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Gav's 200sx RPS13 1JZGTE of race car.


~Slideways~

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Thanks guys. Really appreciate the extra eyes on trying to figure this one out.

Just had some time now and the first thing I checked is the sense wire on the alternator plug. Pulled back the covering and the sense wire outer layer has split! The inner core looks ok so may not actually be a problem. This plug and three wires I had kept from the donor jzx100 body loom. One of the only plugs on the engine I didn’t replace with new.

The core of the wire looks ok, I hoped it would be obviously corroded but it isn’t.

Im going to buy a new plug and pins and cut the wire back to some fresh stuff. This plug is brittle like most old Toyota ones are.

It may not be the issue but it needs sorting out anyway.

 

It is currently getting its sense power from a  shared constant power wire which is original to the Nissan chassis. I’ll try wire it directly to the positive cable from the battery in case there is some resistance giving it incorrect voltage and making it over charge.

 

D81EEC77-D3B1-4BC3-A72D-5F735F28C967.jpeg.405082089ceb975fb8ff860e2304f42d.jpeg
 

It’s worse now that I have removed the pin.

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Also fitted a turbo beanie thing:

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On 09/07/2020 at 12:32, ~Slideways~ said:

 Just before that point I was engine braking for a couple of minutes around 30-40kph down hill in slow traffic when I noticed it sounded wrong. So I decided to test if ign off and on would fix it, which it did. This is strange because the ECU would have still been on since it has ECU hold power enabled. 

This will be the bit I was looking at, and scratching my head. Ididn't think about a long downhill, I assumed it was all idle.. 

It might be worth reviewing the fuel cut on over-run to see if its enabled, and maybe switch it off for a test.. 

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Just now, mjrstar said:

This will be the bit I was looking at, and scratching my head. Ididn't think about a long downhill, I assumed it was all idle.. 

It might be worth reviewing the fuel cut on over-run to see if its enabled, and maybe switch it off for a test.. 

Definitely worth checking, although the misfire thing can happen at part throttle like on the motorway sitting at 100kph for a few minutes and its fine then with no change at all, it just happens and goes away by itself.

I'm hoping its going to be something simple like a bad earth or the bad sense wire. Or even if the new alternator is stuffed, at least I'd have an answer.

 

 

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Fitted new alternator plug, new pins and moved the sense wire to a better power source (theoretically).

At idle it’s fine. A little more revs and it’s going to 15.3v. 


Balls. It must be the voltage regulator. The alternator will be out of warranty now too. It was meant to be ‘all new parts’.

I still have the old alternator which stopped charging. Maybe the reg in that will be ok.

Otherwise I’ll look into whether I can get a new regulator to fit to this refurbished one.
 

 

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Fuuuuuuck, I’ve put in a brand new voltage regulator and I thought it was okay because the log in PC Link showed 13.89v at idle. But give it some revs and it jumps to over 16v.

WTF is going on?

My multimeter reports 14.4v at idle and it’s not showing any higher when I rev it.
 

Either the Link is some how reporting incorrect voltage readings or my multimeter is wrong.
 

Is there no voltage problem at all and there is some other problem causing the misfire?

 

 

 

 

 

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Good suggestions guys thanks. I had also emailed Link support about the difference in readings between the Link log and a multi-meter and they said it could be due to having a diode in the 12v feed to the ECU, as this feed is also used to return the voltage spikes from the switching of solenoids and relays. (I never would have thought it did anymore than provide power to the ECU) 
 

So if a ISC or boost control solenoid is switching, and a big one would be the injectors then this back EMF will build up and pump up the ECU voltage. 

I had asked about the diode since I had installed one after not being able to find the source of the power back feeding. It sounds like it's more complicated than simple wiring since he's talking about EMF's. 

Anyway, late last night I removed the diode and now the log shows the same voltage as the mutli-meter plus it seems like it is a steady 14.7v even when rev'd to 4000rpm (directly below sleeping children...). I didn't have time to drive it, so I'll try do that tonight after the kids are in bed.

Bit of a frustrating thing but it looks like I'm getting to the bottom of it.

In saying that, it may not having anything to do with the misfire. It does sound feasible that the ecu is getting confused with incorrect voltage though.

Maybe one day I'll actually be able to 'finish' this one!....

 

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  • 2 months later...

Still chasing this misfire, currently have injectors out, which were new xSpurt 1000cc's when put in some time over a year ago. 

They were tested and it sounds like one was a little iffy on a low pulse, but was then fine which is frustrating. But it does actually match the intermittentness of the misfire. I'm not sure its enough to explain the behavior I'm seeing, but maybe since it only happens at idle/low throttle cruise which would be a pretty low duty cycle on big injectors, it could fit.

