1G Potential Stuck Open Injector

[sebas-1024]

Hello, back again with trouble on my '92 Galant.

A couple of weeks ago the car developed a misfire in cylinder 2. I had them serviced along with the spark plugs (they cleaned them up with a brush and a pick, nothing fancy) and the car idled as before, but a couple of days ago the misfire on cylinder 2 returned.

I thought it was clogged or something again, but I noticed a lot of smoke coming from the exhaust, so there was fuel being injected, it jut wasn't being burnt. I pull out spark plugs and the one from cylinder 2 is pitch black (Image 1) while the others looked ok (Image 2). I swapped that one with an old one that was laying around in the car and it seems to be working well enough again, but I'm pretty sure that the main issue is that the Cylinder 2 injector is stuck open and I'll have a misfire in a few days again once the "new" spark plug gets drenched.

Do I need to check anything else or is it certain that the injector is the issue here? And if so, where I can get a set of reliable and if possible cheap stock injectors. It's a '92 Galant with a naturally aspirated 4g63, FWD and an automatic transmission.

Thanks in advance for any help!

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Image 1 - Spark Plug from Cylinder 2 covered in what I believe to be fuel.

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Image 2 - Spark Plug from Cylinder 1 (the rest looked like this one)

 

[dwb]

How are your spark plug wires? Is it possible #2 is grounding out/arcing before the spark plug?

You could also swap injectors around to see if the problem moves to a different cylinder.

 

[sebas-1024]

How are your spark plug wires? Is it possible #2 is grounding out/arcing before the spark plug?

You could also swap injectors around to see if the problem moves to a different cylinder.

I tested for spark before changing the spark plugs, all of the coils are working well, changing the injectors is a good idea though, I'll try that as well. Thanks!

 

[steve]

Be prepaired to replace the injector insulators that sit between the head and injector when you swap injectors. The existing ones are likely hard and won't seal after. Good time to replace the o-rings as well and lube the new ones before installing the injectors back in the fuel rail.

 

[sebas-1024]

How are your spark plug wires? Is it possible #2 is grounding out/arcing before the spark plug?

You could also swap injectors around to see if the problem moves to a different cylinder.

Swapped injectors 1 and 2, will check which spark plug goes black when the misfire comes back.

 

[sebas-1024]

Be prepaired to replace the injector insulators that sit between the head and injector when you swap injectors. The existing ones are likely hard and won't seal after. Good time to replace the o-rings as well and lube the new ones before installing the injectors back in the fuel rail.

No idea about what those are, when I took them to be serviced they replaced 3 "rubber elements" (Not sure if they were all o-rings or insulators as you say), is there a diagram in the manual for all that it should it should come with? Also, where can I find a good set of stock injectors? Nothing fancy just the most reliable for the best price.

 

[steve]

No idea about what those are?

I don't have a picture of them on a NA injector, these are on stock 450cc injectors. Yours go on the same but the injectors are a different color.

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[sebas-1024]

I don't have a picture of them on a NA injector, these are on stock 450cc injectors. Yours go on the same but the injectors are a different color.

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Thanks for that, the sheet, insulator and O-ring were all replaced when servicing them, but 2 of the injectors don't have this black element that I'm circling in red, it's just bare metal. I'm guessing that's also important, is it replaceable?

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Swapped injectors 1 and 2, will check which spark plug goes black when the misfire comes back.

Interestingly enough, the misfire came back and the same spark plug came out black, that is, the misfire did not move along with the injector, when the misfire is present there is definitely a strong fuel smell coming from the exhaust, along with smoke, so there is fuel being injected that is not being burned.

At this point I'm thinking it might be an ignition coil issue, that the spark is not strong enough and it burns progressively less fuel until the spark plug it's covered in it and won't ignite at all, if that makes any sense.

I just changed my old ECU for a "new" one, so I highly doubt that it is an ECU problem at this point. Any thoughts?

 

[steve]

2 of the injectors don't have this black element that I'm circling in red, it's just bare metal. I'm guessing that's also important, is it replaceable?

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That's the pintle cap. It does help seal the injector and helps the spray pattern. Good injector shops should have replacements. The 2G injectors have a different cap that actually forms two fuel jets from pintle outlet which Mitsubishi claims improved economy and emissions, so it does make a difference.

If they were missing, when did they go? Did the engine eat them?

I read too many threads to keep everything straight, have you done a compression and leakdown test of all the cylinders?

 

[aba-cadabba]

Does your fuel pressure regulator drop to zero when you shut the car off? I feel like I have a stuck open injector on one of my cars. My issue is that it starts really hard when it is warm, and the #1 plug is black with dry soot. slight misfires when it warm starts also but eventually clears up during the drive.

 

[CKOPOCT]

When you checked for spark I assume it was just a visual test, that plug 2 emitted a spark you could see. It is possible that the spark is present but weak, that some of the energy is being bled off through a partial grounding, or the energy produced is not at the level it should be. A weak spark can be blown out before the air/fuel mixture is fully ignited.

Consider checking the spark again and compare the color and duration across all of the cylinders. Also consider looking at the #2 plug wire to see if a part of the wire has a grayish ashy look as this is an indication that the wire is cross bleeding some of the spark to another wire or to a ground point.

