Engine Block Bolts that remain hidden underneath those Two Rubber Plugs fitted in between the Front of the Bell Housing and the Rear of the Engine Block... But why talk about what he has so eloquently documented for us all .... in Pictures?

Part 1... is ONLY The Beginning...

 

[Mooseman]

It's truly a PITA of a job. I've done it and I'd rather drive it off a cliff than doing that again. Look for my thread on timing chain replacement in the FAQs.

 

[Jon!]

I want to thank everyone for their help! The pictures and information really helped me. I was able to get the oil gauge Out with a bit of struggle (by a bit I mean a lot; it was hard to get the gauge screwed in) My pressure was around 16-18 at idle and around 40-50 when driving down the road (didn’t go too far, 35-40mph at most during test). I believe cleaning the throttle body is what solved the issue for me. Hopefully everything stays that way. I wasn’t able to reproduce the low pressure warning issue no matter how long I idled, so I am very happy!

I have been able to flush the trans, change the oil, rear differential, (power steering is my next thing), and clean the throttle all on my own using the forum and ytube videos. I’m very grateful!

Note for anyone that reads this thread in the future to get help: my symptoms were that my message/warning only came on when I turned the key into the on position but did not start car and left it that way for about a minute or so. Otherwise, it was rare to get the issue at all, but if I did get it at any other time, it was at a stop sign or red light when the engine would idle for a minute or more. I switched out my oil pressure switch (no change really) and did an amsoil motor flush + oil change (helped for bit of time before issue came back). I don’t doubt there is sludge in my engine though. I can see the grit and debris in the valve cover when I pull it out just to replace any oil. I will be doing more flushes with each oil change in the future, and hopefully over time, it will clear out little by little.
Thanks again!

I do not have the words to express how grateful I am for this post and thread! I experienced the same problem - low idle, low engine oil pressure, same warnings. I cleaned the throttle and my idle RPM increased from 500 to ~625 and my oil pressure did not drop while driving back and forth to work. Also, my check engine light went off. I have a 2006 Chevrolet Trailblazer with a 4.2L I6 - mileage over 218,000. Would you recommend using heavier oil (i.e. 20/50 instead of 10/40)?

 

[Mooseman]

No. Stick with the stock weight. The VVT system is sensitive to the oil used.