Need help diagnoising Misfire.

[JDMMA70]

So my rebuilt engine is running great a compression test this morning showed great results. Anyways its got this annoying misfire that I finally decided to at around 300miles to pull the spark plugs and see what the deal is. All the plugs except #4 looked good. #4 looks like its running rich maybe? Plugs look black. It definitely seems like it would cause my misfire. Its noticeable at idle and at above 1000rpms to 3000rpms after that it gets hard to notice. Compression on that cylinder was 175psi. I put in a new plug and drove it for another 150miles pulled the plug again and examined. Repeated again this time even shorter to see how fast its fouling. Pulled this most recent one at 540miles. I checked the injector resistance its within spec. I checked the pulse/sound of the injectors and compared with the others it all sounds the same. Ignition timing is set to 10' BTDC. Spark plugs are BCPR7ES Coppers. The only thing that could possibly affect fueling is a crack well cracks on my accordion hose where it meets the turbo. However that doesn't explain why its only affecting one cylinder. I know the cracks aren't helping and a new hose is on order from Toyota, I'm not sure what else it could be. Vacuum gauge reading at idle is about 21inHg. Vacuum on hard deceleration it pulls around 26-28inHG, so it would seem all is mechanically fine (block and head wise). BVSV is broken (ordered a new one) so Ive bypassed it for now. Checked the coils, and power to the coil harness as well as the Ignitor and all of those check out. CPS is brand new.

Here are pics of the plugs.

Plug #1 (300miles)



Plug #2 (150miles)



Plug #3 (100miles)



Thanks
~JDMMA70

 

[Poodles]

That's what any plug that's misfiring looks like...

If it was all of the plugs, I'd say they're too cold. Generally speaking though, if you replace plugs and you still get the misfire, you check the rest of the ignition system. If all the parts there check out, then fuel system. If that checks out, then mechanical condition with the engine.

As we have a wasted spark setup, and you don't have any issues with the corresponding cylinder, I'd be looking at the wire...

 

[JDMMA70]

The wires checked out even tested with a spare ngk and oem set. Misfire persists. Swapped coils around just for kicks. I'm pulling the injectors off to be tested and cleaned may as well and it certainly wouldn't hurt.

 

[JDMMA70]

Had the injectors cleaned still has a misfire. I checked to see if the intake valve seals were lealing any oil down the valves. I saw none via inspection camera. Dunno about the exhaust side. As I mentioned though head was rebuilt. I'm out of ideas any suggestions on where to start next?

Also I have noticed it only "seems" to misfire in closed loop

 

[hvyman]

Try a leak down test.

 

[JDMMA70]

I need to buy a tester and a air compressor. So looks like for now it will have to wait until I get one. So really a leak down test pretty much is going to be the only thing to do at this point. Man I'm going to be so pissed if something is wonky with the head.

 

[jetjock]

Secondary waveform analysis...

 

[7M-KDL]

JJ. if he doesn't have a leakdown tester and air compressor I doubt he's got a scope. However, if he can find one that will definitely show his trouble area. I would recommend doing an injector balance test unless the shop that cleaned them was able to properly bench test them. I am curious as to whether the misfire is actually "closed loop" realated or just heat related. Did you check the resistance of the injectors hot or cold? How well do the wires connect, do you hear them click in place? Notice any arcing or orange deposits around either end of the plug wire? Also, it could go either way, running rich causing the plugs to be wet and not fire or not firing causing fuel to just sit on them, without secondary ignition waveforms it's hard to tell. Did you mark the injectors when you removed them and put them all back in the same place after cleaning?

 

[JDMMA70]

JJ. if he doesn't have a leakdown tester and air compressor I doubt he's got a scope. However, if he can find one that will definitely show his trouble area. I would recommend doing an injector balance test unless the shop that cleaned them was able to properly bench test them. I am curious as to whether the misfire is actually "closed loop" realated or just heat related. Did you check the resistance of the injectors hot or cold? How well do the wires connect, do you hear them click in place? Notice any arcing or orange deposits around either end of the plug wire? Also, it could go either way, running rich causing the plugs to be wet and not fire or not firing causing fuel to just sit on them, without secondary ignition waveforms it's hard to tell. Did you mark the injectors when you removed them and put them all back in the same place after cleaning?

