Engine Revving in Park

[ugadawgs311]

Last week I received an “Oil Pressure Low” warning on my 2007 Z71 Tahoe (about 177k miles) while driving. The engine seemed to run ok with no issues. I checked the dip stick, and oil was low, so last night I added two quarts just the same as I usually do. When I turned the car on this morning, it was definitely jumpy and the RPMs seemed higher than normal, but the car was still drivable. After about 1.5 miles (maybe 5 minutes) of driving, I received an “Engine Power Reduced” warning. I was unable to accelerate, and eventually rolled into an adjacent parking lot.

I turned the car off and on, and the engine now revs up while still in park (as if I’m pushing the accelerator). I tried driving for about 50 yards, but the same warnings came back on along with traction control issues and stabilitrak issues.

What could be causing this? Maybe the throttle body? Is it related to the recently added oil, or just a coincidence? Any help is greatly appreciated!

 

[Geotrash]

Last week I received an “Oil Pressure Low” warning on my 2007 Z71 Tahoe (about 177k miles) while driving. The engine seemed to run ok with no issues. I checked the dip stick, and oil was low, so last night I added two quarts just the same as I usually do. When I turned the car on this morning, it was definitely jumpy and the RPMs seemed higher than normal, but the car was still drivable. After about 1.5 miles (maybe 5 minutes) of driving, I received an “Engine Power Reduced” warning. I was unable to accelerate, and eventually rolled into an adjacent parking lot.

I turned the car off and on, and the engine now revs up while still in park (as if I’m pushing the accelerator). I tried driving for about 50 yards, but the same warnings came back on along with traction control issues and stabilitrak issues.

What could be causing this? Maybe the throttle body? Is it related to the recently added oil, or just a coincidence? Any help is greatly appreciated!

Almost certainly a coincidence with the oil. The only way to troubleshoot this though is with a scanner that can read GM-specific codes, such as a Tech 2, which you can get from chinacardiags.com for about $250. If you're on an even tighter budget, this one is pretty good:

https://a.co/d/0SZ5xJs

 

[ugadawgs311]

Thanks. So sounds like the oil isn’t the issue. I’m hoping just a sensor or something small like that.

Edit: any chance it could be computer related?

 

[Doubeleive]

sounds like multiple problems
low oil pressure could be oil pickup tube (or worse)
engine revving is something different, possibly the throttle body is goofy or even stuck open
how often do you do maintenance? when was the last time you cleaned the throttle body, intake, changed the air filter?

 

[ugadawgs311]

I just had it in the shop about a month ago to fix the throttle position sensor. That was giving me a check engine light, but there were no noticeable signs when driving. The overnight engine reving, stabilitrak, TCS errors came out of nowhere.

The guys at the shop didn’t mention anything else needed work while I was there (not 100% confident they checked though).

 

[Doubeleive]

I just had it in the shop about a month ago to fix the throttle position sensor. That was giving me a check engine light, but there were no noticeable signs when driving. The overnight engine reving, stabilitrak, TCS errors came out of nowhere.

The guys at the shop didn’t mention anything else needed work while I was there (not 100% confident they checked though).

probably need to take it back to the shop then

 

[Rocket Man]

This^^^. And I wouldn’t drive it until you find out what’s wrong especially if it’s revving up in park like you’re stepping on the accelerator, just putting it in drive while the engine is revving can damage the trans. No use making more trouble.

 

[ugadawgs311]

Thanks everyone. After checking the dipstick, it looks like the oil is way over filled (well above the five dots on the dip stick). Hopefully just draining and changing the oil will be the fix.

 

[AEChevy]

Hey, what about the Mass Airflow sensor stuck open. Or Intake manifold air pressure switch to high...

 

[Doubeleive]

Hey, what about the Mass Airflow sensor stuck open. Or Intake manifold air pressure switch to high...

nah, it wouldn't make it rev up, it would make it shift weird and gallop like a horse maybe or maybe not even start or start and then idle down and die

 

[Doubeleive]

you could probably pull the air intake off the throttle body and take a look at the butterfly and see if it is stuck open or something, should be closed with engine off

 

[Doubeleive]

if it is revving up on it's own with no pedal applied you can pretty much bet money on the throttle body or pedal sensor but less likely.

 

[Caddylack]

I checked the dip stick, and oil was low, so last night I added two quarts just the same as I usually do.

This is a very concerning statement.

You should not be running that low on oil on a regular basis. That's how you blow up your engine prematurely.

 

[Rocket Man]

Thanks everyone. After checking the dipstick, it looks like the oil is way over filled (well above the five dots on the dip stick). Hopefully just draining and changing the oil will be the fix.

That shouldn’t be any issue at all. You can safely run a quart or more over without any problems.

 

[ugadawgs311]

Thanks, everyone. Finally got it into a shop, and it was spitting out a ton of codes. One mechanic had the idea to take off the mass airflow sensor (or some part of that system), and suddenly the revving while idle seemed to stop. They're going to start with replacing that sensor in the morning. My fingers are crossed that that's the only issue and nothing more serious. We'll see.

 

[ugadawgs311]

This is a very concerning statement.

You should not be running that low on oil on a regular basis. That's how you blow up your engine prematurely.

Yeah thinking back on it now, I don't think I've ever added 2 quarts at the same time, so that was likely overkill. I've definitely had moments where it needed a top off before completely changing the oil though.

 

[Doubeleive]

Thanks, everyone. Finally got it into a shop, and it was spitting out a ton of codes. One mechanic had the idea to take off the mass airflow sensor (or some part of that system), and suddenly the revving while idle seemed to stop. They're going to start with replacing that sensor in the morning. My fingers are crossed that that's the only issue and nothing more serious. We'll see.

i doubt it is the maf, when it is unplugged that puts everything else in default because it can't tell how much air is going thru the intake.
but not impossible i guess, that would be a really weird one I have seen them cause all kinds of other problems but not engine revving. the shop should be able to test the maf.

 

[George B]

It would be nice if you could post up the list of codes it had.

 

[Rocket Man]

I don’t have much faith in a mechanic that diagnoses a problem by unplugging something, seeing a change, and deciding to replace that part because of that. Ask for the codes at the very least so we can help you gain an understanding of what might be going on. It’s good for you to be educated on what the possibilities could be so you can make educated decisions. Don’t just take the word of someone trying to make money off a customer who doesn’t know better. You have a lot of knowledge here available for free.

 

[ugadawgs311]

I don’t have much faith in a mechanic that diagnoses a problem by unplugging something, seeing a change, and deciding to replace that part because of that. Ask for the codes at the very least so we can help you gain an understanding of what might be going on. It’s good for you to be educated on what the possibilities could be so you can make educated decisions. Don’t just take the word of someone trying to make money off a customer who doesn’t know better. You have a lot of knowledge here available for free.

Great advice, and thanks for the tip. I’ll be sure to ask for the list of codes tomorrow. I appreciate all the help!