We have a 2003 SES with the DOHC
24v Duratec engine that my daughter drives while she is at college. Engine has only 40-45k miles, yet the check engine light came on recently. It has been misfiring at low RPM
(at idle) and start ups are a bit rough (may take a second crack to get started)
She went to Autozone to get the OBD-II codes pulled; they pulled a P0303 and P0316 trouble code. While their printout indicated a cylinder #3 misfire (P0303) and a crank sensor condition (P0316) [the Chilton list P0340 as the crack position sensor code]
, the manual does not list a P0316 in the OBD-II code table.
Elsewhere, I have found that the P0316 is an Engine Misfire Detected on Startup (First 1000 Revolutions) problem, which seems to make sense since the car is rough at start-up. This weekend I was able to check out the coil pack, check the plug wires, replace the plugs with OEM
Motorcraft, and then put everything back together using dielectric to protect the electrical connections.
Here is what I found with the coil pack:
<blockquote>Primary resistivity in the range of 0.6-0.8 ohms (Chilton manual indicates a spec of 0.5 with no range)
Secondary resistivity in the range of 10.2-10.9k ohms (Chilton manual indicates a spec of 13.5k ohms with no range).</blockquote>
Plug wires had continuity with the following resistivity:
<blockquote>Cyl 1 4.81k ohms
Cyl 2 4.36k ohms
Cyl 3 4.96k ohms
Cyl 4 8.31k ohms
Cyl 5 9.08k ohms
Cyl 6 10.42k ohms</blockquote>
These values seemed to make sense as they were proportional to the plug wire length. After putting everything back together car still seemed to start a bit rough and at low rpm
(e.g. at stops) would "skip a beat" periodically and in her words "vibrate".
She indicates that the check light has came back on after a couple of trips within 24 hours of getting it back together. She is concerned that she might be doing permanent damage to the car by driving with the light on.
I also replaced the air filter, cleaned the MAF
sensor and the EGR
valve while I had those off (needed to pull the intake mani to get to the coil pack and back bank of plugs ... they don't make it easy do they!). She has not gotten back to Autozone to get the codes pulled, but I am expecting to get the same set.
Here are my questions/suppositions:
1) What could be possible root causes of a P0316 code coming up.
2) Am I right to think that if I resolve the P0316 issue the P0303 ought to take care of itself?
3) If a coil was getting weak wouldn't I expect to get two misfire codes on the companion cylinder to #3; is it safe to rule the coil pack out as a root cause?
4) My plug wires seem to be in goof shape; is it safe to rule them out of contention.
5) Lacking any other suggestions, is this narrowing down to a possible plugged injector on No 3 cylinder? If so what is a good way to clean it without pulling the rail off (remember, this one is on the back side of the engine on drivers side).
Welcome any thoughts and suggestions ... I wish I had a real time OBD
sensor for this [and my 2001 Expy which also seems to want to throw off low EGR
flow codes no matter what!]