Guest 2slo4u Posted July 29, 2004 Share Posted July 29, 2004 Well I completed the 280 to 300zx ecu swap the day before yesterday and I am overall satisfied with the swap. I'm amazed it even works and now the rpms will go up to 7000 and bounce! I still have two problems to deal with before adding an intercooler (I have a mazda i/c I am hoping to modify the inlet and outlet). -Car hesitates at beginning of acceleration, with a/c on it seems worse(adjusted tps aok) -Still has missing at idle and it's erratic miss, has no pattern. Anyone have any ideas? The head is supposed to be in good shape after I got the valves ground and seals replaced. The timing chain is right on and timing using a timing light is right on also. New plugs and wires also.????????? 81zxz31turbo? 95slobaru impreza Quote Link to comment Share on other sites More sharing options...
Bernardd Posted July 29, 2004 Share Posted July 29, 2004 I had the same thing when I first swapped. Firstly what do your plugs look like? Sounds like you're running lean. It could be a vacuum leak or you need to adjust the maf. There's a plug on the side of it similiar to the afm on the l28et. Try that or raising fuel pressure a little. Bernard Quote Link to comment Share on other sites More sharing options...
Guest 2slo4u Posted July 29, 2004 Share Posted July 29, 2004 Yeah, it's probably some kind of vacumm leak. I haven't had a chance to pressurize everything to check for leaks. I hope it's not on the bottom of the intake manifold gasket. I'd never find it. I'm going to block off the egr and aac valves in the morning and change the pcv even though it looks really clean. The car had the same miss before the swap over. I hope there is no valve or cam or spring problem. I might even take the cam and rockers from my other head so I can make sure all clearances are parallel and even. The guy who did the valve job said he didn't put the rockers back in the same places. He said it didn't matter. I think he might be wrong. Thanks, Bernardd 81zxturbo 95 slobaru impreza Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 29, 2004 Share Posted July 29, 2004 I've had a misfire problem on my car ever since doing the turbo swap. I have checked and quadruple checked and there are NO vacuum leaks. I have checked and changed all kinds of things. The motor has been rebuilt from top to bottom. Every part of the ignition has been replaced. I've changed over to a '75 intake manifold, so dont have any of the smog crap on there any more. Nothing changed. I am almost POSITIVE that it is dirty or clogged injectors. A few guys on here have also pinned that as a most likely cause... the fuel not getting atomized enough, left over fuel droplets getting thrown out the exhaust and combusting causing my pop pop pop... makes sense to me. I haven't been sure if I should remove them and send them for cleaning... as I've been going back and forth with the idea of upgrading to bigger injectors, but considering I've done just about everything else to try to eliminate this problem, I'm 99% sure if I swap them out or have them cleaned, the problem will go away. If not, then I also suspect the possible cam issues.... though I've adjusted the valve clearances and checked them a few times.... I know the head shop that rebuilt my head also did not label the rockers and install them in their original places, even after I told him to... last time he'll get my business. Funny you mentioned about that... I've always kinda suspsected that in the back of my head as well, even though no one here has considered it a possibility. Quote Link to comment Share on other sites More sharing options...
Guest 2slo4u Posted July 29, 2004 Share Posted July 29, 2004 My injectors are brand new turbo injectors. I'm pretty sure they are ok. That leaves vacumm leaks or cam issues I guess. 81zxturbo 95slobaru impreza Quote Link to comment Share on other sites More sharing options...
jgkurz Posted July 30, 2004 Share Posted July 30, 2004 I've had slight miss at idle on every turbo Z I've owned. My current Z has a standalone ECU with all new parts and it still has the annoying miss. The last resort I thought about trying was to buy a set of Magnacor wires. Maybe it's just the way the L6 burns the fuel at idle. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted July 30, 2004 Share Posted July 30, 2004 You might want to make sure that all spark plug wires wind up crossing each other if ant two run parallel, causing an 'inductance misfire'. Something often overlooked or forgotten.... Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 30, 2004 Share Posted July 30, 2004 Brad-ManQ45 - okay... um... exactly what do you mean? *electrically stupid here* Got a pic to show exactly what you mean?? I replaced my wires with new NGK wires... other than making sure they were in the right order on the cap, I didn't arrange them any particular way... maybe this is the cause of my problems? Here is a pic of how mine are arranged... did I do it wrong? hopefully you can see in that pic if they are arranged right or not... would be really great if it was something simple and stupid to fix like just rearranging my wires. Quote Link to comment Share on other sites More sharing options...
