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1983 280zx N/A
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Discussion Starter #1
Howdy folks, I was driving my 83 zx the other night and popped the hood to check the fuel pressure and noticed the exhaust header was glowing dull red between cylinders 3 and 4. My infrared thermometer measured the area being over 700 degrees with the surrounding pipes being around 650. I thought it was because I was running too lean (AEM wide band module was reading 13:1 to 15:1) so I unplugged the o2 sensor and brought it back down to between 11:1 to 13:1 and the header still starts glowing red under normal driving!

I checked ignition timing and im still set at 8 degrees BTDC, cam timing indicators still line up properly but I noticed the spark plug in cylinder 3 and 6 were black and sooty.

Has anyone else had this issue running headers before? I wrapped mine in the rockwool insulator wrap if that adds to anything. I'm just trying to figure out what's causing this to happen. Starting to get nervous my cam timing or crank pulley is messed up somehow!
 

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Howdy folks, I was driving my 83 zx the other night and popped the hood to check the fuel pressure and noticed the exhaust header was glowing dull red between cylinders 3 and 4. My infrared thermometer measured the area being over 700 degrees with the surrounding pipes being around 650. I thought it was because I was running too lean (AEM wide band module was reading 13:1 to 15:1) so I unplugged the o2 sensor and brought it back down to between 11:1 to 13:1 and the header still starts glowing red under normal driving!

I checked ignition timing and im still set at 8 degrees BTDC, cam timing indicators still line up properly but I noticed the spark plug in cylinder 3 and 6 were black and sooty.

Has anyone else had this issue running headers before? I wrapped mine in the rockwool insulator wrap if that adds to anything. I'm just trying to figure out what's causing this to happen. Starting to get nervous my cam timing or crank pulley is messed up somehow!
Can be caused by rich mixture, late ignition timing, incorrect valve timing, I would check that the timing marks on the damper pulley are correct with number one cylinder at TDC.
 

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Discussion Starter #3
The crank timing marks line up on the pulley, and I can see cylinder 1 is at tdc. I havent done the chopstick method to 100% confirm but i can see the piston start to travel downwards after it passes the 0 degree mark on the timing plate.

Could a bad spark plug connection cause similar issues? The connectors separated from the wires and look like theres some black buildup on the connector.
 

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The crank timing marks line up on the pulley, and I can see cylinder 1 is at tdc. I havent done the chopstick method to 100% confirm but i can see the piston start to travel downwards after it passes the 0 degree mark on the timing plate.

Could a bad spark plug connection cause similar issues? The connectors separated from the wires and look like theres some black buildup on the connector.
If the secondary voltage is going to ground it should be running rough from missing cylinders. You said two plugs looked sooty and black. What did the other four look like?
 

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1983 280zx N/A
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Discussion Starter #5
Other 4 plugs looked fine. They're new NGK iridium plugs with about 75 miles on them and other than #3 and #6 they still look almost new.

If those 2 plugs had a poor connection and weren't getting enough spark could it cause the gas mixture in the cylinder to ignite slower/continue to burn when the exhaust valve is opening?
 

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Other 4 plugs looked fine. They're new NGK iridium plugs with about 75 miles on them and other than #3 and #6 they still look almost new.

If those 2 plugs had a poor connection and weren't getting enough spark could it cause the gas mixture in the cylinder to ignite slower/continue to burn when the exhaust valve is opening?
No it would not light slower. I am wondering if you have an injector problem. Make sure that the ignition is proper. I then would swap injectors from the cleanest to dirty cylinder and see if the problem follows the injector
 

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No it would not light slower. I am wondering if you have an injector problem. Make sure that the ignition is proper. I then would swap injectors from the cleanest to dirty cylinder and see if the problem follows the injector
I am assuming that you have good compression in the dirty cylinders.
 

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Discussion Starter #8
Yes good compression in all 6 cylinders, between 170 and 180 (?) Psi. New rings and standard brand injectors from zcardepot. Could too much fuel in those cylinders be causing the headers to glow?
 

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Yes good compression in all 6 cylinders, between 170 and 180 (?) Psi. New rings and standard brand injectors from zcardepot. Could too much fuel in those cylinders be causing the headers to glow?
Yes too much fuel is classic symptom. Fuel is still burning in the header tube. That is why I suggested swapping injectors between cylinders.
 

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Discussion Starter #10
Makes total sense. I'm gonna try and clean the connectors real good first and see if that helps, the fuel rail is a real PITA to remove haha. Thanks for all your help! This is my first major overhaul/rebuild project and I swear once I think I have something figured out I realize there's still TONS I still don't know! All worth it though.
 

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Makes total sense. I'm gonna try and clean the connectors real good first and see if that helps, the fuel rail is a real PITA to remove haha. Thanks for all your help! This is my first major overhaul/rebuild project and I swear once I think I have something figured out I realize there's still TONS I still don't know! All worth it though.
You like to learn thinks. That is good. If those cylinders are running extremely rich it will wash down the cylinder walls and that is not a good situation especially on a new bore and piston rings.

