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It would’nt cost anything to pull the EGR valve, clean it and put it back. Ignoring everything else previous to this if it stuck open at idle the engine would stall. It’s worth a shot and things are getting desperate.
Just a thought, but when it goes crazy it goes completely mad, what we used to call full scale deflection. Have you looked at the earth/ground leads. It’s almost as if the earth/ground fails and then it tries to ground out through whatever is avaliable to pass current. This is just a wild guess without thinking about it too much.
Back in the day, there used to be a small earth lead on the back of the block, this went to the chassis. It was very much a minor item, but, leave it undone when doing a motor changeover or similar and the engine would earth out through the nylon lined clutch cable. This would go really hot and melt the steel clutch cable to the nylon liner. Technically this could be called a real bitch.
Do you think that it could be possilbe, that the fault you’ve found could have resulted in a contaminated cat. converter which is influencing the fuel trims via the post cat. O2 sensors.
But congratulation on finding the fault, I hope you go ahead and buy a Hantek 8Channel, I’ve never regretted bying mine although it sits in the tool cuppboard most of the time. I have used the square wave generator to track down wiring to find out which wire I’m dealing with when the colours change within the loom.
OK, so we know the air filter is not influencing the fuel trims, so I feel confident that this can be ticked off, as we move into the engine we get to the MAF………….
Can you hook up a DVOM to the MAF and take some readings – at KOEOFF KOEON then at idle and next see what happens at WOT (Wide Open Throttle). I just have a feeling that you could be right about the MAF over reporting, I have an aversion to spending money on parts until I am absolutley sure that I am replacing a dud part.
Re you looking for a broken baffle inside the intake manifold, its possible but I would think that if it broke internally there would be a permanent and definited influence to one or more cylinders. I remember years ago a Diesel Truck had a loss of Power when it was opened up under load/high speed, much was tried and eventually it was found to be a bit of the air intake trunking flapping shut when the air flow was high then springing back into place when the load was off. If the exhaust was strangled it would most likely be in the cat which would show in the post cat O2 sensor. The exhaust backpressure should be almost nothing (measured before the cat and maybe less after the cat). If you have a compound pressure gauge well and good, in years past we used to drill a tiny hole in the pipe to see what the leakage was. With a blocked or partially blocked muffler it used to hiss out as if it was an air compressor. No backpressure gauges in those days. Then we sould repair the hole with a self tapping screw. Ah those were the days, one could stand on the footpath and diagnose cars as they drove past.
Google: Symtoms of a Blocked Catalytic Converter – I don’t think that this your trouble, but Knowledge is Power etc.
If you move the plug to a different cylinder does the trouble ‘follow the plug’ or stay with the same #7 cylinder???
If the trouble stays with #7 regardless of which plug you swap – and I’m assuming its Coil on Plug – what is the pull down current on the #7 COP, is it enough to fire the coil/plug for #7 ?????
You say that you cleaned the MAF with ‘contact cleaner’. I’m unsure of what that is, but regardless, did you check the MAF before you cleaned it and again after. The ‘crime site’ of any fault can give you as much information before you touch anything as after you have done something. It’s too late now to take measurements of before but it should be reporting within OEM parameters now that it has been cleaned.
A dirty MAF will show a voltage that can be different from the specified voltage – this could be the problem, remember I am talking generically here I don’t know what your vehile is but the effect is the same, an the effect of a dirty/missreporting MAF would give you the symptoms you decribe.Again speaking generically, the ‘chip?’ in your air cleaner could be an ambient temerature sensor – again there are tests that apply to this – I do say to you that BEFORE you do anything to it, to check out its current operating reporting against the specifications for your vehicle.
If you do find that it is the MAF and you correct this, remember that the Long Term Fuel Trims will take some time to adjust to the new imformation of the MAF. Add Long Term Fuel Trims to Short Term Fuel Trims for a total Fuel Trim figure before and after the engine settles down/warms to operating temperature.
Knowledge is Power and Power means Control.
Just a thought, take out the Air cleaner Filter Element – could it be possible that your Air cleaner is Blocked/Dirty and retricting air flow.
I have number of scopes – but one the first I bought was a Hantek 8 chanel Analoge – Analyzer. In part I bought it because there are good intruction materials on Utube and it was cheap for what it could do. But in mu opinion you need to team it up with the Amp clamp, form memory there are two amp clamps, you git the one that suits your needs.
