Fuel injectors and ECU

[oxbrain]

I have a question. My engine is still running really rough and I am running out of ideas as to the cause. It idles smoothly, but the plugs are soot covered and there is very little power available. Step on the gas and it just hesitates like crazy.

Something I realised though. I am using the capri injectors with the festiva ECU. If the capri injectors are bigger than the festiva injectors, then wouldn't the base fuel maps be wrong, and the car would run very rich?

After maybe 10 minutes of driving I got a CEL code 17, O2 sensor failure. Could this be because the mixture is so rich it just assumes the o2 sensor is faulty?

[mooseheadc]

if your O2 sensor is also sooted up, it can make things worse, as its insulated: this
can give you that CEL.

have a digital volt meter? you can test the O2 sensor. take out the sensor, put in a vise.
clamp the neg lead to the sensor case with wire or a hoseclamp, and the other to the sensor output.
should readaround .3V

Now heat with a torch, so its HOT.

the sensor should put out just under 1 volt. take torch away, should drop quick.If it doesn't, get new one.

it only runs off those base maps at start, and then at near WOT, Open Loop mode. Otherwise its off the learned maps and O2 feedback

With too big injectors, this normal shows a rich crapply idle, but goes away on the street.


You might have a bad fuel regulator, too.

Its possible to fake out the ECU with a bogus O2 sensor signal, by using a radio shack pot set
as a voltage divider to .9V, a fake 'Rich' reading (note this trick is sometimes used in ob2
cars to fake the rear, post cat sensors, wired to .3V for Lean)
By the way, you can mess up you ECU doing this, just so you're warned.

Anyway, forcing it to 'Rich' see if you notice engine running better.(Note for testing,
don't do this for long) If its still bad, you got something dumping extra gas in,
either faulty FPR or Injectors leaky, or even just too big.

[oxbrain]

The o2 sensor is brand new. One of the problems is that the header I have on there is a 4-2-1, and the o2 sensor is only looking at 1-3, not 2-4. #4 still doesn't seem to be heating up, and I can't figure out why. The header paint is discoloring uniformly on the other three cylinders, but not on #4. The other three plugs are getting sooty, but not #4.

Right now the car has such low power that it can barely accelerate. At idle it's fine and seems to have plenty of torque. You can give it a little gas and still have smooth power. Give it a little too much throttle and it starts stuttering and missing. This seems to just get worse the more load you put it under. I tried swapping in the 323 ecu to see if that had better base maps, but it seems to act the same.

I found another problem. When I made my injector harness I was pushing the test probes into the injector plugs. Now the contacts inside are bent up and might not be making good connection. I'm soldering on some spare capri injector plugs to see if that makes any difference. I am also swapping in some spare injectors.

[oxbrain]

Big improvement. Apparently something was wrong with the injectors or plugs. New plugs soldered on and the spare injectors and it's running a LOT better. I'd say it's up to stock power, maybe a smidge more. It still has really bad hesitation and there's still a lot of power missing, but atleast it's running better. Tommorow I'm going to unplug the 323 ecu(can't let the inspector see it dangling), get the car teched, then continue troubleshooting.

I think I'm still smelling some gas in the exhaust, so I think it's still running rich. The header is finally starting to discolor on #4, so it's obviously heating up now. I think the next step is going to be to replace the plugs since they're pretty sooty, replace the distributor cap since it's old, run some injector cleaner through it, seafoam it, and then give it a longer drive to see if the ecu can fix the fuel maps. I'm going to try and get the day off work, if I can I'm going to stop by a junkyard and grab a second festy injector harness and some 323 injectors/plugs.