DuoWing Posted June 25, 2009 Share Posted June 25, 2009 Alright, here's a question for you guys. A while back when I got my Z31 I was having hard start and stumble at cold startups. The car would generally run fine once warm. The ECU was putting out code 21. I ended up replacing the Ignition, Coil, Wires, Plugs, etc. Seemed to be really no different. Then I was eventually getting code 13. So I put in a new CHTS and that actually did help. The car runs pretty well, I also replaced the sub harness for the CHTS. Anyway under boost or more throttle I have no issues. Under steady driving with little throttle it feels like there's a slight miss or a slight stumble, it's not really bad, but slightly annoying. After driving for a while I rechecked the ECU codes and still only had code 21. Any thoughts on this? Also I tried to pay attention, at first I thought it was only at 2000RPM when it happened, but it seems like I can stay in a lower gear at higher RPM and still get the same issue. I'm thinking possibly TPS? I'll have to check it, maybe it's improperly adjusted and I'm sitting with my pedal right at the point where it switches on or off. Quote Link to comment Share on other sites More sharing options...
DeleriousZ Posted June 25, 2009 Share Posted June 25, 2009 some codes like to hang around for a while, try clearing the codes from the ecu by selecting diagnostic procedure 4 after 3 is selected, or disconnecting the battery for a while. Check the connection on your fuel temperature sensor. I had a slight buck/burble/miss/whatever when the connection to the FTS was corroded and crappy. It was a very very light condition, hardly noticeable but it was there. Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted June 27, 2009 Share Posted June 27, 2009 tps won't cause miss or stumble it just changes the fuel/air ratio slightly at idle. in your replacing etc up there did it include new dizzy cap and rotor. Had the same on my 85 and that cleared it up. Running 9.5 psi boost Quote Link to comment Share on other sites More sharing options...
Zdaddy Posted June 30, 2009 Share Posted June 30, 2009 The old miss and stumble on my Z31 turned out to be an injector recall botch job. The miss turned into 3 cylinders on one side not firing at all (Car still ran though! Long live the first Japanese V6!) The injector harness was crimped really poorly and basically fell apart in my hands when I inspected it. Fixed that and my VG rand smooth as I never experienced before! Quote Link to comment Share on other sites More sharing options...
DuoWing Posted July 5, 2009 Author Share Posted July 5, 2009 Yeah, I forgot to mention when I did change everything I went all out. New plugs, NGK wires, cap, rotor, coil, ic unit, chts, chts sub harness. I reset my ignition timing just slightly advanced, but that was before I changed over the plugs and plug wires as well as the CHTS. I should recheck my ignition timing. I'm not sure if my Z31 has had the injector recall done to it or not. I'll have to take a closer look. Quote Link to comment Share on other sites More sharing options...
DuoWing Posted September 1, 2009 Author Share Posted September 1, 2009 Well a quick update, I recently did an oil change, put a new fuel filter in, reset the ignition timing, advanced it a little. Going to put it back to normal when I put my NIStune ECU in. Anyway it was still basically doing the same problem, missing at light to little throttle, but seems to run generally fine in upper RPMs and higher throttle. Need to recheck ECU codes since it's been awhile, but I only ever get 21. I pulled the connector off my TPS as I've been meaning to check that today and the contacts are completely green and corroded so tomorrow when I have time I'm going to clean them up. Also I was trying to OHM them out and I was getting nothing, so it looks like the TPS is also improperly set or dead. So I'll pull it, clean up the contacts, check to see if it still works, adjust it, and then install my K&N cone filter and go for a drive. Quote Link to comment Share on other sites More sharing options...
DeleriousZ Posted September 1, 2009 Share Posted September 1, 2009 What plugs are you using and what are they gapped to? Quote Link to comment Share on other sites More sharing options...
DuoWing Posted September 2, 2009 Author Share Posted September 2, 2009 I want to say NGKBPR6ES or something along that line, I think gapped to .44 As far as my TPS goes, I think it might be on it's way out. I put the multimeter prongs on it and the ohm reading is jumping all over the place. Quote Link to comment Share on other sites More sharing options...
DeleriousZ Posted September 2, 2009 Share Posted September 2, 2009 Try closing the gap to .40, and those are the correct plugs IIRC. NGK Coppers are the way to go! Quote Link to comment Share on other sites More sharing options...
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