Hi guys

 

I had a 4 second misfire a while back and ignored it. Went for a blast the other day and got a permanent misfire on number 1.

Ive swapped the coil for number 2 and the issue is still with cylinder 1.

 

Im yet to check the spark plug, wiring seems ok though, even though all the coil connectors just pull off (tabs snapped off)

It looks like a series 2 ptu, is there anything else i should look at?

Thanks

Mark

Try the injector connection, bet its green.

 

Jeff

Good point, will check tonight. I have a spare set of plugs infact that I never got round to fitting on the last one.

Had a look at the connectors. All green so I cleaned them all. Along with the ptu, coil plugs and throttle position switch as it was right there. And still on 5. I pulled the plug on the injector and no change. So injector and coil unresponsive. Went to take the spark plug out and remembered I don't have my tools arm. So will get that out this weekend to see what's going on.

Is the spark plug wet on no 1 cylinder,may be the injector itself,seeing more and more of this now.

I'm hoping to find a knackered spark plug. Will have a look when I get my tools. Snapped my 1/4 ratchet and left my others at a friends. Rubbish

Sparks are fine. As are the injector wiring. It looks like the plenum has had the dremel treatment as there's swarf everywhere but I still cant get injectors out or even undone.

Without taking the plenum off to change an injector are the injector treatments any good and worth a try?

No if the injector is dead thats the end of it,search up the dremel method it does work,youll need a long screwdriver to undo the cap screws,give them a tap first to free them,dont go wild or you will distort the heads and the screwdriver wont undo them.

may be the injector itself,seeing more and more of this now.

 

Are the injector failures you are seeing mechanical (ie pintel) or electrical (coil)?

Too late. The screw heads are already rounded off. Seems like this problem has happened before. I'm going to have to take the plenum off I think.

Can I test resistance before I take it out to check it?

Yes, across the two connection pins.

Can I test resistance before I take it out to check it?

 

FSM resistance specs for injectors:

 

efec-193.pdf

Thanks guys. Am I missing something or should it show resistance with no power or plug on it. Because I'm getting nothing on the offender or another injector.

Also not getting 12v on ignition to either plug. But I am getting it on the coils

You won't get 12v across the injector connector. They are constantly live and then the ECU makes the circuit by grounding it. The plug only supplies live. You will have to put the meter on the battery neg or block and the positive to the right pin.

 

You want your meter on ohms which is the horse shoe type icon, then with clean pins you should see 10-14ohms. If your meter is saying 1 on the left with nothing on the right that means the circuit is open. The resistance is infinite. The most likely cause of this if they are all saying this and you know they work is the pins are dirty. I suspect though your not using the meter correctly.

Ok. I got battery voltage to injectors. Offending and normal one. So the wiring although green is ok and functions.

I got a resistance of 12.4 on a good injector but still couldn't get a resistance on the offender. I tried to clean up the connections but still nothing. I have left some uls in the injector and ill try again tomorrow.

That may be your issue then, the injector has failed open circuit. Giving you Infinite resistance.

It is like it has just failed. Since its started I've bot been able to get it working again. So maybe it has completely died now. I shall try my best to get it out without taking the plenum off.

Before I take it out, I forgot I have conzult. Will this confirm or show anything wrong?

conzult will show you which cylinder is not functioning (through the power-balance test or it shows up as a misfire error), but you already know which cylinder it is.

The conzult can't "see" if a particular injector has failed.

 

While you are at it, I'd check the resistance on all injectors...they usually start failing one by one.

Also it is recommended to disable the permanent live feed on the injectors, as this live feed (which is always on, even with ignition off) plus the ethanol in modern fuels is what causes the injectors on the early 300ZX models to fail.

 

http://twinturbo.net/nissan/300zx/forums/technical/view/1109134/Switch-injector-voltage-mod-in-1-2-3.html

Thats an interesting mod, does the ecu not give permenant live for a reason. Does it take longer to fire on ignition with that mod done?

I shall test them all, even the hard ones to get to at the back and list here.

Thanks

Thats an interesting mod, does the ecu not give permenant live for a reason. Does it take longer to fire on ignition with that mod done?

 

I did that mod a while back and it works fine:

 

http://www.300zx.co.uk/forums/showthread.php?171664

I will look into it. thanks

Are the injector failures you are seeing mechanical (ie pintel) or electrical (coil)?

 

Hi Andrew,most common is high impedance in the coil causing bad spray pattern or they go open circuit and dont trigger at all.

Well shit! Its definitely the problem now.

I still couldn't get a resistance off it and it practically fell apart. So it must have been the problem all along.

Plenum will need to come off now. Will put new connectors on and may have to find coil plugs as well as I annihilated one shutting the bonnet. Plus they're all broken.

So the plenum is coming off now. Im trying to buy a gasket in preparation on this website https://iapunitedkingdom.com/ for £3.34, but its not letting me.

I cant post in the wanted section so hoping mjp is reading this, I need one please.

As far as I know Mike is still in hospital so you will have a wait.