L92 low hot oil pressure at idle HELP!!!!

[Actifenpleinair]

I bought this used via a used car dealer / the Manhiem Auction in PA and a Cadillac Dealer trade in in PA. the unit was originally in colorado with a rental comp.....

Not sure i would use lower viscosity in winter, our modern ECM controlled engines warm up quickly to thermostat temp, and stay there. Let your motor warm up 3-5 minutes and drive gently first 20 minutes and your 5w30 dexos-1 oil will be fine. (My 333k mile Trailblazer and 279k mile yukon denali will vouch for this throughout N. Vermont, mountains of UT, ID, WY, NV, and CA)
.....EDIT.... I just read the 10 psi warm in drive, and that is low, though if you are using the dash gage and not an OBD sensor live data or TorquePro, it might be higher than you can guess on dash guage.
I just did a new cam sensor, pickup tube o-ring (old one was fine, po replaced at 168k w/ Melling m365 oil pump which showed virtually NO wear), timing gear, chain, tensioner, cover, gasket, and oil pump inspection and relief valve shim on my 279k mile L92 '07 yukon denali for under 200 in parts from rockauto and on the ground in my garage through the timing cover. I took out the 4 front oil pan bolts loosened the rest to drop the front of oil pan about a half inch... left oil in pan and all but 5 quarts of fluid in cooling system, which came out when I removed water pump. I did NOT want to deal with drop steering rack, differential, axles, crossmember and oil pan shenanigans.
Slow and steady you can coax the pickup tube 10mm nut off with a spanner, magnet and patience, wiggle off the oil pump, and get to timing parts for arefresh. YouTube is your friend.
I went up from 14 psi to 16 hot in gear with 5w30 dexos-1 and am at 35+ psi hot at 2000 rpm, I am good with that until it drops down below 12 or so. I would go with about .300" of shim (washers) versus the .095" I used to see if i could get a few more psi, though the new oil filter bypass valve I will put in at oil change might help enough.

 

[Actifenpleinair]

Is is possible that the gauge is not accurate?

My oil pressure sender was dead on at 240k when I put a new one in (a pain!) I would use an obd scanner live data to see if it goes from near zero engine off to 50's psi cold and in 40's hot 2k rpm, then watch as it falls to the low point at hot idle in gear. If it reads a range and reacts to throttle clips, it is working fine. Spend the money on a cheap obd2 bluetooth plug in and load up Torgue Pro on your phone or tablet or ... here is what I set up as a monitor screen on TorquePro.

 

[Campie]

Yes, oil analysis is next and I’ll up it from 5W 30 to 5W 40 til we get a better idea of what the issue really is.

Hummm… no and no to your suggestions. I’ll look into both! Thank you!

So, looking at your two other suggestions: we don’t have an oil consumption problem. We have a low oil, pressure problem so I’m not sure the valve cover would help, but I will certainly check it out and replace it if needed. For the torque converter, we have absolutely no problem at all with power, even when towing. The problem is getting off the highway, stopping at the top of the exit ramp with less than a half a tank and 90° outside. Also, not ruling out the ignition switch which someone else mentioned. Just thinking oh things that makes sense for the problem at hand. Although, I totally understand that we do not understand, lol! Thanks everyone!

 

[rdezs]

That's interesting that it only acts up when under half a tank? You might want to monitor your fuel pressure in real time while you drive around.

 

[Campie]

That's interesting that it only acts up when under half a tank? You might want to monitor your fuel pressure in real time while you drive around.

Yes, just not sure how to do that. Bought a scanner but I’m not sure yet how to use it or what all it does. It’s an XTool IP500 and is supposed to be bi-directional and monitor real-time etc. Really feels like vapor lock…

 

[rdezs]

I actually haven't ever seen one of these with vapor lock. The fuel systems under enough pressure to raise the boiling point, and routed far enough away from the exhaust.

I'm inclined to suspect the fuel pump is starting to act up on you. At the age of the vehicle, I would plan on changing it regardless. I started showing similar symptoms but not completely stalling, I think it was around 175,000 miles..... But apparently the mileage is irrelevant, GM has a TSB about keeping your fuel tank at a quarter full for a minimum.... It gets below that, the fuel is what cools the pump, the pumps get hot and their life is shortened.

Even if you plan on replacing it as preventative maintenance, I would still do a pressure check to see exactly where it stands. If you do replace, use only a genuine GM or ACDelco. If not available, Delphi is the next good option. Rockauto.com is your friend here.

A complete diagnosis is always the preference before shooting off the parts Canon.

A viable option for the less tech savvy person, is to pay the average $180 shop rate..... For no more than a 1 hour diagnosis at the dealer. (It will probably take them less than 30 minutes, but they charged the one hour minimum usually)

That way you can attack the specific cause yourself with confidence, then address preventative maintenance items afterwards.

 

[Fless]

Yes, just not sure how to do that. Bought a scanner but I’m not sure yet how to use it or what all it does. It’s an XTool IP500 and is supposed to be bi-directional and monitor real-time etc. Really feels like vapor lock…

That scanner will show Live Data, so select the fuel pressure PID and have someone watch it while you replicate the issue. IF it will graph that PID, do that and you'll be able to see how/if the fuel pressure varies over time.

 

[Campie]

That scanner will show Live Data, so select the fuel pressure PID and have someone watch it while you replicate the issue. IF it will graph that PID, do that and you'll be able to see how/if the fuel pressure varies over time.

I actually haven't ever seen one of these with vapor lock. The fuel systems under enough pressure to raise the boiling point, and routed far enough away from the exhaust.

