Well, I don’t feel that I’m on the right track. I’m ready to give it up, to be honest!
Yes, I had the battery disconnected when I made the above repairs. After reconnecting, I performed the “idle relearn” procedure, which I may perform again (there are several different procedures, each recommended by Ford).
Don’t give up. You will get it sooner or later. I think maybe you should recheck your steps. Pull out the coil again and check it for cracks. Could be a bad coil. Dont for get to check the PVC hose. There’s a hose that runs from it to the bottom of your engine (in the back of the engine). Right at the PCV valve is a little rubber elbow. Did you check this out. https://notsealed.com/ford-focus-rough-idle-with-no-check-engine-light-fix-diy.html
any new news on this ??
Yeah, it is sort of a puzzle what went wrong. I hope OP reports current status. Coil is presumably connected to ECM, so some chance ECM got zapped by a static electricity discharge during coil replacement. In high-tech electronics repair, the techs often wear a grounded carbon strap around their wrist to help prevent static discharge inadvertently damaging the equipment.
Given all the other stuff replaced, I wonder if OP tried replacing crank sensor?
See my answer to George in San Jose.
I more or less have given up. The car starts fine, but generally runs like crap. Gas mileage as I’ve reported is horrible, so I don’t go many places. I suspect the same thing you do: that the ECM somehow got nailed. The car is 20 years old, and I’ve put way more money into it than it’s worth, so I don’t know what I will do. Do you, by chance, know of a reputable vendor that sells EMC/PCMs preprogrammed to a specific VIN number. Does anyplace do such a thing? Thanks for checking in!
No, have not replaced crank sensor, but did replace cam position sensor (based on some strange symptoms). The new cam sensor did nothing for performance; no change at all.
Summit Racing website is where I’d look for a replacement ECM, if I couldn’t buy an affordable one from Ford, and couldn’t find one used from a parts recycler. There are generic ECM’s available I think, not geared to just one specific car/engine, something like that might work for your car. (May have emissions testing issue however, if your locations requires that.) If I had this problem however replacing the ECM wouldn’t be where I’d start. ECM failure not super-common. Fuel & spark would be my focus. I’d begin by testing that all the injectors are being pulsed (noid light), and that the spark is occurring consistently at the correct time (using a timing light and/or o-scope). Fuel trim test makes sense too. If those are ok, next I’d measure the cylinder’s compression.
If you don’t want to do all that, and just want to replace something, replacing the crank sensor makes sense. Measuring battery voltage when engine running is easy to do, should be 13-15.5 volts.
Is there a shop in your area that has the capability to test the ignition system using an o-scope? That sort of test could be very helpful in your case.
Just to butt in. I used to have a spare junk yard computer and coil with module just to be able to rule out those as possibilites when having a problem.
I understand the need to check for trouble codes and so on but really with diagnostic equipment, there is so much information to be gained by looking at the sensor outputs, etc. other than just codes. You can check engine temp being fed to the computer, the fuel trim, O2 response, etc. Just a wealth of information to a technician. Worth a couple hundred bucks for his/her time if a good diagnostician rather than just looking for codes.
I don’t see the coil as being the cause of a cold start problem at all and also do not think the coil replacement had anything to do with the problem. Is the CEL illuminated and/or flashing? You refer to no trouble codes but do not mention the light.
One thing you might consider is a large vacuum leak which I mentioned some time back. That can cause an engine to want to die when cold and which may (?) get a bit better when warmed up. That can kill fuel mileage, have an effect on the MAF sensor, and so on.
There are a number of possibilities including the pressure sensor and the possibility that the fuel injectors are not pulsing. No pulse would mean no run unless the injector grounds in the ECM are holding the injectors open all of the time. It’s easy enough to check. With the engine running stethoscope the injectors. You should hear them clicking away.
At this point I would not get too heated up about buying a replacement ECM.