Kingnothing616 Posted November 9, 2008 Share Posted November 9, 2008 Although this is my first post, I am not new to the site, and any help would be greatly appreciated. After searching for a while I finally figured I should post my exact problems. I have a 76 280z that I bought back in may as my first z car. 55k original miles and it had no compression on #3, so I found a rebuilt motor that i couldnt pass up and dropped it in about a month ago. I ran it for a couple weeks with an extreme loss of power, and finally got around to doing some diagnosis. Not hitting on #3 or #4. Good enough spark, within 2 or 3 deg. on timing, 125 compression on all cyl. Pretty sure it got rebuilt with new turbo pistons. Good Noid on all injector wires, so I figured bad injectors. Found some NISMO new injectors from a guy in california, and put them in on friday afternoon with new rubber.. etc. Now I am hitting on all 6, but it runs like crap. seems to have a dead miss at exactly 1600, no more no less, and it will not rev past 3500 without bucking, and just straight up running terrible. So I did all the simple stuff before it got frustrated.. new cap and rotor, checked and regapped plugs, checked timing, etc. I am somewhat at a loss, I dont know if the flowrate of the new injectors is too much, or if it is ignition or what. I mechanic for a living, and am a quick learner i just need to know where to start. Thanks a lot.... Coye. Quote Link to comment Share on other sites More sharing options...
smoorhs02 Posted November 9, 2008 Share Posted November 9, 2008 coil perhaps? vac leak? i sorta have this same issue on my 78...regarding the bucking and crappy rev. she will hesitate and frontfire right above idle but after about 3200 or so she takes off like a jet. have u cleaned all electrical connectors on the harness? i have yet to do this because the whole rearend is ripped apart, and about to get put back together with new suspension and bushings. if you havent checked the coil check that, and for vac leaks, then clean all electrical connectors, then find the FI bible and do all the diagnostic checks. and check fuel pressure. supposed to be around 36psi...hope this helps. jeremy ps - where is mineola, tx at? im in arlington, between dallas and ft. worth. if youre local maybe we could me up sometime. Quote Link to comment Share on other sites More sharing options...
Kingnothing616 Posted November 9, 2008 Author Share Posted November 9, 2008 I have checked for vaccum leaks, and I have a blaster 2 coil on the way just for kicks. I checked all of the electrical connectors on the fuel injectors before i hooked them back up, but not some of the others yet. Mineola is about 90 miles east of you on Highway 80. I go through where you live all the time on I-30 to go see my sister in Saginaw. Also was wondering what wires i should go with, I know Magnecors are good, but ive been looking at the ngk blues as well.... Quote Link to comment Share on other sites More sharing options...
woldson Posted November 10, 2008 Share Posted November 10, 2008 55K on a 76? Fuel filter? Get a fuel pressure gauge. Quote Link to comment Share on other sites More sharing options...
Kingnothing616 Posted November 10, 2008 Author Share Posted November 10, 2008 I just put a fuel filter on it a couple weeks ago just for maintenence. Im thinking its either a sensor, or lack of hot spark problem, because when i cranked her up this morning there is black smoke pouring out when i rev it up. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted November 10, 2008 Share Posted November 10, 2008 OK... couple things to check. First question, does it smoke? Like blue smoke from way to rich? Anyhow, Kingnothing616: your issue sounds a little like throttle position sensor. Which is not a sensor at all, it's more like two sets of contact switches. The cover on it will pop right off. Check it out with the engine not running, work the throttle and watch the contact switches. One set of contacts should be closed when the throttle is closed completely and open a little off idle. Then there should be a portion of throttle travel when both sets are open and then about 3/4 open or so the second set should close. Under no circumstance should both be closed at once. If they aren't working like this bend them around until they do. Next thing is the water temp sensor. smoorhs02: this really sounds like your issue. When the water temp sensor goes bad, the system goes full rich, idle is horrible / non-existent and the motor only cleans up up high. This sensor is a universal type part and readily available at any parts store for around 15$. Cheap diagnoistics. But Kingnothing616, before looking at any of this, check every connection in the system. The fuel injection wiring harness is a whole separate harness and it only has around a dozen connectors. Take each one apart, spray some electrical contact cleaner in there, give a little scrubbing with an old toothbrush and another good blast of contact cleaner. Doesn't matter if the car only has 55K miles on it, it is still thirty years old and these things have not the greatest wiring harnesses. If the connector on the water temp sensor is really bad, just replace it, it's the same as the one on the injectors and they make a little kit to replace them. If the injectors you replaced have a higher flow rate then the stock injectors the fuel ratio is going to be wacked out. You can adjust the ratio by fiddleing with the AFM but I don't know if you will be able to get enough adjustment. If you decide to try find Blue's tip on Zcar.com or Atlanta Zcar club web site. Also might want to check the carbon trace on the AFM. Requires a volt meter. Again check Blues tips. But first eye ball it, sometimes a big chuck of the trace just falls right off. DOWNLOAD THE EFI BIBLE from link at top of this forum. DO IT.... NOW! read it, read it again. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted November 10, 2008 Share Posted November 10, 2008 ... because when i cranked her up this morning there is black smoke pouring out when i rev it up. a-HA ... water temp sensor! Quote Link to comment Share on other sites More sharing options...
Kingnothing616 Posted November 12, 2008 Author Share Posted November 12, 2008 Well I was really busy at work today, so i only got to tinker with it for about 10 minutes at the end of the day. I started taking the connectors off of the water temp sensors, and everything that i have found, and searched for shows that there should only be three. Well my 280 has four. Anyways i cleaned all of the connectors and hooked everything back up, could be my imagination, but it seems like its not smoking quite as bad, and it still will not go one lick past 3500 without missing and running like crap. Just an update, still need to check the TPS contacts, etc. Thanks for everyones help. Quote Link to comment Share on other sites More sharing options...
iaconsultants Posted November 20, 2008 Share Posted November 20, 2008 Just a thought take the Distributer cap off and the rotor off. There is a Star like element on the shaft of the distibuter and an electronic pick up that looks like an opened up thick L shaped piece of plastic with some wires coming out. If the gap between there is too much you will get a strange stumbling action when you increase the RPMs. Do not use a steel feeler gauge on this but use a brass one. I do not remember the gap but some 10 years ago I bought a Z that someone had actually pushed the palstic pick up too close to the stator (star shaped element) and ate away at the stator. Check to make sure there is no foreign build up and that the teeth are all in tact. Hope this helps/ Quote Link to comment Share on other sites More sharing options...
Kingnothing616 Posted November 20, 2008 Author Share Posted November 20, 2008 I will definately check that and some other things today. Last night i finally had a chance to tinker with it again. I have not had my multimeter out yet to check resistance on the coolant temp sensors, but i did double check all of the connectors everywhere, and everything is suprisingly clean. I took apart the TPS, and at about the 2k rpm spot, both of the contacts were touching, so i pulled another tps i had off another motor, and it does the same thing, but per momsz's post i bent the contacts around to about where i thought that they should be, and also put some new NGK blue wires on there. It seems to be quite a bit better, its not just flooding itself out like it was, and it will rev like crazy w/o being in gear. But as soon as you take it down the road and give it more than half throttle it starts bucking, and missing. The rpms can be at 2k or 4k, as long as you get there slowly its fine, but as soon as you give it more than half throttle it goes nutso. I know I still have some more checking to do, so here is an update, and any input is always greatly appreciated. Thanks, Coye.... Quote Link to comment Share on other sites More sharing options...
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