jgkurz Posted July 30, 2004 Share Posted July 30, 2004 The interesting thing here is that this seems to be a common problem. bastaad525 obviously has his new wires arranged perfectly or as Nissan did from the factory. My wires are also secured with plastic seperators and neatly arranged. Although our wires are new and our cars make the expected power the wires may still be the culprit. This is a total guess on my part, but after reading the Magnacor website I thought it was worth checking out. If you go to Maganacor's website they pretty much say thay everyone except them will have problems with (EMI) Electromagnetic interference. http://www.magnecor.com/ Quote Link to comment Share on other sites More sharing options...
Guest 2slo4u Posted July 31, 2004 Share Posted July 31, 2004 I don't believe that stock high resistance wires can induct to the other wires, at least when they are in good shape. Solid core wires on the other hand (unless they have a braided ground shield for each individual wire) might have possible inductance. I don't really believe this to be the problem as a new Nissan would not have done it, and if so, wouldn't everyone know about it by now? Has anyone out there owned a turbo 280zx brand new that could tell us if theirs did this when new? 81zxturbo(quicker every day) 95slobaru impreza Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 31, 2004 Share Posted July 31, 2004 One other reason I do believe it might be a cam/rocker arm issue is because the misfiring does seem to fluctuate with the temp that the motor is running at... There seems to almost be a 'sweet spot' in the temp where the motor will run the most smooth, with little or no misfire at all. When cold it misfires the worst, then as it warms up it cleans up, but then if I get on it a lot and temps climb, or if it's just a particularly hot day, it will start to get worse again. Of course I have checked and adjusted the valves when the car was hot. it is odd, I too have heard of quite a few guys with L28ET's having this sort of thing happening. Some have suggested it's inherent to the ET's low low compression.... Quote Link to comment Share on other sites More sharing options...
Guest 2slo4u Posted July 31, 2004 Share Posted July 31, 2004 I have checked with a timing light and notice that sometimes when the car misses, the cylinder I have the pickup cable on does not fire. You can put it on any spark plug wire and wait... you'll notice it won't fire every time. You guys check yours like that and let us know what happens. Maybe it's some type of ignition problem. I have two extra coils from other zx's I am going to try out. I don't think it's the ecu or the distributor sensor because those have been changed. 81zxturbo 95slobaru impreza Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted July 31, 2004 Share Posted July 31, 2004 I used to notice erratic sparking, waaaay back when I first did the turbo swap. Not sure what I did to get rid of it but it's not there anymore. Sometimes I do notice when there is a misfire while watching the timing, the timing mark will jump a few degrees... never really thought much of it. ALL components of my ignition have been replaced. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted July 31, 2004 Share Posted July 31, 2004 When was the last time you changed out the cap and rotor? All my ZX's have done what your descibing from time to time. Seems to me like it happens more when the ignition componets are less than new. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted August 4, 2004 Share Posted August 4, 2004 If any two wires run parallel (right next) to each other and do not cross over one another (make an 'x') there is the possibility of an inductance misfire. Sorry - no pics, but my description says it all. Quote Link to comment Share on other sites More sharing options...
Guest Cronic Posted August 4, 2004 Share Posted August 4, 2004 Ignition or fuel. I know you said you replaced everything on the ignition side, but it happens. Dizzy is usually the culprit of misses at idle, also bad plugs, dirty/bad injectors, etc. Something with ignition or fuel delivery is fubar. Another thing that can cause this, and has already been covered is vacuum leaks. They're notorious on old motors, with 20 year old lines... such as mine. The vacuum leak will cause the fuel delivery to be wacky and unpredictable since the maf reads a specific amount of air, and if that air isnt in the combustion chamber when the spark fires.... all kinds of annoying things happen. Hope that helps some. I know it's vague, but it's hard to get specific about this kind of issue. Quote Link to comment Share on other sites More sharing options...
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