hhttps://www.ebay.co.uk/itm/Handheld-Digital-Oscilloscope-Automotive-8-Channels-Analog-Analyzer-Logic-Bag/123818624022?_trkparms=ispr%3D1&hash=item1cd42a4416:g:teEAAOSwYu1coC1~&enc=AQAEAAACYBPxNw%2BVj6nta7CKEs3N0qVJhxXosS%2Fe2xn0C9nxG8jRhE3e14HYAr0iZV2AnEtJ5Lpe93yEfcTHuJ%2FI4PZxb6XhkbPn0aUHX3y3x1OUQXr6roXd2rXhAGLlaqtuhJWQ1XHl6rBKGEToqyN0ivk6VMuSyY3owHlAV2wZUlmt2aZOEoUwoi3KvXckr9S50IXSjPdDlpy8EhwVmVZXoq0ebPwXWW%2BwJWTiuY3sMn%2Ffhhm%2F7p0Dm5T4rdEO6YrWW6hq5GOrEJE%2BYFo3jwHqLlSPJQoL77LBCTIIgPw7a4QyzCNPpxjuw0lNvtcPLHJJmPKEB%2F20BS08VmUDIqblj8W%2FXv0QGAuCWQNB1BiI%2F1c%2B0UFNhLnx2IzSGx2uqXkt0AJrDhy8tXEGq1goknXbeD6XLxigfG6%2FsxN0qRgLl3funkusyCunmy7Dy8WirpbWwE%2F6zKFyhPVXw1XoujAwKldIZrP3J1nqHCwegB5RCN9w2vnW974ma2HPUnj4Lns6a6IwVhLujMt9LwsWU6bI%2BakthXLb7bHqgHGvJ%2B6tk4Kq56yDYUwVYppxc9GZnW5knCpotx7B6wU0n0RLGfz7fqz2FhgJaIBjjVSrquqKFaLrhjIuSoM1Dke2x3Q1F77nmalmrXUjG3GZj4HEegXngqTEaodg5F4dL6dYtoksA93ERMg7uqdg7dJhUz3OSkcInGXDmRQ7nEx9pubtyeN5QltzyAbeCYXI%2Fjuo07bUtAEDK%2FMu3mYPVTFVZyfvdnAt0UrZ1JyzRg%2BSSjPN9WSsDIwSJq5mer3PU%2FFR2tW3Hs0x8it1&checksum=123818624022a6f014e2e8bf4861ace4a7dff060c28dave
In my opinion, coil on plug is not a factor here. I can’t see that it would make any diference to this situation – the sugestion of looking at the sparklines on a scope is that they show the effect of leaner and / or richer cylinder mixtures.
There are on some vehicles diaphram type units that operate vacuum lines/sensors and if you have one of these (remember I am speaking genericaly) here as I don’t know what vehicle you have. If you have a leak in the diaphram it is possilbe for fuel to pass into vacuum lines and then to intake manifold and then to causing a type of problem you have described. You can ‘suck and see’ on these diaphram units and see if they are vacuum tight – I guess that you will not be able to suck and much as the intake manifold but it does not require a gauge to find a leaking diaphram.
As you don’t have a scope or fuel pressure gauge and I’m assuming the fuel pressure regulator is not adjustable you have reached a sticking point. Even if the fuel regulator is adjustable you would still need a fuel pressure gauge to set the regulator. One can set a fuel pressure regulator on a ‘suck and see’ basis but it requires practice and experience, something that comes with hair in the nose and ears.
There has been a fair bit of use of the “B” word here (buy), can you get access to a mechanic who comes with hair in his nose and ears and tell him what you have done and get a quote to either fix the problem or scope the vehicle and steer you onto the next course of action. Finding a good mechanic takes research and networking with people you come into contact with.
Don’t go into the first shop you see and say “fix this”. Spend as much time on the search for a good mechanic as you have spent so far on the vehicle. Knowledge is Power and Power means control and you need very much to stay in control of this situation, so develope the Knowledge to deal with the problem. If you find a good mechanic who will talk with you rather than too you, it would be a good step on the track to fixing this situation. You are already on this journey and you have found this website, good luck.
It would appear that the engine is rich which is shown by the negative fuel trims as the computer tries to correct and bring it back to a stiochiometric ratio. This is reinforced by the black ring of carbon on the plugs, the rough idle which is worse when hot, a cold motor running better when richer and worse when hot.
Look for causes of richness in the cylinders
You say that one bank is trying to compensate more than the other – this gives some direction as to the location. You’ve ordered a fuel pressure regulator, but what was the fuel pressure. It’s interesting to read that the extra time taken to let the fuel pump prime the rail has an effect on starting, this should get to pressure almost instantly, again what was the fuel pressure??? It seems condradictory that it takes longer to prime the rail and then when it does the engine is rich. Is the return to the tank restricted/ blocked causing the pump to fight the blockage and then the rail pressure is high because it can’t release the excess to the tank??? – thus causing a higher pressure to injectors leading to a rich condition in turn causing fuel trims to go lean to correct the situation. Remember that pressure of a fuel is not the same thing as delivery of a fuel.
I get the impression that you don’t have a scope – I would like to see the firing lines on the plugs to see whcih cylinders are richer and which are leaner.
If it was a horse you could shoot it, as it’s a car just keep on making the payments !!!
Sometimes the solution is so simple that it can be overlooked – you have not said that you moved the #2 spark plug to another location (cylinder) to see if the missfire moved right along with the plug. If you have not tried this, do so, the cost is zero. The plug is an intedgral part of the circuit and needs to be checked………….
Knowledge is power – power is controll. In essence, you must have the knowledge to be in controll of any situation. A thought: extemismn is always founded on ignorance.
