KnightoftheRound Posted December 3, 2009 Share Posted December 3, 2009 Hey all, unfortunately this is my first post. A little background on my car, it is an 82, with an 81 L28ET swap: I completed the Z31 ECU swap 2 weeks ago according to the writeup by Ashfin. ECU is a Remanned one from an 85 Z31T. The car idled great till it warmed up, and then it started sputtering HARD. From total cold, to the heavy sputtering, its only a couple minutes. Blipping the throttle will made it stumble and then go back to sputtering, holding the throttle down at all will kill it. It idles less than 500 rpm, barely. It ran perfectly with the 81 ECCS before the swap. Things I have done and checked include: New Nissan CHTS, checked harness continuity, both component and harness pass. New Nissan o2 sensor for an 81 L28ET, verified that it was giving voltage while the car was on, gave a steady .3ish volts. TPS is from an 83 NA if it matters. Has continuity at throttle closed, no continuity after slightly open. Checked harness. Tried 4 different MAFs, tested EVERY ONE against FSM tests, all check out. Current one on car is from a known well running car, along with the ECU. I had to have rechecked all the Z31 swap wiring 10+ times, and I see no error. Fuel pressure stays steady and never drops once warmed up (it actually goes up, due to bad vacuum from horrible idle) Unplugging the CHTS causes the idle to go smooth out and run fairly well. Car will not start without CHTS plugged in (as its supposed to, IIRC). CAS disk is in the correct oreintation, and is almost mirror clean with no debris or scratches. Tried 2 different CAS units, one from a perfectly running Z31T, and one from the 83 dizzy I am using. Timing is set at 20 BTDC. Checked harness grounds, at the grounds, and at the ECU plugs. Air regulator is working properly, and shuts once warmed up, it is also a new Nissan unit. Coil and Power transistor are from an 87 Z31. The only real running code the car has is a code 11, CAS, not really sure what to make of it, as the car ran perfectly fine before the swap. I don't have another ECU to try =/ I have been battling this thing for 2 weeks now, and I am getting very close to just breaking down and swapping the old 81 flappy box and ECU back. My problem is frighteningly similar to this Zcar.com post, on this guys 85 Turbo Z. http://www.zcar.com/forums/read/2/2022915/2022925#msg-2022925 but it was never resolved that I have seen. If anyone can provide any help or insight, maybe something I might have missed, I will love you forever. Quote Link to comment Share on other sites More sharing options...
Mikez31ss Posted December 3, 2009 Share Posted December 3, 2009 This may be totally unrelated but you say it's fine until the motor warms up? I can give you some insights into it from a z31 perspective. When the motor warms up the ecu goes into closed loop. The o2 sensor begins to play the major role in feedback. A rule of thumb in the z31 world is to always match your o2 sensor to your ecu. Maybe the L28 o2 sensor isn't playing nice with the 85t ecu? Then again maybe when yall do this z31 ecu swap you have some workaround for that. This is something I'm interested in. Using a z31 ecu in an L28et swap in a 240z would be great. Nistune Quote Link to comment Share on other sites More sharing options...
GrayZee Posted December 3, 2009 Share Posted December 3, 2009 I had a phantom problem with mine a long time ago. I could never figure it out, after trying a ton of other things I finally ripped the harness out and made a new one from scratch. That fixed the problem 100% Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 3, 2009 Share Posted December 3, 2009 Unplug the o2 sensor, adjust the throttle stop on the throttle body to get the car to idle 8-900 rpm. Check the tps for adjustment, it should go open about 200rpm above idle. Make sure all the idle and emission controls are disconnected as they won't work with the z31 ecu, and that all vac lines that have been disconnected are plugged. Erase the cas code and see if it pops up again. Quote Link to comment Share on other sites More sharing options...
KnightoftheRound Posted December 3, 2009 Author Share Posted December 3, 2009 Didn't really help, just made it idle like crap at a slightly higher RPM. TPS seems to be working, it has no continuity once you ever so slightly give it throttle, and has continuity when its not being touched. Not sure if there is any more to it than that. All emissions stuff, and the VCM was removed long before this swap. All vac nipples that are not in use are capped with zipties tight around the caps. Going to try to get a video of it, my phones camera is good, but the audio is bad. Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 3, 2009 Share Posted December 3, 2009 what do the sparkplugs look like? and make sure not to plug that o2 sensor back in.. Quote Link to comment Share on other sites More sharing options...
