Hi Guys, The cars been going okay since i changed the part at the end of the wiring loom in front of the fan, cant remember its name for the life of me. But now its started to misfire again, i'm slowly going up the wall, One thing that i changed on my merc when it misfired was the Air flow sensor, Something i've not thought of changing in the Zed. Anyone got one or can recommend a place, cars a series 1 '90 N/A Auto. Shouldn't have got rid of my spare one...

 

Rich

You mean the PTU? What did you replace it with (S1 or S2 PTU)? Did you clean the connectors?

I have recently solved a misfire problem, for some strange reason it turned out to be a faulty plug!

Not saying that this is the case in your instance, it's just that I checked, cleaned, greased every damn connector under the sun to no avail.

Could not believe a new set of plugs could make such a difference.

Andrew hi, PTU, thats the name, yeah, cleaned it all , it was a series 1 as well, immediately fixed the misfire, until now.

Redwine, plugs... worth a shot...I'm sure there has been a thousand and one fixes out there, just need to find mine

 

Rich

Right Then, Tried TWO bought PTU's S1 1 st one was worse than and the other was the same as mine ie gave middle cylinder drivers side misfire. Really only leave a couple of causes now, the Injector or the wiring/connector.

 

So are there ways to test on the car or do i have to resort to the old fashioned way.... just keep replacing stuff till it fixes it..

 

Regards

 

Rich

Right Then, Tried TWO bought PTU's S1 1 st one was worse

 

In what way?

 

Did you follow up on this post of yours?

 

https://www.300zx.co.uk/forums/showthread.php?187839-Spark-plug-advice

Hi Andrew, yeah, did all, thanks but made no difference, What i was trying to ask about the plug was ..if the injector was working would the plug look like this, or vice versa, if it wasn't working would the plug look like this, along those lines, Also if the injector was working but the wiring was crap, surely the cylinder would flood, big smell of petrol and the plug would maybe be "wet", I dunno, i'm no expert

 

is there a way to check continuity or resistance etc on the plug to the PTU, to check the wiring?

 

if any one knows please advise

 

Rich

Hi Andrew, yeah, did all, thanks but made no difference, What i was trying to ask about the plug was ..if the injector was working would the plug look like this, or vice versa, if it wasn't working would the plug look like this, along those lines, Also if the injector was working but the wiring was crap, surely the cylinder would flood, big smell of petrol and the plug would maybe be "wet", I dunno, i'm no expert

 

Have done some research online and there are some indicators and tips to check the packs/injectors etc. so i'll try that lot.

 

Regards

 

Rich

Have you been through the basics? Worked out if its loss of spark or fuel?

Stephen, hi. i'm doing that tomorrow. i'll let you know.

 

Thanks all

 

Rich

Check the resistance of the injectors, should be between... 10 - 14 kOhms

I used a spare connector with tails, but you can get the meter probes in with a bit of care, albeit a bit of a fiddle.

 

Did you change the plugs by the way?

A quick check for the injectors is to use a long fine screwdriver placed on the injector cap (engine running) and put your ear to the handle end, you should hear the injector ticking if it is working correctly, no tick signifies non working. You can then check to see if power is getting to it via the connector.

Hi Guys, Well its bad news, its the injector, checked both pack/plug assemblies of a good cyl against the bad one, the misfiring cylinder has sparks a plenty also when swapped to the good cylinder, so the sparks okay, which would mean the PTU is giving it, which means its okay (dam), which only leaves the injector, Did the screwdriver test and the good ones really did click but the bad cyl was just not there, probably heard the good injectors firing. So i've changed an injector before which included drilling away the plenum. Wouldn't wish this job on anyone...its a beatch.

 

Ah well, just dig out the drill, good job i hadn't put the polished plenum on......

 

Rich

Have you tested the connection to the injectior yet, these fail quite readily.

Drilling the plenum isn't that bad with the dremmel.

I used WD40 to stop the grinder clogging.

Also use a pair of long nose grips to break the screw.

Getting the injector out can be challenging!

opps.. forgot about the injector taking power, i'll try and check it out, does it get its pulse from the PTU as well?

No, the Injector harness is perminent live with a switched earth from the ECU. Simply shoving the meter probes up it on 12v dc won't help. I believe from memory you must put the negative from your MM to a suitable ground and the positive on the plug with the MM on 12v AC as it's a pulse signal.

Which number injector is it dude, #3?

Its the middle cylinder , drivers side... Man...

 

Depending where you look its a variety of numbers

 

Regards

Dude

That'll be number 3 then Mr Dude [emoji41] Are you going to replace it with a used stock injector?

Yeah i bought a spare injector last year, gonna check the connection first before i start machining the plenum away. Where abouts in essex are you Joely?

 

MR Dude

 

- - - Updated - - -

 

No, the Injector harness is perminent live with a switched earth from the ECU. Simply shoving the meter probes up it on 12v dc won't help. I believe from memory you must put the negative from your MM to a suitable ground and the positive on the plug with the MM on 12v AC as it's a pulse signal.

 

Stephen, these MM checks, are they taken with engine running of not?

 

cheers

 

rich

Yup running. Non running you'd get 12v dc which tells you, by much.

I was just wondering, could this be the cause of the misfire.....

I was just wondering, could this be the cause of the misfire.....

100%

 

I'm surprised you haven't checked it yet.

Have you tested the connection to the injectior yet, these fail quite readily.

 

Also did you chop that injector plug off?

I was just wondering, could this be the cause of the misfire.....

 

We've diagnosed your problem sir, your arm appears to have fallen off. :lol:

Ok, i've put my arm back on and the state of play now is:

 

put a new tail on, sprayed the injector side with that special spray, cleaned the contacts really well, put it all together and fired her up. Then kicked the gate, fence and then the cat,!!! Bugger, no difference. After going to my shed and having a good cry, i sort myself out and think what else can i try before grinding the plenum away......

 

i suppose the next best thing would be to check if any power, and the right power was coming down the line, i recall a chat with Stephen about it, i'll do some research and see what pops up.

 

Any more info and advice gladly received

 

Rich