Low pressure all of a sudden

[mijohnst]

I might have just done something dumb. I added Seafaom to my Tahoe's oil last night. I'd done it to my other Yukon and had no issue. It was about 1/2 a quart low and input a full can of Seafoam in which likely overfilled it. It drive fine to work but I noticed at lunch that the oil pressure is now at zero. When I'm driving though it will go up to nearly 10.

It seems to idle fine but a few times it felt like the engine was about to stall when accelerating from a stop, but didn't. My plan is to get it drained when I get home and put in new oil and filter. I just recently put in a new oil pressure sensor So I don't think that's it. I praying I didn't just wear out my oil pump though. Engine temperature stayed normal the entire time.

Any thoughts?

 

[OR VietVet]

You may have cleaned enough dirt/grit with the Seafoam that you have clogged the new sensor. That is a WAG.

 

[Scottydoggs]

oil and filter change asap, like at work in the parking lot. never put that in the oil, gas tank and in a vac line is fine, never the oil.

 

[mijohnst]

By WAG you mean a guess? lol

 

[mijohnst]

oil and filter change asap, like at work in the parking lot. never put that in the oil, gas tank and in a vac line is fine, never the oil.

Yikes! That is bad! I'll never believe youtube again!

 

[OR VietVet]

Yikes! That is bad! I'll never believe youtube again!

Trust here before you trust you tube. The "WAG" is a Wild Ass Guess!

 

[iamdub]

Best case, the Seafoam freed up some chunks of sludge that clogged the sensor and you actually have more pressure than that. Worst case, it freed up enough sludge to clog the filter or pickup tube.

Like they said, change your oil before you drive it next cuz if there is a problem, that may be the last drive. The inconvenience of changing the oil at work is far less than the inconvenience of replacing the engine.

After the oil change, I'd suggest cutting open the filter to see if it's clogged to try to have some sort of an answer. You'd also get an idea of how nasty it may be inside your engine. If this prompts you to do so, you could pop off a valve cover to get a pretty clear idea and how you should proceed.

Going forward, you want to gradually dissolve sludge/buildup to remove it instead of trying to chemically break it loose in chunks.

 

[Tonyrodz]

Best case, the Seafoam freed up some chunks of sludge that clogged the sensor and you actually have more pressure than that. Worst case, it freed up enough sludge to clog the filter or pickup tube.

Like they said, change your oil before you drive it next cu if there is a problem, that may be the last drive. The inconvenience of changing the oil at work is far less that the inconvenience of replacing the engine.

After the oil change, I'd suggest cutting open the filter to see if it's clogged to try to have some sort of an answer. You'd also get an idea of how nasty it may be inside your engine. If this prompts you to do so, you could pop off a valve cover to get a pretty clear idea and how you should proceed.

Going forward, you want to gradually dissolve sludge/buildup to remove it instead of trying to chemically break it loose in chunks.

What's a good way to gradually break up the sludge?

 

[mijohnst]

I really appreciate all the advice. As suggested I got a ride home after work and drove back with all my oil change equipment. Drain all the oil in the place the filter. I let it run for about 5 minutes and oil pressure came up to about 20 psi. That's about half what it normally is. Drive it home (2 miles) and it seemed to drive okay despite having low pressure, and a few times that it seemed to choke up for an instant and then pick back up. I let it sit for last 30 minutes and just went out to see, and now I'm back at it 10psi it won't idle without me pushing a little gas. Uggg...

So my question is this, would the oil pressure sensor cause the engine problems? When I first got this Tahoe it was pegged at 80 psi. Last month I changed it and it went went back to normal. I didn't buy an oem, so I wonder if it went bad already and it reading low oil pressure is causing the engine to not run correctly.

I also ran codes on it, and I'm seeing P0101 and P0640 which say the mass airflow sensor needs to be replaced. I've never seen that error before. Would that sensor just go out all of a sudden then engine to sputter? I don't know if the sensors actually affect the engine as a safeguard, or they just come up as warnings.

 

[OR VietVet]

I would change the sensor again with an AC Delco one. I am not sure but when you are at idle and in gear the pressure is lower and for some strange reason the system is trying to protect the engine buy trying to shut the engine down. Like a LIMP IN MODE. I could be way off base. If I was trying to break up sludge I would do a 1/2 quart of trans fluid and change the oil and filter again after running that for about 15 minutes at close to idle. That doesn't mean I am right, it just means I am trying to come up with a way to bring pressure back to what you are comfortable with.

 

[HiHoeSilver]

What's a good way to gradually break up the sludge?

High quality full synthetic/filter and "frequent" changes.

 

[Tonyrodz]

High quality full synthetic/filter and "frequent" changes.

2000-2500 oci?

 

[iamdub]

What's a good way to gradually break up the sludge?

High quality full synthetic/filter and "frequent" changes.

2000-2500 oci?