Getting them ultrasonically cleaned, if that doesn't do anything then maybe I'll just have to buy one new injector and hope for the best.

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  • 3 months later...
  • 7 months later...

Since the last update I've put a few thousand km's on it, every time I am impressed by how responsive it is with the relatively big HX35. The exhaust manifold with the small runners must have really helped make it spool early, most likely meaning some restriction in high revs but man it's so good.

It STILL has the mystery intermittent misfire. It has a brand new genuine Crank Angle Sensor and I've borrowed a spare R35 coil and tried it in all six position with no change. Takes ages to test since it sometimes will not have the misfire until 30min into a drive, sometimes within 2min.

Every time, it goes away if you let it drop to idle. i.e. doesn't come back immediately no matter what the conditions are. But if its doing it and you increase revs, even with clutch in, it will continue to misfire until you let it drop to idle. Bloody frustrating.

So I guess I've confirmed it isn't a faulty coil, unless its more than one.

Next I'll be trying a temporary constant power to the coils to bypass the relay and loom.

The heavy duty clutch, went in earlier in the year and it went on the dyno again. Developed a misfire after being on the dyno for more runs than previous, so likely heat soaked etc, changing the crank sensor filter improved it. Once I came to pick it up, it was still on the dyno and had cooled down. Plan was to show me it misfiring, but it did clean runs, I guess because it had cooled. So I ordered a stupidly expensive genuine sensor.

The sensor has been in for a few months, but too busy to do more dyno time and I wanted to try swapping the known good coil.

So I am enjoying driving it greatly it's just like this ongoing 5% of the time problem type thing. I move onto another project for a while until I have the enthusiasm to do more 200sx testing.

Here are some photo's from putting in the new clutch, took the opportunity to put in some heat shielding since the tunnel gets really hot:

 

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Clutch and flywheel:

 

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The other day it randomly blew the fuel pump fuse, driving home from work and the engine died. I keep a laptop in the car to connect to the Link and everything seemed fine until I realised I couldn't hear the fuel pump.

Really weird failure, it looks like the fuse had been getting hot and melting stuff well before it blew. Work mate suggests it could have been corrosion causing resistance?

This is a dedicated power wire from the battery, which is triggered by a relay and the ecu. Strangely it has been fine for almost 2 years...

Nasty:

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I got it home totally fine with a spare fuse. 

Have now replaced the whole thing.

 

Also the clutch took about 1000km to be much nicer to use.

 

 

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25 minutes ago, chris r said:

Could the random miss be fuel supply issues due to the the burnt fuse holder? Going back down to idle let's pressie build back up? 

 

Do you have logging of fuel pressure when it's playing up? 

This.

The fuse holder probably just china'd out. Have seen it a few times in various applications.

I always check the the fuse is a nice tight fit into the terminals. If not, give it a bit of a pinch up with the pliers to close the female parts up.

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On 20/08/2021 at 20:31, chris r said:

Could the random miss be fuel supply issues due to the the burnt fuse holder? Going back down to idle let's pressie build back up? 

 

Do you have logging of fuel pressure when it's playing up? 

It does fit with the behaviour of stopping when it drops to idle doesn't it?

Good thinking, I hadn't thought of that connection.

I just need an essential driving pass now haha

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Will test it in Level 3. Having been sanding the MX5.

Here is a photo of the weird fuel pump fuse failure.

It's inside the cabin and no chance to get wet, its parked in the garage and has been in use for almost 2 years and 1000's of km's. Has it been a bad contact for all of that time causing the metal to break down/corrode?

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  • 2 weeks later...
  • 3 weeks later...

I've changed the power feed wires to the coils to a much bigger gauge all the way from the relay to coil plug pins. Thought maybe there could be resistance that got worse with heat?

Made no difference at all.

Still bloody fun to drive though...

Maybe its something to do with the earthing? I have a huge list of things I've tried so far, one day I'll crack the bastard.

----------------

 

Bought a battery cut off switch thing ages ago so since I desperately need to be doing sanding on the mx5, I made this:

I cut the power cable which goes to the battery behind the passenger seat and crimped on some lugs so it joins here.

Made a basic plate out of aluminium and covered it in fake carbon wrap because it looks fast.

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Decided to have it set back a bit so there is plenty of room for gearshifts.

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It isn't actually finished, I was planning to drive it to work today but it was late and freezing. Just need to drill mounting holes then connect the cables and insulate etc.

 

 

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