So after trying to figure out why my truck isn't able to get to 65mph, I found a massive crack down the middle of my passenger side manifold. I can hear it ticking as well. After pulling codes I only got code 41 which is system running lean. Could the cracked manifold lead to the o2 sensor indicating the system as lean and cause my truck to lose power when trying to reach highway speeds? It has great low end power though. Any thoughts guy?

 

A cracked exhaust manifold will trigger a lean code. The unmetered air is interpreted as not enough fuel so the computer keeps dumping in more to compensate. So in reality your truck is actually running pig rich.

A rich fuel mixture will kill a converter in short time. Almost worse than a true lean condition IMHO.

 

I figured it would dump more fuel and technically run rich. Thanks for clearing that up for me bud. Would the issue cause me to lose power when trying to get accelerate if the crack is enough to throw a o2 sensor code?

 

Running rich kills power. It can ruin a converter in short order as well.

Is it THE root cause for your issue? Most likely. Replace that cracked manifold. You should also take a look at the converted while you are at it. A simple "rattle test" may confirm the converter is toasted.

Pull the O2 sensor to look for signs of contamination too. And the spark plugs.

 

I pulled plugs 1 and 5, they aren't wet or anything. If the air fuel ratio is bad then it's not too bad. Gonna replace it this weekend to get my power back. I'm not worried about the cat. Gonna remove it when I get the chance and put dual exhaust or just one exhaust pipe no cats

 

Also one thing I noticed is it won't throw a code until the truck is warmed up and I let off the throttle completely allowing air to get into the manifold

 

Computer runs in open loop until the engine is warmed up.

 

Oh duh haha. Thank you bud

 

I was wondering if the truck would run rough even in open loop before the o2 sensor realizes there's a problem? If my exhaust is the cause for my problems then shouldn't it only cause loss of performance in closed loop after being warmed up?

 

Long Term Fuel Trims are probably jacked to maximum values based on the O2 sensor readings over a period of time.

Fix what you know is wrong. The EFI system is just that: a system. A single component supplying erroneous feedback causes the entire system to adjust.

You could spend weeks analyzing this or use the Easy Button. Fix what you know is wrong. One less thing in the equation. Do not ignore the obvious.

 

will do. I'm getting the manifold replaced this weekend

 

So know we find out the O2 sensor isn't even plugged in....https://www.ford-trucks.com/forums/1...into-help.html

That does not imply you do not have to repair/replace that cracked manifold.

By the looks of it whom ever replaced that engine for you did a very sloppy job. Hard telling what other easter eggs are hiding.

 

haha yeah. I'm ganna go through all sensors and see which ones are connected as well. And I'm doing my exhaust manifold for sure. Now to find out where this other 2 wire plug goes into