The injectors after a ultrasonic cleaning all flow 456cc. I did put them all back in the same place except cylinder my problem cylinder. I moved that injector to cylinde #1. My plugs are in bad shape as most are from a harness this old. They are tightly on though. I checked the resistance cold well semi warm 3.3ohms iirc. I'm pulling my plugs again for inspection.

 

[JDMMA70]

So im starting to think it may be my valve stem seals (dunno how brand new seals could fail so early.) I recorded three videos one of start up, one outside to show the misfire, and then of my oil pressure cruising.

Im wondering if I need an oil restrictor on my GReddy TD06-20G or it has one built in already. However seeing my spark plugs it may be likely that its the seals on that cylinder hopefully that rather than the guides. However the head was rebuilt so im keeping my fingers crossed the machine shop did what they said they did. However can bad seals cause a misfire like this? I ask because my old motor had leaking seals on all six cylinders, and never misfired like this. Also the car has become harder to start since the motor went in.

 

[7M-KDL]

I have had/seen many cars with leaking valve seals and no misfire. I doubt that an oil leak is causing the misfire unless it is just pouring it in and filling the cylinder. I didn't see enough smoke from the exhaust to prove that though. To be clear, I'm not saying the seals aren't a problem but I doubt they misfire related.Worn guides or a weak or broken valve spring could cause it if they are not seating the valves properly . Did you have a chance to get a leak down tester yet? Have you tried the paper test(hold a 3x5 card at the exhaust tip and see if its constantly puffing out or if it is sucked back toward the pipe when the miss occurs)? Did the plugs smell like gas or are they oily?

 

[JDMMA70]

I haven't gotten a tester yet. Ill try the paper test. The plugs except on #4 are fine. #4 is dry by the time I pull it but its just black. Doesn't look wet or an oily wet. Its dry and it does rub off doesn't smell like gas or oil. I did crank the car with no plugs and gas sprayed out of the cylinder. When I look in with a camera it looks like oil is resting on the pistons. When I was burping the cooling system today I.noticed the misfire didn't start until it went into closed loop. My finger was on the throttle holding at 1500 went into closed loop rpms dropped sharply and started missing. O2 sensor maybe? That doesn't explain why only one cylinder is off.

 

[7M-KDL]

Yeh, o2 can cause problems but typically not on one cylinder, a simple test for that would be to unplug it and see if the car still misfires. That may help determine whether it is actually "closed loop" related or time/temperature related.

 

[JDMMA70]

Is there anything else that could cause a one cylinder issue that I could check? I'm out of ideas right now.

 

[7M-KDL]

Do you have a spark tester? What coil setup are your running? Have you done the igniter ground mod? Try spraying the wires with the car running with a mix of water/alcohol and look for arcing or see if the miss gets worse. Another thing would be to take a stethoscope and listen to the injectors, make sure they all sound the same.

 

[JDMMA70]

Do you have a spark tester? What coil setup are your running? Have you done the igniter ground mod? Try spraying the wires with the car running with a mix of water/alcohol and look for arcing or see if the miss gets worse. Another thing would be to take a stethoscope and listen to the injectors, make sure they all sound the same.

Stock coils. I used a screwdriver to listen to the injectors they all sounded the same. I've done the ignitor ground mod. I done have a spark tester. I do have pictures of inside the cylinder ill upload when I get off work. Ill try the spray.

 

[JDMMA70]

Ok Im too tired to do any of the testing tonight, I will post tomorrow with my findings. Here are the picture of inside Cylinder 4 and its neighbor Cylinder 3. Just like the spark plugs only Cylinder 4 looks like that all the others have a nice tan colour on the pistons.

Cylinder 4



Cylinder 3

 

[7M-KDL]

Both pistons look like they have oil on top of them. Try running the car to get rid of the oil, pull the plug and inspect, if there is no oil on top then manually set the number 4 cylinder to TDC and let it sit overnight(or several hours). Check it again in the morning, if there is oil on the top(assuming there wasn't any the night before) then you have a leaking valve. Hopefully that makes sense.

 

[JDMMA70]

Its not oil confirmed it this morning. Its fuel on top of cylinder 4 piston. I'm checking the injector wiring.

 

[7M-KDL]

Glad you're making progress. Sounds like you are at injector wiring or driver now since you've swapped injectors already. Good luck.