Hi guys, Just finished a timing belt service on my 91 TT. The car has had some performance work at some stage and was going very well at 10psi. Has the dual stage set at 15psi but never used it. After the service which included underdrive kit, nismo thermostat and platinum spark plugs along with belts/seal etc it is missing/slight hesitation when on boost. Off boost it drives fine. Boost level is as it was, valve timing was triple checked. The only thing I can think of is the spark plugs. It had standard NGK plugs in it. I think the number was bcpr6ey but I have thrown them out now. So I bought the pfr6b-11 plugs which come preset. My concern is the platinum plugs arent working as well under boost as the standard ones were or the 1mm gap is too big? Opinions please. Should I put a new set of standard plugs in it at say 0.8mm and is bcpr6ey the correct number? Any help appreciated.
The platinum plugs are 1.1 gapped at which work perfectly well and are the norm. Plenty of members using them. From the sounds of it, it looks like it's blowing the spark out. But I would first double check all the wiring that goes to the coil packs. Furthermore, what ptu are you using? Series 1 or a series 2? Double check the electrical side of things first as doing a major service as you've done can upset the old looms. Check all the terminal pins and coil pack pins. Etc etc. Failing that then for diagnostic purposes. Throwing $40 worth of coppers at it may be the next best thing. Coppers are used quiet often too, as they're a lot cheaper and work just as well. Just not as long as the platinums though. Let us know how it all goes.
Could be caused by the wiring that has been moved during the work. Check all electrical connections for corrosion, particularly PTU and CAS, but if it is still the original loom then it is also possible that wiring in the loom is broken/corroded. Check also for boost leaks (did they put in new O-rings under the balance tube).
Thanks for the help. We put a set of bkr6e plugs in it and cleaned the MAF sensor. Took it for a drive, after about 2k's it completely dropped 1 cyl and stayed that way. 1 cyl is definitetly not firing. Let it idle and pulled the connections off the coils, they all seem to be working however I cant get to the rear passenger coil without pulling the balance tube off again. So its progressed from a hesition to a miss and is not related to the plugs. Its running a series 1 ptu however it has had modifications to the standard loom at some stage, there seems to be an extra wire going the ptu. ECU shows no error codes. Is it possible an injector has died? Cheers
If you have a multimeter just check the continuity at the plugs. Both on the coil packs and injectors. If they require attention. Do so, clean and file them. This way it will eliminate one possibility. As for a possible dead injector. Seems odd that it's just died now. So for this I would get a 9v battery and put the positive and negative terminals directly onto the injector. Listen for a click. If there is no click. Then yeah it's stuck or dead. Further to this, use thd multimeter if you have one, and check the resistance of the injector. I'll try find the margins for you, for what it should be within. Bringing it back from there, the next thing you can try is swapping over a coil pack with another known working one in the bank. This at least will show if it's a dead coil pack. If all is fine, assume it's good. Further back again, the ptu can usually be the issue. Series 1 units can be fragile. And even circumstances like this they can be happy, then just drop off. Whether it's thd difference in plugs that make it fault, who knows. Do the same here and check the wiring, plugs, terminals. Then still if no go. Give the unit a tap while the engine is running. If it jumps into life, then there is an internal fault. Failing that, try another known working series 1 ptu. Plenty kicking around as most have converted to the series 2 units. At which you can also do as good faith. Another thing to look at after all the above. Check thd cas. Again check the usual suspects. Wiring etc. But also pull it off the camshaft and rotate the driver by hand. I think the key has to be at the "on" position. And this should make the injectors click. Again for another diagnostic. The orings under the balance tube is a good idea too. When i put coppers in my old zed I renewed the orings. Drove it for a week and if developed a hesitating and idle issue. Went through the same ideas as I've written and when i got to taking the balance tube off, the orings had melted. Essentially creating a huge leak. So maybe check yours again. Over and above that. Sounds electrical and will be something so bloody small it will make you laugh and cry when you find it. Haha. Good luck.
Thanks so much for your help. Coil packs check out fine, it seems all cyl are getting spark so will look at injectors next. Will follow your guide and let you know how we go. Thanks again.