What Nate said. I wouldn't base it off mileage, go by the appearance of the oil since it's gonna get darker with the more crap it removes. You can use gentle additives to help, but most any quality synthetic oil is gonna have a decent detergent package in it. Maybe you can use a cheaper oil since you'll be changing it more frequently but add a known good cleaner. Just don't use a full can so it's not full strength if it's strong stuff. Kreen? Motor Medic? Kerosene?

 

[George B]

If you have an engine oil cooler on that truck you may want to change the oil one more time. I imagine there was some residual diluted oil in the cooler. That might help bring the pressure back too.

 

[HiHoeSilver]

What Nate said. I wouldn't base it off mileage, go by the appearance of the oil since it's gonna get darker with the more crap it removes. You can use gentle additives to help, but most any quality synthetic oil is gonna have a decent detergent package in it. Maybe you can use a cheaper oil since you'll be changing it more frequently but add a known good cleaner. Just don't use a full can so it's not full strength if it's strong stuff. Kreen? Motor Medic? Kerosene?

I've put Kreen in my oil before.

 

[iamdub]

I've put Kreen in my oil before.

I know that's one of the known good ones. Then again, if your motor isn't so gunky in the first place, you won't have anything to break up and cause problems.

 

[HiHoeSilver]

I know that's one of the known good ones. Then again, if your motor isn't so gunky in the first place, you won't have anything to break up and cause problems.

Truth. With an "unknown" cleanliness factor, slow and steady wins the race.

 

[OR VietVet]

Truth. With an "unknown" cleanliness factor, slow and steady wins the race.

I knew a girl like that once. Just once.

 

[iamdub]

I really appreciate all the advice. As suggested I got a ride home after work and drove back with all my oil change equipment. Drain all the oil in the place the filter. I let it run for about 5 minutes and oil pressure came up to about 20 psi. That's about half what it normally is. Drive it home (2 miles) and it seemed to drive okay despite having low pressure, and a few times that it seemed to choke up for an instant and then pick back up. I let it sit for last 30 minutes and just went out to see, and now I'm back at it 10psi it won't idle without me pushing a little gas. Uggg...

So my question is this, would the oil pressure sensor cause the engine problems? When I first got this Tahoe it was pegged at 80 psi. Last month I changed it and it went went back to normal. I didn't buy an oem, so I wonder if it went bad already and it reading low oil pressure is causing the engine to not run correctly.

I also ran codes on it, and I'm seeing P0101 and P0640 which say the mass airflow sensor needs to be replaced. I've never seen that error before. Would that sensor just go out all of a sudden then engine to sputter? I don't know if the sensors actually affect the engine as a safeguard, or they just come up as warnings.

How'd the oil look when it came out? Thick? Any chunks?

I don't think the PCM would shut off the engine with 0 psi. I think it should as a safety measure, but I believe plenty of people report driving around with their gauge either pegged or at zero because of a faulty oil pressure sensor.

I'd clean the MAF since it's an easy first step and clear the code(s). A faulty MAF could cause engine sputtering. The engine will run with a dead MAF sinc the PCM will cut it out of the loop and reference a speed-density map as a fallback. If the MAF is failing intermittently while driving (or if there's an intermittently faulty connection in the harness, particularly at the plug), the sputtering may be the PCM switching to the speed-density table while the engine is running.

 

[mijohnst]

How'd the oil look when it came out? Thick? Any chunks?

I don't think the PCM would shut off the engine with 0 psi. I think it should as a safety measure, but I believe plenty of people report driving around with their gauge either pegged or at zero because of a faulty oil pressure sensor.

I'd clean the MAF since it's an easy first step and clear the code(s). A faulty MAF could cause engine sputtering. The engine will run with a dead MAF sinc the PCM will cut it out of the loop and reference a speed-density map as a fallback. If the MAF is failing intermittently while driving (or if there's an intermittently faulty connection in the harness, particularly at the plug), the sputtering may be the PCM switching to the speed-density table while the engine is running.

The oil looked fairly dirty but I didn't see any chunks come out of it and I watched it completely drain. It is the first time that it's been changed since I purchased it in December and I'd been meaning to do it. As a matter of fact, that's why I used the Seafoam yesterday. I planned on just running it on my short drives to work (less than 5 miles round trip) and change the oil Saturday day morning. So much for that. Before I screwed it up it had been running like a top. :/

I pulled off the MFS tonight and thought I could swap it with my 2004 Yukon just to see if that was the problem, but the Yukon is a FlexFuel and this Tahoe is not so the connector would not fit. Should I just go buy a new one? It doesn't look that dirty to me, but what do I know? Even the air filter looks pretty clean. I'll probably just replace them all just to be on the safe side.

My only other idea is to unplug the battery and maybe that'll reset the PCM? As Ron put it though, it's a WAG. lol

Also, I went and looked and I'm not crazy! Even the Seafoam website says to put it in your crack case and it won't hurt the engine. I'm guilty of putting more than the recommended, however. I'm starting to think the Seafoam incident is a coincidence and something just happened to go out...hopefully, the MFS.

https://seafoamsales.com/how-to-add-sea-foam-motor-treatment-to-gas-and-diesel-crankcase-oil/