Hey guys, I've been problem solving for a couple of weeks , but really need to get it running now!!

 

so! the car starts and runs fine, after about 5/10 miles it drops a cylinder and sounds like a Subaru

 

I've swapped (all working) ptu, maf, coil packs, plugs,cleaned the electrical contacts and a brand new coolant sensor, still no joy :(

 

All injectors seem to be ticking nicely, and tonight i've discovered that i have no spark on cylinder 4 ! all the rest spark fine!

 

please can you tell me where to start looking next?

 

I can turn the car off for an hour or so, it then starts fine with no issues then after a short drive, boom!! cylinder goes down

 

Cheers

PTU loom, also check the ECU end, might also be worth opening up the ECU to look for any issues on the board, might be a simple fix of broken down wire to the coil pack

Cheers Groover baby! will be on with that tomorrow :( hopefully an easy fix :o

Alot of injectors going lately on a few peeps motors, mine included, but if you definitely have no spark and youve changed the coil pack and PTU, then its likely a wire issue, good luck and let us know if you find the problem :thumbup1:

yep! deffo no spark! I will update this thread with my results :/...............cheers :alucard:

Edited May 13, 201411 yr by daZvert

That's what was happening to mine and the head gasket had gone

I really don't think my head gasket is gone, but never say never! But even though similar symptoms, your car would be loosing compression when it gets hot due to the gasket, but mine is loosing a spark, so most likely electrical mate. Fecking hope so anyway :0

 

That's what was happening to mine and the head gasket had gone

How about swapping coil packs and spark plugs between another cylinder to see if the fault moves. If it does your working coil and plug don't work, if it doesn't it's the wiring. I'd start the engine and move all the harness about check for any discolouration on terminals. Maybe even cont check the return and volts check the supplies. If that's all good I'd maybe borrow another maf ptu before changing the ecu

Done all that buddy :) deffo narrowed the problem on cylinder 4 only, I have a spare ecu, so gonna swap that over tonight ( easy swap) then look into the wiring :(

 

Does anyone have a diagram of the ptu loom, or does anyone know if it also joins up with some of the relays?

 

Thanks for all the help guys, it is appreciated :)

 

How about swapping coil packs and spark plugs between another cylinder to see if the fault moves. If it does your working coil and plug don't work, if it doesn't it's the wiring. I'd start the engine and move all the harness about check for any discolouration on terminals. Maybe even cont check the return and volts check the supplies. If that's all good I'd maybe borrow another maf ptu before changing the ecu

Here is the circuit diagram which includes the PTU:

 

http://www.300zx-twinturbo.com/cgi-bin/manual.cgi?list=efec&dir=&config=&refresh=&direction=forward&scale=0&cycle=off&slide=13&design=default&total=190

Daz, I had this same problem, twice a few years back. I swapped everything with known good working items and the non firing issued remained.

 

To cut a very long story short, I ended up opening the whole loom, ECU to PTU to Coil pack connector. Lo and behold the first issue was an easy spot! The –‘ve small wire from the coil pack loom had a tiny fracture and split. Somehow this loom would return the signal to the PTU when cold but as the engine and loom got hot, the signal was lost and I had no spark. The second was a little more complicated but turned out to be a similar issue.

 

A few months later the same happened but this time on the dreaded No 6 cylinder! Again I swapped out all items for known working ones……no joy! AlanZ off here then joined me and we swapped out ECU’s both worked on his car but not on mine….ummmm??? It was time to open up the nicely and recently re-loomed wires! This time I had a small amount of insulation missing off one of the –‘ve wires from the ECU this was shorting off the metal frame that the ECU is bolted to in the footwell.

 

So, my issue…..Brittle Wire Disease!

Nice one guys! Thanks for the diagram Andrew :)

 

Ewwww Osty! Bet that was a nightmare unravelling all that loom :( Glad you got it sorted though mate. Looks like that's tonight's mission for me :( still gonna try the ecu first, then attempt the looming loom!!

 

Cheers peeps, appreciate everyones input x

Sounds like a nightmare mate but to be honest is not as bad as you think. It also allows you to very quickly quickly ascertain the condition of the loom. Its also a good excuse to tidy up the wiring.

 

Get a volt meter on the Coil pack connector and check for signaling voltage. Do the same on a working connector to recognise differences.

 

Hope you sort it mate.