F150online Forums - 06 5.4L V8 Lariat Low RPMs under load/Stalls when stopping

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06 5.4L V8 Lariat Low RPMs under load/Stalls when stopping

2006 Ford F-150 Lariat 5.4L V8 Flex Fuel With 221,000 Miles
The issue i am having is that when you come to a stop the rpms drop down into the 300's. This sometimes leads to it stalling out, especially if I just tap the gas and then hit the break right away. If i slip it into neutral the rpms return to the factory range of about 600-700. But as soon as I put it into gear and there is a load on the engine they drop to the high 400 low 500s. I just replaced both the camshaft position sensors hoping they had something to do with it but no luck. One thing i noticed tho is when the truck does stall out the low oil pressure warning lamp comes on and it takes an extra second to fire back up. But after it is running again oil pressure is at normal range. I have an Edge CTS 2 unit so I am able to monitor all of my engines data from fuel rail pressure to intake air temperature and everything in between. Hopefully someone can give me a solid direction to look in so im not on a wild goose chase trying to hunt down the issue.

I have a DTC for Bank 2 efficiency below threshhold, I have a bad cat and its been bad for a few years without casuing any driveability issues. I have also noticed that the problem gets worse as the engine reaches operating temperature. Any and all input is greatly appreciated. Thanks

Here is a quick update with where I am at. I replaced both of the Camshaft Position Sensors with a good improvement in how the engine runs and a major reduction of the amount of valve ticking the engine is known for. Unfortunately no luck with the RPM issue tho. Then I went and replaced both of the VCT Sensors, this showed major improvement on how the engine runs and the remaining valve tick has been completely eliminated. One thing I noted while replacing the VCT Solenoids was that on one of them the screens on the bottom portion of the solenoid were gone and are presumably in my engine somewhere. I am hoping that since they were made of a fragile plastic and a very small metal screen that my engine chewed them up and caught them in the oil filter. If it didn't then I am wondering if they may be still inside the engine and clogging up an oil port somewhere causing my issue. Any input and ideas are greatly appreciated. Thanks.

Are you sure your bad cat isn't partially plugged? Excessive backpressure can cause it to run bad.

Quote:

Originally Posted by glc (Post 5263179)

Are you sure your bad cat isn't partially plugged? Excessive backpressure can cause it to run bad.

Thats the thing it doesnt run bad. I get good power and have no bogging or RPM issues when I am pressing the throttle. It is only when stopping or stopped that I have a problem with the RPMs dropping too low and that is what is leading it to stall sometimes. I would think if it was the CAT then I would notice performance issues when I am getting on the throttle or at any other time other than idle.

Clean the throttle body if if hasn't been cleaned lately.

Quote:

Originally Posted by Roadie (Post 5263188)

Clean the throttle body if if hasn't been cleaned lately.

Thats my next move. I am about to go grab some Throttle Body Cleaner right now and get into it. Ill post an update when I am done to share progress. Thanks

Make sure you do it correctly to avoid damage! Watch this video:

https://www.f150online.com/forums/vi...ttle-body.html

Quote:

Originally Posted by glc (Post 5263191)

Make sure you do it correctly to avoid damage! Watch this video:

https://www.f150online.com/forums/vi...ttle-body.html

For some reason I am unable to view the video. But I will be sure to look up the correct way to clean an electronic throttle body. Thanks for the input it is always very much appreciated.

try this link

Here's a direct link to YouTube, jusr remove the 2 spaces:

h ttp s://youtu.be/JPNnHU6PYbo

Problem solved!!! Luckily it wasn't a faulty torque converter or transmission or clogged oil port. I pulled my throttle body off today and it was packed with soot and grime. Took me almost an hour with a plastic brush and 2 full cans of throttle body cleaner to finally get it cleaned. Re-installed it, cleared the DTC’s and disconnected the battery for 5 minutes to clear active memory and took it for a long enough drive to get it up to operating temperature and to get the oil temperature at maximum and the RPMs remained steady in the 550-600 range without dropping. So after spending hundreds on new camshaft position sensors and VCT solenoids all I needed to do was spend $10 on throttle body cleaner and spend an hour cleaning it. Thank you to everyone who posted their 2 cents!

Thanks for letting us know what fixed it!

Quote:

Originally Posted by Bluejay (Post 5263255)

Also clean the MAF

I will keep that in mind but as of right now the truck is running better than it has in years. I should have taken a picture of the throttle body to show you guys the amount of gunk that built up in there. I was honestly amazed the truck could even run and that the idle under load was the only issue. I am not sure how to clean the MAF but I will look up how to do it and take care of it. Thanks again for everyone's input in helping me diagnose and repair this issue!