gamessr71

I just had check engine light code read from my 2004 F-150 truck with 116,00 miles on it. The Auto Zone print read out read out says Code PO174 "System to lean Bank 2". Suggested parts are to replace the intake manifold gasket. The truck idles and runs great. No coolant leaking issues,no misfiring or overheating problems. What test can I run to double check to see if the gasket is leaking before I commit to the expense of having the intake manifold gasket replaced? Should I be concerned about any damage to the engine by ignoring this?

F150Torqued

YES. The computer is lengthening injector pulse width on that bank (injecting more fuel - effecting your fuel economy). It will lead to fouling spark plugs and misfires (which dump unburned fuel into Catalytic converters and causing them to overheat. Too much of that will melt the honeycomb).

dukedkt442

With vacuum leaks like that, I've usually seen vehicles also throw the P0171 bank 1 lean code as well if the leak is part of the intake. With just a single bank, you could have a faulty upstream O2 sensor on that bank, or a leak at the exhaust manifold.

Either way, it must be repaired.

redfishtd

To track a vacuum leak you can build a cheap smoke machine off youtube .I did in-order to find leak that mechanics had given up on . It took a year for me to finally make the decision to do it . A new metal paint can with lid ,shrader air valve , /clear 6 foot tubing/3/4 inch to brake booster hose /some cigarillos taped to a piece of tygon inside can making it in series with out put tygon fitting in lid . The idea is to light the cigar /close lid quickly /have air attached at 1-2 psi and watch smoke travel up clear hose and watch for leaks .The cigar will burn quickly ,it took me 3 tries before smoke came up under battery, a defective purge valve was under there . Of course engine is not running for smoke test,keep can away from truck . All fittings were in lid of can and yes I bought a new paint can . Some guys use a 5 gallon plastic can with sand in bottom ,but can could melt if not done right .Some guys put rags in throttle body to stop smoke from coming out breather . Two sets of eyes and help would be nice ,I did it by myself .
If I tried it again I would try cotton cloth with some mineral oil on it instead of cigarillos . Of course have some water /fire extinguish handy . There are other ways this was mine .
You can try a propane torch unlit to wave around near likely leaks and engine will speed up /improve . How ever you try it be careful .

dukedkt442

Lights out with a flashlight helps being able to see the smoke.

Remember to pull the MAF and plug the whole, MAFs don't like smoke.

BareBonesXL

What engine? Since you only have one bank showing the code the problem is probably not huge yet. There's probably a pending code for the other bank. The PCM and O2 sensors will keep the fuel mixture correct. The code means that the PCM has to add more fuel to get the O2 sensor reading correct. But it's still correct, not rich or lean.

If you get a scanner and read live data you'll know about the problem. Sometimes it's a cold engine problem only, due to cold seals and gaskets. Once warmed up it's fine. Live data will show that.

The IMRC bushings leak sometimes too.