1JZ Misfiring, Diagnosis

[paulb1320]

Hi guys,

My 1JZ is having the misfiring under boost problem. I've been searching and I've checked the usual culprits and I have some concerns

1) The cam/crank sensors resistance was in spec but both cam sensors had some oil in them.

2) 4/6 of my coil pack connectors were busted on the inside so I've ordered a new set, they still plug in good but there are no locking tabs and some of the pins are pushed back slightly. The coil packs themselves are in good shape with no cracks whatsoever

3) I got the map sensor with my engine and the seller had glued on another barb because he snapped the old one off. The engine runs and idles decent and when I unplug the Map the engine dies out so I think it is working but how can I test it to be sure.

4) I opened up my ECU to check for leaking caps and everything seemed good, no signs of leakage. Can the caps still be leaking without leaving visual evidence, and is there any way to test that this ECU is working properly?

5) I'm having issues with my cluster so I can't pull the codes. Is there any other way to check the codes.


If someone could please help me single out why my car is backfiring it would be greatly appreciated.

Thanks in advance.

 

[hvyman]

Did you pull the blue boots off the coil packs?

What are your plugs gapped to?

 

[paulb1320]

Did you pull the blue boots off the coil packs?

What are your plugs gapped to?

Yup I pulled the blue boots off and no cracks their either. I don't know what the plugs are gapped to, I haven't changed them yet. I just pulled them to check and they are nearly new NGK iridiums. I'll check the gap asap

 

[Turbo Habanero]

Pick some bk7re plugs Part #4644 gap them to .028

How much boost is it running ?

Does the car have a wideband? If so why are the AFR's reading at ?

 

[hvyman]

Iridiums are a pain to gap. There prolly at pre packaged gap which is any where from around 36 to 46. Boost on a jz will blow that out fast.

Get ngk coppers like habenaro said. Pn 4644. Gap to 25-28 and should be good to go.

 

[paulb1320]

I was going to gap them today but I couldn't find my gauge. Do you guys think the plugs are the issue?

 

[Turbo Habanero]

I think its a possibility

 

[te72]

I was going to gap them today but I couldn't find my gauge. Do you guys think the plugs are the issue?

If everything else seems to be correct, then that would be my first guess. Easy thing to check too. Buy a new gauge and a set of plugs while you're at it. Never hurts to carry spares in the car.

 

[paulb1320]

Ok guys I'm bumping this up because I am just now getting time to work on my car again and I'm still having this issue. Here are the things I have tried since I last posted ITT.

Gapped my plugs
Checked my wiring for the umpteenth time (for the record I did not extend my harness just reroute and spliced/extended the body plugs, I also noticed that someone had been in the harness before me)
Got ECU recapped from DM
Changed both Cam sensors since they were full of oil
Replaced the map sensor (snapped the nipple of the old one so I had to)
Checked my timing
Checked to see if red wire on TPS is getting 12v (it is)
After that I started checking my grounds, confirming I had good metal-metal contact at all the ground points. Can someone give me a list of all the grounding points for both the engine and chassis harness I want to ensure that I didn't miss any grounding points.

After having no luck with everything, a local mechanic told me to check my igniter ground and also hook up the ignition noise filter, I told him I didn't have the female side for the noise filter and he said just to ground both wires (can someone confirm if this is correct because I am not sure). So I did as he suggested and ran a new ground from the igniter to the chassis (following the diagram below) and ran both wires of the ignition noise filter to the same ground. After that it wouldn't start, as soon as I reconnected the old ground wire for the igniter and removed the filter wires from the ground it started back up and had the same running rich, misfire, sputtering issue. How can I test to see if the igniter itself is faulty?


I cut and ran the white wire (pin 4) on connector A to a ground on the chassis and it wouldn't start.

If someone could please give me some help on what I did wrong or what I should try next I would greatly appreciate it.
Thanks in advance.

 

[paulb1320]

Anyone?

Here's the TL;DR of my last post
1) Does anyone have a list of ground points for the 1JZ engine and the MA70 chassis harness?
2)Is it possible to hookup the ignition noise filter without the female end? Could this be the culprit of my misfire, sputtering problem?
3) Why didn't my igniter work when I re-did the ground, did I use the correct wire (white, pin 4 of connector A)?
4) How can I test to see if the igniter isn't faulty?
5) Any other ideas of what to check?

Thanks in advance.

 

[str8_6]

pull the coil plugs one by one...if when you pull one and it stops missing or nothing happens then you found your culprit.

What I would do next if say...cylinder number 4...you pulled the coil plug and it stopped backfiring, I would jump a wire from the igniter straight to the plug. Just find the same color for the positive side.

I was recently working on 1jz backfire issue and found that there was a break or weak connection causing the coil to spark but not spark enough..causing massive backfire. once i jumped it to bypass the original wiring the backfire went away and it ran much better.

 

[paulb1320]

I'll give that a try, thank you.

 

[paulb1320]

Ok guys I've run into another problem, the car won't start now. It's getting no spark, no power to the igniter and I'm not sure if it's related or not but I'm not getting power to the TPS either. I must have crossed and blown something while messing around with the igniter/noise filter. I've checked the fuses in the engine bay and I found that only the 30amp big fuse (IIRC it's labelled AM2 on the diagram) was blown. I replaced it and it still won't start, could it be one of the relays in the engine bay fuse box or perhaps a fuse in the interior fuse boxes?