Hello F150 world. This is my first post so I apologize in advance if this topic has already been covered, I couldn’t find anything that pertained to my current situation.

I have an 02 F150 XLT 5.4 v8 4wd that just rolled over 200k. Truck is in “pretty good” shape for 200k and Michigan rust. It’s been a good truck so far at least. I’m a 3rd year med student and need this ol girl to last me a few more years so I’m trying to be proactive.

About a month ago, my brother in law, who is a mechanic, and I replaced the passenger side exhaust manifold since I had bought it with a hole and just dealt with the noise until now.

Truck has run fine besides the manifold noise, until about 2 weeks ago I noticed I’m getting terrible gas mileage (about 12 mpg) much worse than before the manifold fix. I also noticed a super small oil leak (a few drips only sometimes) after I drive it and smell of oil after I put it in park and idle. But this is only like 1/5 times I drive it. And also today after turning the truck on with the engine cold, the RPM started to bounce (see video)

I am wondering if any/all of these are related issues since they all started about the same time?

I am hoping the oil leak is just a valve cover gasket, the oil still smells like oil and exhaust still smells like exhaust and coolant levels are normal so I’m not too concerned for head gasket

the fuel economy I have no idea besides maybe upstream 02 sensor got fried when we were heating the manifold bolts? Or the IAC or MAS?

also wondered if maybe a vacuum leak? Since it has also been a little power lacking at highway speeds.

any and all help is welcomed I really need to keep this baby goin. Thanks in advance!

 

Your video is not there.

Have you checked it for codes?

 

yeah I just noticed that the video didnt load. Im working on it now. It threw a "Fuel bank 1 Lean" before the manifold, then reset the ECM and it has not thrown any codes. I am using Forscan to check.

 

Then you have a vacuum leak. That would explain your conditions. PO171, I assume?

 

Check the elbow on the PCV probably has a hole in it

 

yup that was the code. I assumed it was due to the manifold since it has not come back since the fix.

 

will do. thank you for the quick replies everyone

 

Exhaust leak isn't vacuum. Vacuum will be on the intake side. Check the PCV elbow, like Raybz said. That's the most common leak on these... BUT, it usually also triggers PO174 with PO171.

 

yeah so my logic on the code was it was losing the positive flow thru the manifold showing a false lean mixture. But will definitely check the pcv. Thank you for your help

 

Just how big was the leak?