Righto, so i recently bought another n/a Z. Manual 1992. It has been sitting for an unknown ammount of time. Previous owner told me it has been sitting for a month prior to the time of sale, it sat for a further 2 weeks at my house. Some documentation would suggest the car either sat for closer to 18 months or was driven a mere 2900km inside that time, considering his story was that it used to be a daily driver i'm not really sure what to believe. Anyways, the misfire/hesitation issue that im experiencing only happens under load below 3000rpm. It chugs, sputters and carries on in any gear below that rpm with the only exception being cruising at 100kph with my foot just sitting on the throttle. It runs a little cleaner when cold and gets worse as it warms up. Above 3000rpm it pulls like it should until about 6000rpm and then it sounds and feels like it struggles to go any further. Originally i was seeing code 21, Ignition circuit. I replaced the PTU and checked the wiring, reset the ECU and got code 55. The problem seemed to clear up a little bit, but not much however it no longer threw code 21. Ever since, only code 55 (all clear) So far i have changed the oil and oil filter, swapped in a fresh set of NGK plugs, dumped the fuel, refilled with fresh fuel and added an additive to clean the injectors, lines and absorb moisture and fungus and changed the fuel filter. I have used contact cleaner on and reseated the connections for the CAS, AFM, TPS, PTU, Coolant Temp Sensor, Coilpacks, Injectors, DET Sensor & O2's. I have checked spark visually for each of the coilpacks, checked the wiring and performed continuity tests. I have been told to count the teeth on the timing belt, Which i plan to do at the next Z Tech day this weekend coming with the assistance of someone else. My purpose is to also gather opinions and possibilities before attending so i can cover as much as possible. I have not performed a compression test, considering the motor has 113,000km on it (and its the real deal) i doubt compression will be low, i will have it double checked at the tech day. Timing COULD be out a tooth, this will be checked. The car was sold to me with no documentation other than the 2 years that he owned it, 100,000km service was completed by a Nissan dealer in Springwood QLD in April of 2014. The car was driven a further 1800km since said service. Any ideas would be majorly helpful, failing this i will just eat the bill to take it to someone who knows these cars better than i, however it would be much more favorable to my current position to fix it myself.
PTU/Timing / Leakdown / Earth and fuel pressure need to be checked as well Code 21 ignition can also be a PTU problem indicating the first PTU was having trouble (assuming it was a Series 1 PTU) When you say you replaced the PTU, did you replace it with another S1 PTU or a S2 PTU (hopefully it was with a series 2 as the S1 PTU's can cause miss-firing nightmares just like you mentioned and not necessarily throw a code 21 meaning if you replaced it with another S1 PTU it may have fixed the code 21 but still be another S1 PTU problem as remember the were recalled on the basis that its not whether the S1 PTU will fail but rather when it will fail). Faulty S1 PTU's can cause the trouble you mention - that's all and if you had some slightly improved position after replacing it, its possible that this new PTU may also be sick (just not as sick as the first one hence the code 21) I also agree with checking the timing belt and counting the teeth between each cog to see they are within specs (you could also see if a timing light shows the correct timing as a quick check before moving to the belt itself) Given you have tested everything else so far as you mention, if you haven't worked out the problem by then, I would still do a leak down compression test as a valve could be involved (a problem with a valve / valve seating can sometimes incur similar problems to what your going through) and the leak down will just be another step completed in the diagnosis that you can definitely put behind you. Check the earth connections are secure and also double check the fuel pressure itself by testing Hopefully you will have worked it out by this stage Because it will be a difficult diagnosis if you haven't found it out by the end of these checks Good luck - hope you find the problem soon JC
I will admit it was replaced with another series 1 as thats all that i had on offer at the time. I am currently awaiting a series 2 PTU in the mail and fingers crossed that it solves the issue. If i don't see it turn up before the tech day im hoping someone will be kind enough to lend me theirs for a test at least at the tech day.
Thats sounds promising - you might be laright when the S2 arrives That sound promising then - you might get some luck with an S2 PTU Those S1 PTU's can be a real pain in the arss when they play up because they can be very difficult to diagnose as the problem - especially when they don't give off any code and start making the problem look as if it is somewhere else like the CAS / timing / ECU (and the list goes on). They can be a real pain in the arse to diagnose as most often you end up replacing almost everything/ testing everything before you realise there is nothing else left - LOL Its happened to me before (made me replace/ test almost everything over a long period) - so I hope it turns out to be the problem so you can finally get back to Z free hassles Goodluck :zlove: JC
I had a similar issue with my previous zed. I had issues with it running rough around 2.5k mark which turned out to be a dodgy CAS. I went through a few CAS' until I found a working one. Also the MAF can cause this problem. Best if you know someone with a nicely running zed and willing to swap parts around until you find the problem.
I do have a couple of friends which own Z's and trust me enough to remove parts from thier Z's for testing. I have tested with thier PTU's, with no luck so im pretty confident that its not the PTU. The CAS could be dodgy i guess, but it could be a myraid of other things. If all else fails i will be changing to the LS2/LS7 coilpack setup so i can delete the PTU altogether and i will replace all of the sensors with brand new ones and throw a new timing kit at the car. Failing that, it will be sold and i will walk away from Zed's forever.
If you want to repair the misfire, you need to diagnose what the fault is. You must understand how a system works before you can understand why it isn't working.