 

[sebas-1024]

That's the pintle cap. It does help seal the injector and helps the spray pattern. Good injector shops should have replacements. The 2G injectors have a different cap that actually forms two fuel jets from pintle outlet which Mitsubishi claims improved economy and emissions, so it does make a difference.

If they were missing, when did they go? Did the engine eat them?

I read too many threads to keep everything straight, have you done a compression and leakdown test of all the cylinders?

No idea about where the pintle caps are or how they fell off, might have been missing for 20 years to be honest, I've had the car for about 3 years so I'm still finding new things about it, I know they should be replaced now.

Have not done a compresion and leakdown test of the cylinders, don't have the equipment.

I think I might have found the cause of the problem, I was checking everything and the spark plugs were good (before getting full of fuel), the wires don't look bad at all either (both spark plugs and cables are NGK and are only a few months old), thought to check the Ignition Coils since I was running out of options and I found that the "high voltage terminals" were very corroded (Images 1 and 2) so I cleaned them, reinstalled them, and replaced the spark plug that was not sparking anymore. I guess there was a very weak spark in cylinder 2 so it caused all of this, hope I'm not mistaken.

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Images 1& 2 - Corroded Ignition Coils

That was 3 days ago, and so far the car has been working with no misfires, I'll be sure that it was the cause if the misfire doesn't come back.

 

[sebas-1024]

Does your fuel pressure regulator drop to zero when you shut the car off? I feel like I have a stuck open injector on one of my cars. My issue is that it starts really hard when it is warm, and the #1 plug is black with dry soot. slight misfires when it warm starts also but eventually clears up during the drive.

Don't really know how to check that, but I think my issue was spark at the end in any case.

 

[sebas-1024]

When you checked for spark I assume it was just a visual test, that plug 2 emitted a spark you could see. It is possible that the spark is present but weak, that some of the energy is being bled off through a partial grounding, or the energy produced is not at the level it should be. A weak spark can be blown out before the air/fuel mixture is fully ignited.

Consider checking the spark again and compare the color and duration across all of the cylinders. Also consider looking at the #2 plug wire to see if a part of the wire has a grayish ashy look as this is an indication that the wire is cross bleeding some of the spark to another wire or to a ground point.

I think you were right with this as I explained in a previous comment, hope the problem is fixed. Thanks!

 

[CKOPOCT]

Excellent. Very glad you found the problem. Yes, the corrosion would definitely inhibit the spark voltage. Nice find.

 

[sebas-1024]

Excellent. Very glad you found the problem. Yes, the corrosion would definitely inhibit the spark voltage. Nice find.

I would think so too, but unfortunately the misfire came back today, so I haven't solved the problem.

After a few days, I started to feel that there was a rough idle (rougher than usual, the car is far from being in perfect shape), so I assumed the misfire was back and started checking the following:

1.When I cleaned the ignition coil to get rid of the corrosion a few days ago, I decided to swap spark plug wires 2 and 3, at the ignition coil, if now cylinder 3 stopped working, I could be sure that it was that specific port of the ignition coil (which is weird as I understand that ignition coil issues tend to happen in pairs for these cars).

2. I checked spark plugs 2 and 3 (those were replaced for new ones a few days ago when I thought the issue had been taken care of) expecting to find spark plug 3 full of fuel, it was not the case, or not yet at least, and the same for spark plug 2. They look well enough, though maybe a bit too dark for just a few days of light driving.

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Images 1 & 2 - Spark Plugs 3 and 2 (In that order)

3. I moved on to check for spark with a spark plug tester between the spark plug wire and the spark plug, they all seem to be sparking with the same intensity and frequency as far as I can tell, so maybe I do have decent enough spark. Tried attaching videos of the tests but it doesn't seem to be working.

4. I decided to just start the car and disconnect each injector to check for an idle drop, I was then surprised to see that Cylinder #1 is the one that isn't firing now, check that spark plug and it does seem to be fouled.

5. I have a few hypothesis but I'm not sure on how to proceed with the diagnosis, let me know what you think of the following:
a. Ignition Coil is bad and needs to be replaced: weird that it's intermittent and it moves from one cylinder to the other, but could explain a weak spark.
b. Ignition Module or its connections are bad: Image 3 shows that the connection is not exactly factory. I'm not sure how the module works but I'm assuming that it would be more likely to cause an intermittent misfire like the one I'm experiencing than something simpler like spark plugs or a stuck injector.

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Image 3 - Ignition Module connector full of "sillicone?"

c. A sensor somewhere is telling the ECU to inject too much fuel and it's causing it to run too rich, fouling the spark plugs in the process, I do sense a fuel smell even when the car is not misfiring, but weak spark would also cause that smell. Not sure what to look at though, do '92 Galants have O2 sensors for example?

As always, sorry for the long post and any help is appreciated.

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[sebas-1024]

Can't post the 4th video for some reason, maybe I was spamming too much, sorry for that.

 

[trogador2005]

Did you ever get this resolved?

 

[sebas-1024]

Did you ever get this resolved?

Not yet, so far I've just been replacing the spark plug when it gets fouled but that's not a solution of course. I'm thinking it's the Fuel Pressure Regulator, low compression, or the ignition timing needs to be properly adjusted; maybe even a combination of all 3, I just don't have the tools to check that right now, might need to find a decent mechanic for it.

 

[trogador2005]

Dang ok. We're having a similar problem. Hoping to get it sorted out this weekend. I'll let you know if we find something.