FJ62 3FE Cylinder 1 Not-Firing? Running Rich? (1 Viewer)

[vankho]

This pass weekend, I was doing some compression tests trying to diagnose a possible head gasket leak and did a double-take on the state of my relatively new spark plugs. FJ62 is pretty rough from a cold start, especially under 1500 RPM. There's an occasional popping sound but disappears as it warms up. I suspect it is running rich.

Spark plugs are shown below in reverse order (6-5-4-3-2-1) As you can see in the image, spark plugs seem heavily covered in carbon, especially spark plug 5 and 3. Spark plug 1 however is very clean. I've turned my attention to investigating spark plug 1. I'm also running down the FSM troubleshoot steps for Misfires and Running rich condition. Below are some of the things I've done to troubleshoot and would appreciate any insight or wisdom you guys might have before I end up unnecessarily taking apart the the engine to check injectors and valves, buying new parts, or taking it into the shop.

Misfire Test
I was able to confirm that there was an issue with cylinder 1 by disconnecting the spark plug cable while the engine was running and not hearing any change in idle RPM. Other cylinders saw a notable audible drop in RPM when disconnected.

Swapped Spark Plugs
I've swapped spark plugs 1 and 2 and saw no change in cylinder 1 performance.

Spark Test
I removed spark plug 1 and attached it to the end of the spark cable, grounded it, and ran the engine and I think I was able to get spark on recording. Not sure if it's a good spark or weak spark though. Apologies for the shaky footage as I had to rest the camera on some hoses in the engine bay.

Engine Vacuum
Vacuum is holding at a steady at 21 inHg

Diagnostics Codes
System did not return codes this time around, but in the past I have gotten Code 11 and Code 51.

Ignition Timing
Recently adjusted the timing a few months ago to standard 7º BDTC at idle.

Cold Start Injector
Resistance measured at 3.2 Ω. Within range of specified 2-4 Ω.
Did not measure cold start injector time switch

Fuel Pressure
Did not measure as I do not have gauges.
Did not check fuel pressure regulator.


Injectors
Did not perform sound scope test as I did not have the tool.
Resistance for injector 1 measured at 13.9Ω. Within spec of 13.8Ω.

Spark Plugs
Did not measure gap as they are 2 months old.

Compression Test

1. 142
2. 135
3. 137
4. 130
5. 135
6. 134

Valve Clearance
Did not measure

EFI Electronic Circuit Check
Have not checked yet, but plan to.

Spark Cord w/ Distributor Cap Resistance

1. 6.61
2. 5.03
3. 3.73
4. 3.33
5. 5.03
6. 6.42

Ignition Coil Resistance Check
Primary coil is .6Ω
Secondary coil is 12.85 kΩ


I'm turning my attention towards it being something EFI related, but just not certain which part or component. I did noticed that the clip on Fuel Injector 1 connector was cracked and broken. It seems like someone has messed with it before.

 

[cruisermatt]

Unless you have good tight connections on the ENTIRE wire harness, you’re chasing your tail

 

[Seth S]

You might as well check the valve clearance while you are establishing baseline. Its also worth inspecting the cap and rotor...and measuring the resistance on the ignition cables.

 

[SteveH]

You may want to buy a neon spark tester and lay it on each spark plug wire and look for inconsistent spark, especially on #1. A neon tester should be in every toolkit for cases like this and those (sadly) in the future.

 

[vankho]

Thanks @SteveH. I went and added a spark tester to my tool box as well as a noid light and it was very helpful. I was able to confirm that there is power going through to spark plug. On the injector side, I was also able to get a flashing light on the injector connector. At this point, I'm thinking it's a clogged fuel injector and hoping it's not truly dead. Planning on getting them out and just sending the batch to get serviced and cleaned.

 

[cruisermatt]

Unless you have good tight connections on the ENTIRE wire harness, you’re chasing your tail

 

[vankho]

I plan on checking out the condition fuel injector harness and it's connectors since I'll have access to it this weekend. Any tips on how to approach diagnosing the ENTIRE wire harness @cruisermatt?

 

[cruisermatt]

One connector at a time. If it’s cracked, melted or locking tab is broken that’s just a large possibility you have a poor connection. That’s why it’s always the first thing I go to. Generally on a typical 250k mile 62 all the the injector plugs are broken, O2 sensor connectors or wiring is melted, TPS and IAC locking tabs broken, it’s all 30-32 year old plastic.

If you have more then one or two broken connectors I would just pull the whole harness. That sounds intimidating but it really is not bad.

Pull the upper intake plenum (6 bolts, few hoses, and a $12 gasket and you should be able to remove the entire engine harness fairly easily.

Once it’s on the bench it’s pretty simple to follow the schematic in the FSM and check the entire harness for resistance/continuity.

I have pretty much all the connectors sourced and can help you out with replacing whichever ones you need. I usually just replace the housings and leave the terminals alone unless they’re really bad.

Yes this is not a small task but in my opinion pretty much mandatory for any original FJ62 at this point. Your engine wiring needs to be verified as good as a baseline.

