I also want to add, this is 100% a fuel issue, spark has been verified and is fine on all cylinders.

 

Inj harness is backwards....

1872
_______
6543

 

Hmm, for the swap I depinned the whole harness to lay things out better to relocate the pcm. I have verified and double/ triple checked that all of the injector signal wires are pinned to the pcm properly and in the correct order/ location. There isn't really any injector harness to speak of, just 1 wire form each to ignition 12v source, and the other wire straight to the pcm.

 

I have it pinned that injector signal 1 is pin 36 and a black wire
Inj 2= pin 4. green/ black wire
Inj 3= pin 3, pink/black wire
Inj 4= pin 44, blue/ black
Inj 5= pin 76, black/ white
Inj 6= pin 37, yellow/ black
Inj 7= pin 43, red/ black
Inj 8= pin 77, blue/ white.

You do no have me really thinking about the fact that it's literally the second half of the firing order thats missing and what that could mean.

 

if you 100% have spark on all 8 cylinders AND at the correct time for each cylinder, then that would heavily point towards an injector wiring issue.

If there were also spark problems, it could be a crank/cam trigger issue

Injector wiring is simple. They need 12v, that applies to all. Then 1 wire to the relevant ecu output for each injector. Has this been confirmed ?

 

Yes I have double and tripled checked that each injector wire is to the correct pcm pin, and each wire has continuity. Each injector does have a good 12v source. For troubleshooting I have even redone and made a dead simple power supply to the problem cylinders so power is not an issue.

I think the injector wiring portion is okay. For troubleshooting I unplugged the pcm, put key on to supply 12v and using a power probe, I supplied ground to the pins for each injector 1 at a time and I could hear each one click. That tells me that the wiring on the control side is fine as well.

What throws me off is that with the engine cranking, I can use both the power probe or multimeter and pick up a pulsed ground signal directly at the injector plug which tells me that it SHOULD fire, but doesn't. Or at least isn't adding fuel, or not at the correct time. The spark plugs from these cylinders look perfectly clean.

 

I just went back to square 1 for diagnoses. I put the super rich (essentially doubled VE table back in it just so it will run), and put the timing light on every cylinder, great spark everywhere. I pulled the valve covers and double checked the valvetrain, all is well there.

All signs still point to fuel, but every damn thing I check in the fuel injectors and system checks out perfectly fine. I'm lost.

 

The time in the cycle for a sequential car wouldnt be overly important for the purposes of this problem.

You seem to be saying during cranking, all 8 injectors are actually receiving a valid signal ? And they do have 12v during this time too ?

If so, they can do nothing else but fire. Measure the pulse width they are receiving either with a multimeter or scope.

Is the problem then that once running this is not maintained ? Or are you saying no fuel is being injected during cranking ?

 

You seem to be saying during cranking, all 8 injectors are actually receiving a valid signal ? And they do have 12v during this time too ?
-Correct
Is the problem then that once running this is not maintained ? Or are you saying no fuel is being injected during cranking ?

It fires up well, mostly because I have the cranking VE table really rich for now, but I dont believe they fire at all, cranking or running. The plugs come out clean as can be.

 

And has this ecu/wiring/setup ever ran correctly ?

Or is every aspect an unknown ?

 

https://www.facebook.com/steve.sutherland.5/videos/10154600499785685/

Here is what it's doing. Power while running is good, pulsed ground is good, same on all cylinders. However the same cylinders are still not firing, I can actually unplug them with no change except for the 4 keeping the motor going.

We even then tried swapping the injector plug between cylinders 1 and 3, and then repinning the other end at the pcm and tried it again, and even then 1 continued to work perfectly and 3 does not fire.

I tried manually applying ground to the injector control wire with the motor running and the injector very clearly worked, motor sound changed the AFR went way rich on the wideband, so the injectors have fuel and can fire, they just simply don't.

