I am having trouble diagnosing a hesitation in a friend's vehicle and could use some help from someone much more experienced than myself.
It's a 2001 16V Zetec automatic with 165K that has started throwing CEL 301 (Cylinder 1 misfire codes). My friend told me that the vehicle would hesitate at around 40, then proceed up to highway speed then throw a CEL.
I asked her about the history of related repairs and learned the following;
- Replaced coil pack less than 3K ago
- Replaced fuel filter 3K ago
- Replaced plugs and wires 1.5K ago
- Replaced PCV valve 4K ago
Someone was throwing parts at it to correct this problem, but it eventually got worse.
The vehicle had also been exempt from the dreaded Focus fuel pump recall back in 2003. All fuel flow at low speed under load as well as high speed seem to be within tolerance. There seems to be no falter except at around 40 MPH.
Since it was still getting worse and there were no local viable repair options available, I decided to take on the issue. I tested spark at cyl 1 and found it to be strong, eliminating the wires and coil. I pulled the plug and as a platinum plug, it still looked new. This left two things, the injector and an internal problem like a valve..
Without a compression tester (MIA) and the overall smooth operation of the motor in every other condition, I took the injector route. I pulled the fuel rail and replaced the cyl 1 injector with a remanufactured one. I also replaced gaskets on the TB and the intake. While I was in there, I also replaced the DPFE sensor as I have heard of silly readings being fed back to the ECU to create a similar issue with a leak somewhere..
The overall condition from my friend is that things are much smoother and better (No CEL's) but she did mention that there is still a hesitation at around 40, although less than before.
My only guess at this point without a shop manual is that there is a vacuum leak somewhere. Next I would assume that a vacuum leak could cause this, but still not sure why at a certain speed range like 40 MPH with AT.
As I'm at a loss and hate throwing money at parts in hope and find my compression gauge MIA, but feel very close at this point, I would appreciate any advice to help out my friend..
Thanks in advance for your advice and help..