I'm inclined to suspect the fuel pump is starting to act up on you. At the age of the vehicle, I would plan on changing it regardless. I started showing similar symptoms but not completely stalling, I think it was around 175,000 miles..... But apparently the mileage is irrelevant, GM has a TSB about keeping your fuel tank at a quarter full for a minimum.... It gets below that, the fuel is what cools the pump, the pumps get hot and their life is shortened.

Even if you plan on replacing it as preventative maintenance, I would still do a pressure check to see exactly where it stands. If you do replace, use only a genuine GM or ACDelco. If not available, Delphi is the next good option. Rockauto.com is your friend here.

A complete diagnosis is always the preference before shooting off the parts Canon.

A viable option for the less tech savvy person, is to pay the average $180 shop rate..... For no more than a 1 hour diagnosis at the dealer. (It will probably take them less than 30 minutes, but they charged the one hour minimum usually)

That way you can attack the specific cause yourself with confidence, then address preventative maintenance items afterwards.

We already did replace the fuel pump last fall and that did not cure the problem. It has done this three times since then. I don’t have the paperwork handy so I’m not positive they replaced the fuel pressure sensor but I think they did. Where is the fuel pressure sensor?

 

[rdezs]

We already did replace the fuel pump last fall and that did not cure the problem. It has done this three times since then. I don’t have the paperwork handy so I’m not positive they replaced the fuel pressure sensor but I think they did. Where is the fuel pressure sensor?

If you look under the vehicle about where the driver seat is, you will locate your fuel line on the inside of the frame rail. Follow it, and you'll find the sensor that screws in and has a harness plug on it.

 

[Campie]

If you look under the vehicle about where the driver seat is, you will locate your fuel line on the inside of the frame rail. Follow it, and you'll find the sensor that screws in and has a harness plug on it.

Is it possible that the sensor is bad?

 

[Campie]

That scanner will show Live Data, so select the fuel pressure PID and have someone watch it while you replicate the issue. IF it will graph that PID, do that and you'll be able to see how/if the fuel pressure varies over time.

Nice, I’ll figure out how to use the scanner!

 

[rdezs]

Replacing that sensor is typically not something they do when they change your fuel pump.

Live fuel pressure data on your scanner reads from that sensor. When you first turn the key on but don't start the engine, 58 to 60 PSI is normal. After it's running, drops down to like 43 to 45 PSI.

A fuel pump on the way out might drop down below 43 PSI. And the initial pressure might be higher or lower than 58 to 60.

Post some data on what it's doing????

Not exactly sure why, but I've seen multiple instances where the fuel pump is on the way out, only putting out 35 PSI, and no check engine light or trouble code.

 

[Campie]

Replacing that sensor is typically not something they do when they change your fuel pump.

Live fuel pressure data on your scanner reads from that sensor. When you first turn the key on but don't start the engine, 58 to 60 PSI is normal. After it's running, drops down to like 43 to 45 PSI.

A fuel pump on the way out might drop down below 43 PSI. And the initial pressure might be higher or lower than 58 to 60.

Post some data on what it's doing????

Not exactly sure why, but I've seen multiple instances where the fuel pump is on the way out, only putting out 35 PSI, and no check engine light or trouble code.

But, we did already replace the fuel pump and I’m sure it was with a GM/AC Delco part. That was last fall, and it did not cure the problem. And, the problem does seem to be happening more often. We are out camping now for another week, but the investigation will continue when we get home!

Is there anyone in or near Akron, Ohio? We would love to learn more in person!

 

[rdezs]

I'd still check the fuel pressure. Even OEM parts sometimes go bad sooner than expected.

See what the fuel pressure is doing so you can rule it out. Then check your EVAP system, particularly the purge valve on the intake to rule it out. See what your fuel trims are doing also. I would also suspect the throttle body....

 

[Campie]

Yep, once we get back from camping.

Here’s what’s been done recently:
MAF and filter
Battery cables and cleaned the grounds
PCV
Vapor Canister Purge Valve
Fuel pump - last fall, did not help!

Battery check is next then maybe fuel pressure sensor and cam/crank sensor. Need to keep it simple as we’re NOT mechanics! We have a Transit van that pulls the camper but the Yukon is so much more powerful we’re hoping to figure out the issues and use it instead of the Transit. More in a week or so when we get home. Thanks!

 

[rdezs]

Add EVAP vent valve. It opens when the engine is running to pull fresh air in, while the engine draws in fuel vapors stored in the canister. Bad vent valve... Can create a vacuum in the tank if stuck closed. (Countering the fuel pump suction, according to physics.....might reduce fuel pressure)

 

[Campie]

Add EVAP vent valve. It opens when the engine is running to pull fresh air in, while the engine draws in fuel vapors stored in the canister. Bad vent valve... Can create a vacuum in the tank if stuck closed. (Countering the fuel pump suction, according to physics.....might reduce fuel pressure)

Ok, more parts to locate on the car… where is this EVAP vent valve? Or is that the same as the vapor canister purge valve?

 

[rdezs]

The purge valve is located on your intake manifold. The vent valve is right there next to your carbon canister, with a hose that goes up into the body work near the fuel filter hose, where it draws in fresh air when the valve is open. The vent valve usually comes with new hoses, and connects to the carbon canister.

 

[rdezs]

Note: it's a good time to proactively change that carbon canister, and check for loose carbon pellets while you're there already.

 

[Campie]

Note: it's a good time to proactively change that carbon canister, and check for loose carbon pellets while you're there already.

Already did the purge valve so is this what we need next?