This has plagued me since early March. cylinder 4 is not firing in simple terms. Things I've done so far; - Tried secondary CAS, ECU and AFM - Replaced all spark plugs and #4 injector (o-rings and everything plus sent rail off to a specialist for cleaning) - Replaced all injector connectors with Bosch quick releases and even tried a new OEM connector on #4 but nothing (yes, injectors are all corrosion free) - injectors all OHM out correctly - replaced O2s - Injector pin on #4 has constant 12v - Tried new set of coil packs - re-crimpted the OEM crimp points in ECU footwell. - checked coil pack connector which voltage is in spec. - all earths on plenum are tight, even went to the liberty of adding additional earths - ignition timing is at 15 degrees btdc verified with timing light, new temp sensor, TPS 0.45v idle, idle is around 800rpm all wiring plugs in engine bay corrosion free and lubed with di-electric grease. I've tried basically everything I can think of. The injector ticks doing the screw driver trick but a lot less sound comes from it in comparison to other injectors. I'm out of ideas, would love to get this fixed. The car doesn't feel low on power (I'm guessing the ECU is adjusting for that non firing cylinder but idle is lumpy and no change to idle when spark to that cylinder is removed. Help me out guys!
Have you swapped the injector from another cylinder? Would rule out the injector itself. If it ticks but not that powerful as the rest and it still doesn't work properly after swapping another injector in you'd be left with the wiring. Something could also be wrong with the ecu though unlikely, try one from another car.
There are only 3 things that will prevent a cyclinder from firing which is fuel, spark and air or more specifically cylinder compression. To check spark, pull the coil pack out and put a known working spark plug in the end and earth out on the plenum and hook the wires back in. You can bump the key a few times to check for spark but I recommend taking out the CAS and with the harness plugged in turn the spindle slowly until you see a spark. Just for reference pull out number 3 coil pack and plug and set up the same as number 4. Because the firing order is 123456, when you see #3 spark you know #4 should fire next. If you have Nissan Datascan or NIStune, turn off the fuel pump while you do this. With the procedure above do the same for the injectors, obvioulsy without removing them you will hear each one click but put the pointy end of a screwdriver on top of the injector body and the handle on your ear. Finally, throw a compression gauge on this cylinder and do a compression test. Unless you have at least 80PSI you will not hear a difference when you carry out a load test. SIM300 was plagued with starting issues for a long time and turned out to be very low compression from (if I remember correctly) bent valves.
Tried another PTU? Continuity back to the ECU all good for injector and spark? Have to dig out the schematic. There is a good coloured one floating around here that helps a lot. Easy to follow. Also, try what Karl said, makes it easier if you know what you are trying to fix.
Didn't we test this when you where over here? Didn't I do a balance test with Consult and number 4 didn't make much difference?? refresh my memory ??
I'll try the other tests ie CAS out today when I touch the car. I'm still suspect it's electrical, would low compression mean the spark plug is completely dry when I pull it out when all the other cylinders have fuel scent wet spark plugs? Pulled out cylinder 4s spark plug last night which I replaced a month ago, and it was completely clean looking exactly how it did when I put it in. Will also get my hands on a compression tester. Tekky, the balance test on cyl 4 was intermittent when you were testing. It would cut in and out. Now 4 months down the track, it is completely dead.
Third for compression test. Have you checked the earth side of the injector loom? Power is all well and good but the injectors are linked to the drivers in the ECU by an earth switch.
Try another PTU. Check the 6 coilpack wires between PTU and coilpacks AND between PTU and ECU all measure the same resistance. It should be low - between 1 and 3 ohms or so. When you do this check, have both the ECU and PTU unplugged so you are only measuring the resistance of the wire, not the electronic components at either end. Also, are all the PTU connections clean? <-- check this first
Your comment here leads me to believe its an injector issue. I had a similar issue to this once where I lost three injectors at once, turned out to be the ECU. You mentioned earlier that you can hear the injector clicking but less than the others. If you are doing this with the engine running this can easily be mistaken for noise conducting through the metal from neighbouring items. Pulling the CAS out like I mentioned earlier will give a definite indicator If it is working or not.
Yep I'm suspect it's the wire to the ECU also. Unfortunately didn't get the chance to touch the love machine today. I'm a complete newbie to multimeters however I do have one as it is a necessity. A friend helped me check the OHM rating on injectors directly but how would I check the wire from the injector to ECU? I stumbled across this article which makes sense; http://forums.nicoclub.com/test-injector-wiring-t483658.html So I'd disconnect battery, remove connector from ECU, link up pin 112 (cyl 4 injector) and pin 58 (common) to multi meter?
You want to test the wire. So, for injector 4... Disconnect battery Disconnect ECU Disconnect injector 4 Connect one lead to pin 112 on ECU plug Connect other lead to each pin of injector plug. 1 pin will give you 2 or 3 ohms, the other should give you an open circuit. If you are unsure of the reading, do other injector wires to compare. 1: 101 2: 110 3: 103 4: 112 5: 105 6: 114 Lastly, injector common is pin 58, but there is no point in checking that this time as an issue there would affect all injectors.
Always try the basics as already discussed by others. I had a cylinder not firing and i was convinced that the coil connector was faulty. It was the injector connector wire that was faulty so the balance test on the coil connector also made no difference when disconnected. If you have no compression in the offending cylinder you would be wasting your time changing and swapping. You have not said whether you have compression yet. Test this first and you may be surprised. If this checks out then you can test for more complex issues. Guessing is both wasting time and frustrating not to mention costly. MichaelZ
Thanks Dave for that useful info! You make a fun mod. Okay, haven't done CAS or PTU or compression test yet, but I am onto something with my multimeter. Testing cyl 4 injector switched earth pin 112 on ECU with injector plug gives me open circuit on both pins Just to confirm, I also tested with cyl 2 pin 110 and some ohms appeared Could it be that I have diagnosed my issue? the ground switch wire on the injector is broken? Guessing the quick fix is to run a new wire from the ECU direct to the injector? Maybe it would be a good time to just replace the whole engine wiring loom since the current one isn't best. All happy to source it, but how hard would it to be installing the loom with engine in? I am happy to remove dash.
Running a new loom with engine in is not too difficult but it is time consuming. In my opinion if you can afford it, do it! It will save you plenty of potential issues down the track as these cars seem to fail from numerous electrical issues due to aged wiring looms. New connectors and new wires is the best thing, just make it easier on yourself later by changing out the injector connectors for quick release items before you install it.