With the engine off, we backprobed all the connectors and there is continuity so the connection between the plug and the injectors are also good.

This tune is from the sloppy mechanics page, and I have confirmed with a few other guys who have run it without issue. We also tried a second pcm for trouble shooting with absolutely no change.

 

I know you're testing between 12v and inj trigger...

But what happens when you test between both wires of the actual injector ? Ideally when the injector is still plugged in.

The engine is clearly running there...and for only being on 4 cylinders, sounds incredibly well on the video ?

What fault codes are showing ? There must be some sort of codes or warnings that the ecu is not happy.

Lambda readings must be extremely odd too ?

What happens if you swap a "dead wiring" cylinder, say 5...to cylinder 7 ? and visa versa ?

7 should now become dead and 5 live ?

Exactly how are you determining the dead cylinders ? Just by sound ? Can you IR gun those exhaust ports to see if they are firing ?

Do your fuel rails unbolt easily, and have injector retaining clips ? ie could you lift the rails/injectors away from the manifold and get a visual of whether anything at all is being injected ?

 

The stock computer will run low impedance injectors?

 

It may..........For a while. Then, the drivers will over heat, and burn out.

 

he hasnt stated he is using low impedance ?

 

I was responding to T Fiddler's post.

 

Hey guys sorry it took me so long to get back to this. I have the high impedence version of the injectors because I was concerned about that for obvious reasons haha.
I borrowed an IR temp gun and that confirmed that the cylinders in question arent firing.
I tried swapping wiring in2 ways. One, I used the injector 1 wire/plug on cylinder 3, and vice versa- I then changed the firing order on HP tuners and it made no difference. I did the same thing with the coil plugs for those same cylinders, and then crossed the plug wires. Essentially so that all the cylinder 1 wires/coil and plug wire that worked on #1, was firing 3, but still #3 was dead.

I am getting so angry at this.. Lol. I know it has to be some very stupid issue, that I can wait to find and feel dumb.

 

If you have changed everything, so without question there is both fuel and spark available at cylinder 3 and it still isnt firing, then you need to start looking at mechanical issues.

 

I tend to agree with you. I have checked the compression on cylinders 1 and 3 and saw 175-180 on both. I didn't bother to check the rest because #3 is one of the trouble cylinders and with great compression on it compared to a good cylinder I don't think that is an issue. I have pulled the valve covers and cranked the motor over and watched all of the rockers operate properly. I have also swapped plugs to an new set, and swapped between cylinders. I have also pulled the intake and verified there is no obstruction or obvious issues in the runners.

 

Just curious if you've tried swapping in a known good ECU? I don't recall reading if you've tried that or not.

Or maybe some electromagnetic interference going on?

When you find out what's wrong PLEASE let us know! This sounds like one nasty problem! I feel for you man! Good luck.

 

Yeah in the shop there is another project truck with a 2001 P01 dbc pcm that I needed to license and tune anyways, so I borrowed it and tried it, with identical results.

That's interesting about possible interference, I have the wires all run together through the firewall towards the glovebox, there really isn't anything else in the area but I suppose its possible.

I have had a lot of people looking at the car trying to figure it out, plus the forums and there seems to be a lot of people that are anxious to see what this problem could be. Once I get it I will absolutely post it up in case some one else ends up in the same situation. I'm already blazing the path up shit creek so I may as well put up signs for whoever follows me haha.

 

Your most recent post seemed to imply only cylinder 3 was down. So is it only cyl 3, or is it still the same 4 cylinders ?

Have you confirmed crank and cam triggers are all good ?

 

-It is all 4 middle cylinders (3,5,4,6), I was just testing specifically with 1 and 3 to help narrow things down quicker.
- I have swapped the cam and crank sensors with no change.

