Just looking at the wiring diagrams - they show “Load Relay” and “Aux Load Relay” - location left component panel under left dash panel. Are these what you mean?
Frankie
The report of gauges and/or instruments lights being affected when you have a misfire suggests it could be a wiring or ground fault behind the instrument panel.
It is a puzzle the misfire is under load, that will usually suggest a fault in the ignition amp, or the high voltage part of the ignition system.
In this case it might be vibration under load that affects the wiring.
Or it could be that at high loads ( and high RPM ) the ignition circuit is drawing more current and there is high resistance in the wiring which causes voltage drop and hence causes a fault.
I would run the ignition direct from the battery for a trial. Make sure the ground connection for the ignition amp is good.
No. On the V12 with the Bosch alt, there’s a “Load Dump Module” (I think) on the RH wheelwell that is connected to the alt. I have never understood what it does, but a couple of owners have diagnosed faults by simply disconnecting it and their problems went away. Since the alt isn’t really germaine to the number of cylinders but rather to the model year, I thought maybe your car might have the same gadget – in which case I was going to suggest you disconnect it and see what happens.
Had another go at it today. Removed instrument cluster and then printed circuit - no sign of any corrosion, wiring or ground fault either in the instrument pack or the electrics behind; visually checked the ign switch wiring - OK.
Started engine - misfires immediately on idle but no dash lights or chime - on opening drivers door lights come on and chime sounds; close door and lights/chime go off but misfire continues (may be coincidental). On pressing throttle misfire goes away and returns on idle.
Turned on interior lights when misfiring - no flickering in bulbs.
Wiggled wires and looms in engine bay particularly servicing injectors and coils during misfiring on idle - no difference. Disconnected/reconnected some sensors to note any change. After about 15 secs following CTS disconnection engine dies altogether (never done this before). Happened twice. On third time re-started engine and now idles smoothly - disconnection of CTS results in slightly higher idle but engine continues idling smoothly. Again - possible co-incidence?
Turned on electrical load when idling smoothly - all well and HRW relay does not drop out.
Still idling smoothly so took for a test drive. Random misfire on acceleration, even during the same acceleration test. Now the seat belt light and chimes don’t come on at all - even when they should (but warning light does glow when ign on and engine off).
Not sure where to go from here……………………
Frankie
How old is your battery?
Those miscellaneous lights coming on still has me thinking there’s a power issue at hand. I’ve had my share of stalls, but it never lights up the dash like it is on yours.
I know that battery tests well, but I’ll tell you, the car is very sensitive to crap batteries. Six months before my battery is going to fail, my passenger door lock won’t auto-lock/open. Then other weird things happen. The battery tests well, but as soon as I swap it out, all problems are resolved.
I just realized you never specifically provided any codes that were pulled.
Can you please provide the codes that are being pulled up? All of them please.
Thanks.
Fair comment. Just over 2 years/4,000 miles old.
F
There were no codes - but I’ll plug in and make a note of any/all again.
F
Result:-
MIL status - OFF
Codes found - 0
Monitors OK - 5
No stored codes found
No pending codes stored.
F
That’s another oddity right there. You are getting misfires, but no stored codes.
Any chance that you could swap the oxygen sensor plugs, just for the hell of it? Plug the Bank A into the Bank B plug, and vice versa.
I have another guess when you’re done checking the oxygen sensor…swap out the ECU Relay.
That’s hidden under the passengers side kick panel, just under the passenger airbag. I believe its a blue relay. Swap it out with other ones, I think they’re all the same.
This is a 6-banger, you know.
Swapped the battery this morning - just in case. No change.
At “off” battery voltage is a steady 13.3 volts. On idle with the misfire the voltage at the battery terminals jumps around between 13.8 and 14.6 and has been as low as 12. The volt gauge needle on the dash also flickers (other gauges remain steady). This suggests to me that either alternator charge is getting to the battery intermittently or there is an intermittent heavy drain - hence swapping the alternator was a reasonable suggestion but unfortunately didn’t cure the problem.
I don’t think a bad ECU relay or wrongly connected o2 sensors will affect battery voltage in that way - it seems to me to be more like a making/breaking contact or earth, or a breakdown of insulation. Also, the fact that both engine and dash board equipment is affected at the same time suggests that the fault is common to both systems and therefore unlikely to be wiring or a component connected to only one of these systems.
Happy to hear any reasoned opinion to the contrary…………….
Frankie
Yes, us 6-bangers still have two separate banks of exhaust coming out of the engine. Perhaps I should have called it “Bank 1 and Bank 2”
Both options I gave you are free of charge and should take you less than 5 minutes to try…each.
I’m not even sure why you think the ECU relay couldn’t cause issues like this!
If the misfire slows the engine enough the alternator output will drop and not charge the battery. Does the drop in voltage match the drop in engine RPM ?
The ignition circuits and everything else should work with a voltage dropping below 12V which is what happens when you crank.
Something has changed if you no longer have strange instrument cluster events when the misfire happens. Was that after playing about behind the instruments ?
Engine rpm hardly alters during misfire - around 750 from memory. Started up again just now and idles with misfire continuously, but warning lights and chime come on a off (same lights every time) - probably 5 seconds on and another 5 off but irregularly and I’m not doing anything - just standing beside the car. This time battery terminal voltage remained steady at 14.4 - 14.5. The symptoms are so random/variable without touching anything that it is impossible to link anything you do to an effect on the car.
I’ll try VEEkays suggestions but I can’t see the connection between the relay and the sensors with the effects on the car.
More later……………………
Frankie
Took longer than expected because my wiring diagram and the cars handbook give different locations/colours for some relays. However………
Swapping the o2 sensor plugs - no change.
Swapping the ECM control relay (light blue on blue) - no change.
Didn’t swap the other relay here (EMS power relay - Silver/red on white) because it is different to the others and I couldn’t find a match elsewhere on the car.
So.……………………….?
Frankie
Thank you. Can you post a video of what’s going on? It’s bizarre that you are getting misfires without at least a generic p0300 code popping up.
I’d like to hear the engine and see the dash lights blinking.
The fact that there was no change when you swapped the oxygen sensor plugs…it should have either gotten better…or worse? No change may indicate the car is not reading, or reacting to the oxygen sensors on the car?
I was thinking of a video myself - but will need to get technical assistance (probably wife - I’m not “up” with media).
I have had 02 sensors fail before with no effect on performance/running at all - just sooty plugs and emissions test fails. Even so, I have difficulty seeing a link between rich/lean running and dashboard seatbelt and washer fluid warning lights.
It may be a while before I can do the video……………
Frankie