1998 Ford F-150 P0174

Hello I have a 98 F150 and last year I noticed it started running a little rough. The exhaust had broke apart on the drivers side where the exhaust pipe turns down just before the cat. I noticed it was running like garbage ad the check engine light was on after but I continued to drive it as I didn’t have any time to work on the truck. A few weeks ago I was going to drive the truck to work and it would sputter when I hit the accelerator and the front end began to shake violently. The check engine light went from a steady light to blinking. I was able to drive it back home made it to work to look up what may be going on and it sounded like a hard mis-fire. I replaced all the spark plugs and I was able to close up where the exhaust had broke apart. It is brought back together but just held by some wire right now. I unplugged the battery to clear any codes and I took it for a drive and it ran better but still was sluggish when I hit the gas. I got an Autel code reader and the P0174 lit up.

Question is could this be from the 02 sensor or could the cat converter be junk? Any help would be helpful


Probably neither. It is lean condition. A P0174 is a bank 2 lean condition the computer can’t compensate for. Either the damaged exhaust is sucking in air or that bank 2 really IS lean. Likely a failing injector.

Thanks Mustangman

Is there any way I can diagnose a faulty injector or pinpoint which injector is bad?

Also I don’t know if it helps but I used the Autel AL319 to plug into the OBD. In the I/M readiness mode there was a red “X” next to CAT, EVAP, 02S, and HRT.

Until you get this properly fixed so there are no exhaust leaks, there is no sense trying to figure out all the codes you have.

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Yes, while the truck is idling, unplug each injector and note the drop in idle speed. When one cylinder doesn’t drop idle speed, its that injector. But like @It_s_Me says, until the exhaust leak is fixed, doing that test is pointless.

Modern gasoline engines just don’t run properly if there’s an exhaust leak. Especially a leak that close to the O2 sensor, before the cat. The engine computer would view that as a “overly lean” condition, b/c there’s too much oxygen hitting the o2 sensor. The oxygen in your case is coming from the outside air, and not from the engine, so there’s no way the computer can compensate. No point in speculating further until the exhaust leak is addressed. In fact I expect there’s an excellent chance that will entirely fix this problem

Hey guys thanks for all the info. I will get the exhaust fixed and fingers crossed that fixes the problems but you have given me some ideas where to start from there.

Thanks again.

Are you going to replace that broken exhaust manifold . . . or try to fix it?

Do you have a scanner that shows you live data?

If so, I’d be looking at the fuel trims for both banks. Could be the bank that didn’t set the code also has very positive values. Wouldn’t surprise me at all

In any case, if you have a scanner that does that, please let us know the fuel trims at idle after you replace that exhaust manifold