Update: I worked on the car again today and got more details. I finalized the exhaust and wideband 02 and was using Hp tuners to disable injectors one at a time. All of the injectors ARE firing, but there's something significantly different between 1,2,7,8 and 3,4,5,6 as I ave known and been working on. I pulled the intake and cranked it and physically saw that the injectors are all firing, seeming equally (at least during cranking).

So I used HP tuners to disable 1 injector at a time. It's a little confusing because the injector number don't seem to correlate perfectly to the cylinder #'s, so think they go by firing order. Anyways, the motor idles steady at 13.9-14.1 AFR, and disabling any one of injectors 1-4 results in the motor leaning out to ~15.1 AFR. Whereas if I disable injectors 5-8 then the motor falls on it's face, AFR goes lean above 18.0 (off the wideband) and there is an immediate and audible misfire.

I took that to mean that the injectors and fuel was fine, so I started re-checking spark. From the coil there is a strong, evenly timed spark from each one of the 8 coils, and I have swapped coils, plug and wire that I know to be good with no change.

Seeing that the spark is great, and I know cranking compression is 175-180 across the board, I am leaning back towards fuel as the cause, but am completely stumped still.

 

So I used HP tuners to disable 1 injector at a time. It's a little confusing because the injector number don't seem to correlate perfectly to the cylinder #'s, so think they go by firing order.

Can someone verify this. Seems odd.

 

" All of the injectors ARE firing, but there's something significantly different between 1,2,7,8 and 3,4,5,6 as I ave known and been working on"

Refer to post # 3.....

 

There is no injector harness to have backwards, they are 8 individual power wires, and 8 individual ground wires from the pcm. The injector leads from the pcm have been checked, and rechecked by a number of people. If you care to explain more how you think the "injector harness" is backward or would explain what you can see in the video I would be happy to hear it though.

 

To help simplify things, here is a quick video I took today showing the motors response to pulling injector plugs and how #3 only changes AFR by 1 point, but unplugging #1 drops it by over 4 points of AFR. It also shows the spark on a couple of the cylinders and comparing a good cylinder to a bad one (both have the same, good spark). Ignore my extra red wires, the multimeter showed I had good ground on the coil bank, but to be extra safe I added a whole bunch of extra super quick grounds just to be damn sure and just tightened them under the coil mount bolts.

https://www.facebook.com/steve.suth...685/?hc_ref=ARQey4ug8gS53CAh4EFB70Vs0INTlF_uf9ByJw7GVoE5yAoH67e6sGzrNXC0r-JgHxc

 

Reposting the video with a link where the video is public.
https://www.facebook.com/steve.sutherland.5/videos/10154631277180685/

 

Not really sure whether to say what you did in the video was very brave, or very stupid !!

The test is valid, but pulling HT leads off a coil like that with your bare hands and the engine running on a car with such a power ignition system, is a little crazy.

It does seem clear you have some degree of fuel and spark available at the relevant cylinders. Most likely it is not at the correct time though.

I did also say to test crank/cam triggers, swapping sensors is not a full and conclusive test....although I'd think if the cam trigger was not good, the ecu would be reporting this given it most likely has a good crank trigger otherwise it wouldnt run at all.

The mismatch is a little odd.....try swapping coil wires between 3/5 and 4/6. They are beside each other that should be easy ( and also try injector wires too in a similar manner )

 

That's true, that would narrow it down right away, I will try that just for reference.

The thought I have in the back of my mind now is if I have messed up the pins at the pcm for ignition control for those cylinders. Since I have fuel, and spark, a few people have mentioned that maybe it is the timing of those events. I had rechecked the injector wires from the pcm and found they were all right, and because the coils have their own subharness that I never touched, I discounted that. However I could have definitely made a mistake and swapped these when repinning the pcm when I reworked the harness.

If I'm right, those particular cylinders would all be firing quite late, which makes sense why it only backfires in the exhaust and not the intake. As much as I would hate to have made a stupid mistake like that, I would love for the fix to be this simple. I am going to work on it tomorrow and will keep you posted one way or another.