1 Cylinder No Spark

[paulh634]

Cylinder 2 has no spark, all other cylinders fully functional.

Narrowed down to wiring by testing with multiple coil packs/spark plugs grounding on intake manifold. All coils/plugs work on all other cylinders, however no spark on cylinder 2.

2nd Generation PTU, have verified via resistance testing in FSM that this PTU is within spec. From my readings I don't believe the PTU would cause a single cylinder to not spark, although I believe this testing should rule this out either way.

Tested connector to coil pack:
a has continuity to ground,
b has 12v,
c has continuity to PTU.
***(a,b,c referring to the labeling of coil connectors on diagrams located on EF&EC 119 of FSM)***

Cleaned all connectors to PTU and CAS, all seem to have no corrosion and be in good condition.

I do not have a way to measure pulse to the 3rd contact on the coil connector (contact c), I've gone through the troubleshooting on EF&EC 119 diagram d in the factory service manual and have continuity between connectors 1-6 on the PTU and their corresponding connections on the ECU (1-1, 2-2, 3-3, 4-11,5-12,6-13).

I'm assuming in step E that the pin 21 is the ground pin on the PTU connector (all the way to one side, next to white wire), and this does indeed have continuity to ground.

What am I missing here?

[ca18det_boy]

Hi Paul, welcome to NICO! I also would like to say thank you. It's not often that a post comes through with people doing some legwork and providing as much information as you have. It really helps out with the troubleshooting.

So I have a couple questions for you. Is the ECU throwing any codes? Have you swapped coils to see if the problem follows the coil? Is your injector on the cylinder working?

Typically the PTU either works or it doesn't. So it would be safe to assume that there isn't an issue there. However, an easy way to check it real time is to pull your CAS and manually turn it. That way you save the wear and tear on your starter/battery. Plus you don't need the additional set of hands to assist. Also doing that, you can check to see pulses from the PTU.

[paulh634]

ECU is throwing no codes, flashes 55, no faults.

I have swapped coils and plugs between cylinders to no avail. eg. Coil and plug from cylinder 2 work fine when connected to cylinder 3 coil connector.

Injectors and injector wiring were just replaced with new, verified via ohm testing and with stethoscope for proper function, however that would most likely be unrelated from my knowledge as I have visually verified no spark.

When manually turning the ptu I would measure the voltage from pin c on coil connector to ground while manually spinning the CAS? Or how exactly would I see the pulse?

Also thank you very much for your help!

[ca18det_boy]

Yes, you would see where the PTU sends the signal to the coil to fire with an ohm meter and measuring the pin. I'm not concerned with the injector wiring though. The reason I asked about the injectors is because the injectors gets the signal from the CAS. The CAS also sends the signal for the coil to fire. So currently my train of thought is check to see if that injector is firing. If the injector isn't firing on that cylinder, then I personally would start troubleshooting at the ECU to verify that it is sending out the correct signal. If the injector is firing, then now the problem is from the ECU to the coil. As luck would have it, the only thing (off the top of my head) between the ECU and coil is a ground and the PTU. Since you've already checked from the PTU to the coil, the only thing that is left is the wiring from the PTU to the ECU.

[paulh634]

So...

Just tested all injector connectors with a noid light and all of them including the dead cylinder are getting signal (noid light flashes). So I believe the CAS is working properly, however I'm not positive that this confirms this.

I have tested from the PTU to the ECU per the procedure in my first post. Is there another way to test this, or did I do that correctly?

I tried to connect the noid light between the signal wire and the ground on the coil connector, however it did not flash on any of the cylinders, so I don't think this is a valid test.

I'm not exactly following measuring the voltage of the pin with dmm, I think I'm missing something reading through your last post.
Also if the CAS is removed does timing need to be readjusted?

[ca18det_boy]

If you remove the CAS then yes, you'll have to reset your timing. It just makes it easier to troubleshoot and it saves the wear and tear on your starter/battery. I thought in your first post you meant you checked wiring from PTU to coil, not PTU to ECU. If I misunderstood I'm sorry.

Ok, so back to troubleshooting...So you're getting a pulse from the injectors, that's good and means that the CAS should be working correctly. For the coil connector, I'm more of a DMM guy instead of light due to the fact that I haven't had the best of luck using them. I get better results with the DMM. You're on to way I'm saying though, I would check it at the signal wire and record voltage (if any).

If you're still not having any luck there, then it would appear that your issue is between the PTU and the ECU. Can you re-verify grounds at on the ECU at pins 10 and 20, then you can check pin 2 for voltage while cranking/turning the CAS. After you do that I would verify continuity between pin 2 up to the PTU.

Can we get some background information on the car? Did you just get it? Was any maintenance done just prior to the issue? Was there any extenuating circumstances that happened just prior to the issue? Or did you just get up one day and it wasn't firing on cylinder 2?

[paulh634]

No worries, I just wanted to make sure we were on the same page with the ptu to ecu deal.

I tried measuring voltage at the signal wire. Looking at the wiring diagram it seems that it should pulse between 2 and 5 volts if I'm not mistaken. However I get 0 on all cylinders, working or not. So that leaves me a little confused.

I did not check pins 10 or 20. I will check those as soon as I can. (might be this weekend, I'm in southern AZ so the garage is a furnace by the time I get off work in the evening

I got the car after someone had changed fuel injectors and fuel rail to use the TT injectors. Was running on 2 cylinders when I got it. Multiple injectors had failed and the ptu harness had some corrosion. Replaced fuel rail and injectors with stock and replaced all of the injector wiring. That fixed all but the one cylinder. I got another ptu that I'm going to swap in and see if that fixes the issue.

Thank you again!

[ca18det_boy]

I'm in NW Phoenix, so I totally get what you're saying about the heat. I often procrastinate on going out to the garage, but more often than not I just make myself do it and regret it later.

That's odd that you're not getting any voltage, were you cranking or having someone turn the CAS while you were measuring? If you have a buddy down there that has a spare ECU it wouldn't hurt to go ahead and see if that one does anything different.

[paulh634]

Replaced PTU and rewired all of the coil connectors. This has solved the issue on cylinder 2, however cylinder 5 has no spark. Going to start at square one and retrace my steps. Hopefully I'm just overlooking something simple on this.

I'm having issues with the idle hunting. It hovers around 2,000 rpm and then will jump between 2,000 and 2,300 every couple seconds. Going to check for intake leaks as I just had the intake and vacuum lines off.

Thank you again for your help.

[paulh634]

Wiring on cylinder 5 was not making a good connection, rewired and all cylinders are firing.

However I still have the issue with the idle hunting. (vroom vroom vroom vroom).
I tested the pressure in the vacuum lines and I'm getting about 15 around 2000 rpm. So perhaps a little low, but I don't think that indicates a leak as it would be close to 0. Any advice on why this might be happening?

Perhaps this should be a new post.

[paulh634]

Running 100%

After hunting for vacuum leaks for hours it turns out that if the throttle cable is too tight the idle will be high and bounce.

Thank you very much ca18det_boy, next time I'm in Phoenix I definitely owe you a beer or two!!

[ca18det_boy]

Dude I'm glad that everything worked out!! So how's it run going down the road?

Also, just to satisfy my curiosity...would you please swap back PTU's so that way we know if it was the wiring or if it was the PTU that was causing the issue? I'd bet on wiring, but it would be nice just to know for sure. Thanks man!!

[paulh634]

Swapped back PTU and I don't think there is a difference. I haven't ran it long with the old now that everything is fixed, but i'm guessing it was wiring. Everything seems to be good!!