 

[vankho]

Made a lot of progress today. Removed the upper intake plenum and was able to see the condition of the harness. As you stated @cruisermatt, a lot of brittle and broken plastic, exposed wiring. The previous owner attempted to hold the thing together with zip ties. I decided to go ahead with pulling the entire harness to work on testing it, however I struggled with this small wire bundle behind the engine, that went under. I'm assuming it's going to the instrument panel?

Either way, this was a great way to see the condition of the harness and engine. I can't help but feel like I bit off more than I can chew here though lol

The intake, cold start injector, and EGR were also caked in, what I can only imagine is decades of, crud - so plenty of work ahead...

 

[cruisermatt]

The wiring that goes into the firewall (the left of the of the AC line pass-throughs) goes to the ECU). Pull the glove box, after that it's 4 connectors and it comes right out. From there it's the two O2 sensor plugs and that should be about it.

 

[FJACS]

Why do you suspect a head gasket leak? If you’re losing coolant - #1 plug might look like that from being steam cleaned...

But those busted connections aren’t helping at all. Get the replacement connector info from Matt and fix it all.

 

[vankho]

This morning I was able to remove the harness and confirm continuity through all connections, which is just good to know for peace of mind. However, as noted before, the condition of the harness leaves a lot to be desired. What would be the best way to address this? I'm tempted to unbind everything to wrap it with more modern materials...

I also had another opportunity to take a look at the fuel injectors and noticed that injector #1 pins were significantly off-centered. My current hypothesis to my misfire issues in cylinder 1 is that it may be due to this. It looks bent enough that it might not be entering the terminal on the connector?

 

[red66toy]

This morning I was able to remove the harness and confirm continuity through all connections, which is just good to know for peace of mind. However, as noted before, the condition of the harness leaves a lot to be desired. What would be the best way to address this? I'm tempted to unbind everything to wrap it with more modern materials...

View attachment 2592191

I also had another opportunity to take a look at the fuel injectors and noticed that injector #1 pins were significantly off-centered. My current hypothesis to my misfire issues in cylinder 1 is that it may be due to this. It looks bent enough that it might not be entering the terminal on the connector?
View attachment 2592197

Yikes, yeah that is likely the cause of your issues. I think the best way forward would be to replace those bad wire sections and re-wrap (as you indicated) in new material. I added some heat shield blanket material around my harness when I had my intake off.
Also, degraded harness issues is common in the 3FE, especially in the area where the harness takes that steep bend behind the intake support bracket by the fuel pulsation damper. That seems to be where this exposed and broken part is correct?

 

[Kleatus]

This morning I was able to remove the harness and confirm continuity through all connections, which is just good to know for peace of mind. However, as noted before, the condition of the harness leaves a lot to be desired. What would be the best way to address this? I'm tempted to unbind everything to wrap it with more modern materials...

View attachment 2592191

I also had another opportunity to take a look at the fuel injectors and noticed that injector #1 pins were significantly off-centered. My current hypothesis to my misfire issues in cylinder 1 is that it may be due to this. It looks bent enough that it might not be entering the terminal on the connector?
View attachment 2592197

I had issues when the air rail melted my harness like that. I was also getting many random codes and misfires. I had to cut apart the harness and splice in new wires. Once they are that cooked, you have to go back a little ways to get to pliable insulation and non-corroded wire.

 

[vankho]

No more popping sounds! No more hesitation! Super responsive and quick acceleration. So pleased to report back that it's firing on all cylinders and it feels like a completely different experience!

I ended up doing a lot to troubleshoot this issue, but if I had to narrow it down to one thing, I'd say it was due to poor connection from the harness connector to fuel injector #1. This might have been due to bent pins or the harness being in poor condition. By the time I saw it, I already had significant parts of the system torn down. I wished I was able to spot it earlier, I might has saved a lot of time and parts - but it was nice doing a bunch of other things just for peace of mind.

I did the following since I had a lot of the parts removed. Some pics below at various stages this past few weeks.
1. Sent injectors out to be cleaned
2. Installed new connectors for wire harness (thanks @cruisermatt!)
3. Repaired burned / corroded wire segments for harness (thanks @Kleatus @red66toy)
4. Cleaned throttle body
5. Cleaned EGR

Learned a lot with this repair. Thanks everyone here for your help and guidance.

Also had my fair share of beginner/noob mistakes:
1. Wish I replaced the injector seats when I had it all apart. Just realized it right now upon seeing the photos.
2. My torque wrench is unreliable and lead to a couple of broken bolt heads (not sure how I'm going to extract those)
3. Also noticed a new symptom I didn't have before - Bouncing RPM idle... not sure what's going on there. But that's another battle for another day...

 

[red66toy]

Great news and great work!

 

[cruisermatt]

every once in awhile I give good advice

Looks good. Glad you got it sorted out. Good call on the Euro high-heat harness tape. That will last even longer then the OEM loom.

 

[FJACS]

Nice work on this.

if the bolt heads broke off from being over tightened, they’ll come out quick with an easy out.

 

[cruisermatt]

Did i miss something? Why were you tightening head bolts?

 

[vankho]

Did i miss something? Why were you tightening head bolts?

I broke a bolt for cold start injector and fuel regulator. So it’s being held together with a single bolt each. Overtightened