Car came in with engine misfire, which only occurs from cold and last a few seconds, but if the engine is accelerated during the misfire, it clears and does not return. I've tried previously to upload PS data files but they are too big, hence I need to know how to cut sections of the recording for uploading.
Tests I've done...
A fault code read initially did not record any P codes only recording network codes. I exchanged the vehicle battery because another garage put a lead acid battery on. Since putting a silver calcium battery on the network codes have never returned.
When the engine misfired after this battery change fault codes PO303-00 cylinder 3 misfire detected, P2303-14 ignition coil primary "B" control circuit low, and P2300-14 ignition coil "A" control circuit low was recorded.
I started by completing the following tests...
Engine relative compression, all along the waveform the maximum peaks of current demand are all even.
Engine cranking compression tests using the WPS 500x. All compressions are approximately the same. A running compression test using the WPS does not show any obvious faults.
A crankcase test using the WPS500x does not show an increase in negative pressure at idle, nor does the crankcase pressure increase above atmospheric when the engine is accelerated.
Inlet manifold depression per cylinder records approximately 22" vacuum.
I could not see anything obvious, moving on...
I used the Power Probe to measure the resistance of the electrical wiring regarding the ignition circuits, and using the HOT SHOT function the wiring was loaded and passed. I tested the wiring several times and found no obvious faults.
I sent the ECU in for testing and after a week received a phone call saying thye tested the ECU, which recorded 1 ohm and nothing was wrong! I didn't go into it with them but a resistance test is not a load test and my confidence in the ECU being okay is sketchy?
Using the scope I tested the ignition coils power supply underload, which drops to about 30 mV. I've used two amps clamps on the ignition primary circuits and never once seen both circuits provide even current demands. On the latest recordings I can see current demands of 6A and 4A, also when the power transistor switches off in the ECU, and the current demand is switched off, the current goes negative as low as minus 7A. I'm not convinced that is correct and could be showing a poor power transistor operation, which can't be tested using an ohms test alone.
When the engine has misfired and I've managed to capture it on the scope, I've seen the ignition circuit secondary voltage significantly reduced, which has caused me to keep focused on the ignition system operation.
The injectors operation by comparisons allo look the same, but at some point I did remove the injectors and carryout a flow test. I was not convinced I liked what I was seeing! When the car drives there is no noticeable power loss, but the fuel spray didn't look brilliant? In fact the only test not performed is the fuel pressure, but because of the ignition voltage failing I didn't think the injector circuit would have an effect on that!
The other question I asked myself was, why if the injector circuits have a problem should the ECU record fault codes for the ignition and not the injection system?
I've reached the point that the only test left to complete is the fuel pressure test, and if that records okay, I'm not sure then which direction to go?
I found a Snap On write up on the internet with a very similar problem to mine, and their conclusion was the ECU, which fixed it when the exchanged it. A colleague of mine advised he'd had the same problem with the same company testing the ECUs and after several attempts at testing the ECU on his behalf and finding no faults, he purchased another ECU, which he then said fixed his problem.
I'm at a cross roads and not sure which direction to head off in now?
Anyone else had this problem with these Fiestas!!
Thanks for reading.