My girlfriend's 2001 Ford Focus (DOHC, Zetec engine, 110,000k on the engine) is having an ongoing series of problems, and I'm hoping someone can help me diagnose the issue (or at least back me up if I say, "it's time to take it in for repairs"). Here's the rundown.
The Check Engine light came on a while ago. From there, some relatively minor symptoms began to develop -- a slightly rough idle, and it started taking a bit longer than normal to warm up. I asked her when she had it in for a tune-up last, and it turns out the answer was "never", so I figured one was probably in order. Replaced the air filter, replaced the (original, came-with-the-car) spark plugs, checked the spark cables (fine), inspected the hoses (fine). I made a note to myself that the EGR looked to be in pretty rough shape (rusty), but otherwise, everything seemed to be in working order. Disconnected the battery to reset the CEL, fired it up, everything seemed fine.
It was less than a day before the rough idle began to return, so we swung by a parts store and got the codes. A generic EGR error turned up (not surprising), but there was also a misfire recorded on the 4th cylinder (surprising, I'd never noticed one). A bit of research
indicated that there's an extremely common sensor failure that plagues virtually all Focuses this age. I decided to try the EGR bypass, and on close inspection, I noticed that the top of the EGR valve was nearly rusted through in a few spots, and severely cracked. Sure enough, a gentle little tug on the hose at the top tore the nozzle clear off the EGR
. I felt pretty confident I'd found the culprit, so I finished off the ghetto bypass, and took a lap around campus to make sure the car was running fine. Sure enough, smooth as butter.
For a couple of days.
Since disconnecting the EGR, that misfire on the 4th cylinder has gone from "probably a fluke" to "fucking horrible", to the point that I had to abort a trip out to pick up a new EGR and sensor because the car was running so badly. It's fine at speed, but has an asthma attack while accelerating.
One last oddity that my girlfriend has noted; when the misfire happens, the radio goes to static for the duration of the misfire.
So that's pretty well everything up to this point. Could bypassing the EGR in any way
be contributing to the misfire? Or is the misfire probably an unlucky coincidence? Is it worth replacing the EGR/sensor and seeing if that helps the situation, or is it time to limp the poor car over to the mechanic's?