KnightoftheRound Posted December 3, 2009 Author Share Posted December 3, 2009 All the plugs look like this more or less: Video, sorry for the bad audio, the G1 can take nice pics, but a camcorder it is not. Car sounds like my dads turbo diesel Isuzu Trooper.... Quote Link to comment Share on other sites More sharing options...
Bernardd Posted December 3, 2009 Share Posted December 3, 2009 Try new plugs, have you checked the continuity from the plug to the ecu from the maf/cas/chts? When you checked the timing was the engine fully warmed up, tps closed or shorted? Or did leave it alone form the stock efi setting? I see the engine is an 81, did you swap to the 82-83 cas setup? Quote Link to comment Share on other sites More sharing options...
KnightoftheRound Posted December 3, 2009 Author Share Posted December 3, 2009 Those WERE new plugs. Yes, I have checked for continuity in the CHTS harness, CAS harness, MAF harness, TPS harness, and O2 (now disconnected) harness. None of those harness's, save for the MAF harness, were touched from the old setup which ran perfect. I rechecked the MAF harness today from the plug to ECU with an 84 Z31 diagram, there are no faults with it. I went to a local Z yard here, and tried an 86T computer, and an 84T computer, both had the same results. About to go out and RE-RE-RE-check all the damned harnesses again, this is so frustrating. FWIW, the switched 12v source for the MAF, I used one of the b/w VCM wires. For the switched 12v source for the Fuel Pump relay, I believe I used a wire from some connector that looks like -| hanging under the dash near the silver cylinder shaped thing that works the turn signals and such. Quote Link to comment Share on other sites More sharing options...
KnightoftheRound Posted December 3, 2009 Author Share Posted December 3, 2009 Scratch everything I said in this post. Update: My dad has been telling me the whole time that the injector voltage is wrong, for the past 2 weeks... he suggested putting the dropping resistors back on to see how it runs with them.... Well, I slapped the dropping resistor pack back on, and you know what? It ****ing runs perfect, I have no explaination as to WHY it runs perfect with the resistors in place, but it does. I don't want to look at that car the rest of the night, ugh. Quote Link to comment Share on other sites More sharing options...
luvmy280zxt Posted December 4, 2009 Share Posted December 4, 2009 So how does it drive? Pretty sweet i bet. You shoud do a write up on how you did it. If you have time away from driving it! Quote Link to comment Share on other sites More sharing options...
woldson Posted December 4, 2009 Share Posted December 4, 2009 It's all good;) Nice troubleshooting, just think of how much more familiar you are with your setup! Quote Link to comment Share on other sites More sharing options...
Mikez31ss Posted December 4, 2009 Share Posted December 4, 2009 Scratch everything I said in this post. Update: My dad has been telling me the whole time that the injector voltage is wrong, for the past 2 weeks... he suggested putting the dropping resistors back on to see how it runs with them.... Well, I slapped the dropping resistor pack back on, and you know what? It ****ing runs perfect, I have no explaination as to WHY it runs perfect with the resistors in place, but it does. I don't want to look at that car the rest of the night, ugh. Cool. Bet you have high impedance injectors. Quote Link to comment Share on other sites More sharing options...
KnightoftheRound Posted December 5, 2009 Author Share Posted December 5, 2009 Adjusted timing, set TPS, drove it today, and boy does it run good now. Hauls ass. Not as much as my other Z, but still hauls ass. That warning 280ZTurbo made in his "supplement" to Ashfin's write up is true, I guess I can say I experienced it first hand. After I realized that it wasn't the wire the fans were using as a + source, and realized that its whatever field/signal the fans make when on, I played with it a little bit. I took the intake piping off the front of the MAF, and pushed it closer to the fan motor while the car was running, and it started running REALLY choppy. I pulled it away, and it gradually got less choppy as I got farther away from the motor. Weird stuff! Consider this case closed. Quote Link to comment Share on other sites More sharing options...
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