Let me know what you find.
 

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You like to learn thinks. That is good. If those cylinders are running extremely rich it will wash down the cylinder walls and that is not a good situation especially on a new bore and piston rings.

Let me know what you find.
FYI The oxygen sensor is reading the average of all cylinders. If you have one cylinder is running too rich the oxygen will lean down the average. The outcome is one cylinder still running rich and the remaining cylinders running too lean bur the average looks normal
 

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It is possible that two of your injectors are messed up and don't have a good spray pattern. In some cases when this happens the injectors may be squirting part liquid and part atomized fuel. The liquid won't burn good if at all causing a very rich condition. It's more frequent on old injectors, especially if they've been sitting but it can happen on new injectors as well. Standard injectors are not a good quality injector, I've had to replace quite a few of them that were less than 2 years old. Most new injectors have a lower quality control issue except for Bosch. Bosch injectors are incredibly expensive and hard to find. That's why I went to the injectors that I sell. The rebuilt injectors that I sell have a very high quality control rating at less than 2% warranty/return ratio. That's as good as it can get. Only the metal housing and the needle are reused. All the rest of the components are brand new and the internal seal is impervious to alcohol. You can always try running some injector cleaner through the system, possibly even Seafoam gas treatment, but don't hold your breath.
I've also seen the distributor module cause a situation like you're experiencing but that usually affects all 6 cylinders the same. Z man of Washington
 

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Discussion Starter #14
Sorry for the late reply everyone, I haven't had much time to work on the ZX due to the weather (no heat in the barn yet), but I was able to get a cardone refurbished distributor and new NGK spark plug wires installed. I think the issue was the vacuum advance being shot and stuck closed, causing retarded ignition timing at cruising rpms.

Afterwards I was having a **** of a time getting ignition timing set right, I was maxed out of adjustment and either way too advanced or retarded even with moving the spindle a tooth either side. checked TDC with a TDC tool and was about 2-3mm off according to the timing mark on the crank pulley. Got a new OEM 3 row pulley from Lynchburg Nissan and was able to get it right at 8° BTDC and still have room for adjustment!

Now need to get her all buttoned back up for some road testing!
 

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Sorry for the late reply everyone, I haven't had much time to work on the ZX due to the weather (no heat in the barn yet), but I was able to get a cardone refurbished distributor and new NGK spark plug wires installed. I think the issue was the vacuum advance being shot and stuck closed, causing retarded ignition timing at cruising rpms.

Afterwards I was having a **** of a time getting ignition timing set right, I was maxed out of adjustment and either way too advanced or retarded even with moving the spindle a tooth either side. checked TDC with a TDC tool and was about 2-3mm off according to the timing mark on the crank pulley. Got a new OEM 3 row pulley from Lynchburg Nissan and was able to get it right at 8° BTDC and still have room for adjustment!

Now need to get her all buttoned back up for some road testing!
Sorry for the late reply everyone, I haven't had much time to work on the ZX due to the weather (no heat in the barn yet), but I was able to get a cardone refurbished distributor and new NGK spark plug wires installed. I think the issue was the vacuum advance being shot and stuck closed, causing retarded ignition timing at cruising rpms.

Afterwards I was having a **** of a time getting ignition timing set right, I was maxed out of adjustment and either way too advanced or retarded even with moving the spindle a tooth either side. checked TDC with a TDC tool and was about 2-3mm off according to the timing mark on the crank pulley. Got a new OEM 3 row pulley from Lynchburg Nissan and was able to get it right at 8° BTDC and still have room for adjustment!

Now need to get her all buttoned back up for some road testing!
The vacuum advance would affect all of the cylinders. Not likely the problem.
 

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Discussion Starter #16
The vacuum advance would affect all of the cylinders. Not likely the problem.
Yupp still glowing. Guess I need to pull the injectors off again and test them?

It's more responsive now though!
 

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Discussion Starter #17
Another thing I forgot to mention was that I have the header wrapped... could that be an issue also??
 

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Header wrapping will trap heat inside the tube. However if all cylinders are wrapped they should all look about the same.

I still think you have an injector problem that is causing a rich mixture in the problem cylinders.
 

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Discussion Starter #19
Okay, another update. Fuel pump died on me so I replaced it with a new Nissan part. Ran one tank of seafoam, then one tank of Lucas fuel treatment, and removed the header wrap. She runs much smoother now, and header isn't glowing as much. Im still trying to replace the injectors as im not very confident with the Standard brand ones I have in there now but I am having a hard time finding info on what injectors are good for the N/A '83 engine. I've adjusted the tps to where the fsm says but the afm still bounces between 12:1 to 15:1 between 2k and 5k rpms. Definitely leads me to a malfunctioning injector?

Anyways, what's a good/reputable vendor for refurbished/new injectors?? Zman I know you said you sell them but I could not find you online.
 
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