Mike McAteer

Hello everyone,

I bought this truck about two weeks ago from a used car dealer. A few days later I got code P0301 for a misfire on Cylinder #1 so we replaced the coil pack. I know I need new spark plugs since we checked them and they are pretty rough (are factory original with 167,000 miles on them.). I haven'r replaced them yet though. Anyways the same day we installed the coil pack I started to get the codes P0171 & P0174 for the system running too lean.

Since then I have noticed that the truck idles roughly and seems to lose "power" every few minutes. It seems to run fine when I am actually on the road driving but any time I come to a stop and am not accelerating the shaking starts. It even stalled out on me a few hours ago while I was waiting to pull out of a parking lot.

We did a visual inspection of hoses and don't see any noticeable holes or anything. We are planning to use a smoker to check for sure. We checked/blew out the fuel filter. We checked the fuel pressure at idle and it was 32 PSI not sure if that is normal or not though.

Just wanted to see if anyone could help point us in the right direction. Thanks!

tyoder59

Do you have a scan tool that you can read PIDS with? If so check to see if the lean condition is only present at idle. If so, it is almost certainly a vacuum leak. Check the PCV hose at the valve and the intake manifold, the rubber elbows have a tendency to deteriorate and leak.

Mike McAteer

Turns out you were correct about what the leak was actually caused by! It was indeed a leaky PCV elbow near the back. We hooked it up to a smoke machine and the smoke just poured out of it!

Unfortunately, now I am dealing with the P0301 misfire code which seems like it will never go away. We replaced all the spark plugs, replaced the coil pack on that cylinder and replaced the fuel injector and still have yet to get it to go away. The connector to the fuel injector that we replaced is kind of loose and wiggles because the clips on it don't seem to be working right (and were like that before it was replaced.) so we have a zip tie around the connector to make it tight against the injector to see if that could be the issue.

tyoder59

Anything electrical should set a coil primary circuit code. P0301 is a misfire code. Again, when the code is set is critical to diagnosis, ie ... idle, cruse, accel.. If you have a scanner with access to mode 6 data, it would be helpful.

F150Torqued

^^^^ X2. And study freeze frame data carefully trying to understand exactly what all is going on at the time the DTC is set.




Edit: Or something obviously out of whack. ie: air temp or barometer() - it is hard for the PCM to adjust things correctly if it thinks snow is on the ground or you are on top of Pikes Peak.

themike

Sir,I have a 03 4.6 w/157,000 and did as you.what I found was timing chain jumped a tooth on rt side gear causing it to lean.Sensor is on left side gear.replaced chain gears and guides.Part of guide broke off & stuck in chain causing jump. Master ford mech. did give advice after I changed all plugs injectors coils. Hope this helps, mike