Wrong plugs. Those are the NA ones. The TT requires a plug that will extend further into the combustion chamber. The proper plug is the NGK PFR6B-11B. The plugs you got "may" have been pre-gapped to ~ 0.044" but that is supposed to be confirmed with a feeler gauge and not installed directly frm the box. Additionally, it's been common practice to personally change the gap of the PFR6B-11B to 0.035" right from the box. Some even go slightly smaller than 0.035" when running boost in the 18psi and higher range. http://z32.wikispaces.com/Spark+Plug
Thanks mate, we've studied spark plugs to no end. Plugs that came out of it before the service were standard ngk's. So thats what are back in it now.
When you move the looom that reaches across the engine to the PTU, usually connections that have been OK for ages, but are corroded lose continuity. I expect you unscrewed the PTU off the front cam cover and bent it back out of the way leaving the plugs still connected during your 100K service? All this crap is likely because the PTU connections are crap. Pull the plugs and scrape clean the PTU pins with a small file/jewellers screwdriver. Then try to clean the pins inside the connector as good as you can. I expect it will run just fine afterward. BTW the long plugs that where talked about above are US market only. The Jspec plugs are the same reach as the NA ones. So the new plugs you got with the 1.1 mm gap are just fine. Blowing out the spark is only an issue at boost pressures above 18-20 PSI
Thanks tektrader. So we dont run the longreach plugs in the jap specs at all? We removed the ptu from the car altogether while the service was done. Havent tried cleaning its connections yet. We pulled the coils out today and cleaned the terminals and plugs, put new orings on the balance pipes and replaced a few sus looking vaccum lines. Car pulled very well and ran how it was before the service except for about 20seconds. After boosting to 6-7psi through 2nd and 3rd gear a cylinder died while cruising in 4th. After about 20seconds and giving it a bit of throttle all 6 fired again and it ran fine all the way home. So perhaps its heat related and will get worse with longer drives, or Tektrader is right and the ptu is reaking havic with us. Will see how it goes. Thanks again.
You can run them BUT you dont have to. The long reach plugs where used in the NA and TT in the US apparently because of a better burn for California pollution requirements. Normal plugs will be fine. The Jspec plugs for TT and NA are identical I fully expect you will find the PTU has its terminals encrusted with crud you will have to scrape off before it will work. Its a hard calcium like substance that is difficult to remove. I use A jewellers screw driver and scrape it off pin by pin. WASH it with RP7 or similar afterward and lube them with contact grease before you put them back on. $10 says its the PTU
Probably a dumb question - since you appear to be fluent in mechanics. But you stated "since a T-Belt change". So my question is - "did you actually physically count the teeth on the timing belt between the marks as opposed to just lining up the marks" I say that, because I donkied that up once and yu can get all sorts of problems from one tooth out! Regards
Its possible but being one tooth out will make the whole shebang go strange. Not have intermittent cylinder drop outs and alike. Its a noticeable feel and response.
The srvice manual has a diagram and you count the teeth between the timing marks. One tooth out will show a lack of power but NOT cylinder drop outs etc.
Search and you shall find http://www.300zx-twinturbo.com/cgi-...=0&cycle=off&slide=18&design=default&total=70
http://www.ttzd.com/tech/timingbelttech.html http://www.300zxclub.com/showthread.php?t=201046&highlight=count+teeth http://www.300zxclub.com/showthread.php?t=193727 http://www.300zxclub.com/showthread.php?t=194419&highlight=count+teeth http://twinturbo.net/nissan/300zx/f...upplemental-Notes--120k-T-Belt-Servicing.html http://www.ttxtz.com/tech/60k/index.html http://www.twinturbo.net/nissan/300zx/tech/rebuild/rebuild.aspx http://www.300zxclub.com/showthread.php?t=153481 http://www.300zxclub.com/showthread.php?t=194419&highlight=count+teeth&page=3 http://www.300zxclub.com/showthread.php?t=194419&highlight=count+teeth&page=6 http://www.300zxclub.com/showthread.php?t=202536&highlight=count+teeth Hope this helps.
Does it run fine until it warms up? If so it's probably a failed series 1 PTU. They have really fine aluminium wires in them and when one fails it will make contact until it warms up and expands and then the contact will fail. It's a common problem and can happen anytime. It could be just bad luck that it's happened after your service. Cheers, Dave
