Connor280ZX Posted July 10, 2013 Share Posted July 10, 2013 I've had my Z for about a year and it has always had this cold start problem. I've acctually thought it was normal for and old car, but it just doesn't seem right. Heres what it's doing. Upon cold start up, turns over just fine with no excess cranking. If i try to even give it the slightest amount of throttle while cold, the engine stumbles and backfires. It won't pick up RPM at all. Sometimes, if i give it more than 1/5 throttle when its cold, it will nearly stall for a sec (RPM drops below 500 for spit second until pedal is released) I have to wait for the cars temp to reach at least 120 before its pretty much drivable. Starts to run normal at around 140. Heres what i've replaced involving the engine management system: -CHTS -IAC -O2 Sensor Car has roughly 65,000 Miles. Quote Link to comment Share on other sites More sharing options...
Heroez Posted July 11, 2013 Share Posted July 11, 2013 That is likely why the FSM and says not to rev the motor unnecessarily untill it reaches operating temp. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted July 11, 2013 Author Share Posted July 11, 2013 I'm not trying to race the engine while its cold, I'm just trying to get it to acctually drive when it's cold because I prefer not to sit in the car for 10 minutes letting it idle before its drivable. I like to hop in my car and go to work as soon as I turn the key. I would highly doubt that Nissan designed this car in a way that it would be nearly impossible to drive unless it sits and idles for 10 minutes. The point I'm trying to get across here is that there has to be a problem with something in the engine management system that is NOT allowing the engine to run right. Quote Link to comment Share on other sites More sharing options...
ctc Posted July 11, 2013 Share Posted July 11, 2013 Have you run the troubleshooting procedures in the FSM or are you shot gunning parts? Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted July 12, 2013 Author Share Posted July 12, 2013 I've practically had to replace every single sensor/ ETC Unit on this car since i've bought it, in order for it to run right. Even had 31 Yr old tranny fluid when i bought it. So i had my car over at a Datsun specialist's shop today to get the Parking brake cables replaced, and i was discussing this issue with him. I mentioned that when i had to replace the Dist. cap and rotor, that i found a ball bearing and plastic debris under the rotor. He says repace it immediately because a major timing/vac advance component has broken inside of it, which is causing improper vaccum and timing when the car is cold. So, I'm going to buy a new Dist. and post the results when i replace it. I'll upload a pic of the old one so you can see how trashed it looks inside. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted July 19, 2013 Author Share Posted July 19, 2013 Ok so i got the new Dizzy in today. Installation went just fine, everything lined up and all, timed the ignition to 5 degrees. Went for a test drive, noticed less low end acceleration power, and as the RPMs climb, all of the sudden the thing just starts sputtering and backfiring, and will not rev past 4500-5000 RPM. Revving in neutral, it runs just fine. Checked all my connections again which seem fine. I am at a complete loss here. Completley dumbfounded on why this is happening. I've replaced practically everything in the EMS except for the ECU... Quote Link to comment Share on other sites More sharing options...
ctc Posted July 19, 2013 Share Posted July 19, 2013 Have you check the resistance on the AFM for a dead spot? What about vacuum leaks? Quote Link to comment Share on other sites More sharing options...
Domzs Posted July 19, 2013 Share Posted July 19, 2013 Strange . If the car was running fine ( warmed up ) before you replaced the dist. , I'd go back and double check your work or could be bad new dist. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted July 19, 2013 Author Share Posted July 19, 2013 Have you check the resistance on the AFM for a dead spot? What about vacuum leaks? Vaccum lines are all intact, did a test and seems to be no leaking. When i sent the car in a few weeks ago to get new E brake cables installed, i had him check the AFM because i thought that was my problem here, but he says its fine... Strange . If the car was running fine ( warmed up ) before you replaced the dist. , I'd go back and double check your work or could be bad new dist. That would be my only logical guess. All the connectors are secure and intact, vaccum advance is connected tightly, and i re timed it. I mean unless something else just happened to go out coincedently, then my guess would be a bad Dist... Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 19, 2013 Share Posted July 19, 2013 Ok so i got the new Dizzy in today. Installation went just fine, everything lined up and all, timed the ignition to 5 degrees. Went for a test drive, noticed less low end acceleration power, and as the RPMs climb, all of the sudden the thing just starts sputtering and backfiring, and will not rev past 4500-5000 RPM. Revving in neutral, it runs just fine. Checked all my connections again which seem fine. I am at a complete loss here. Completley dumbfounded on why this is happening. I've replaced practically everything in the EMS except for the ECU... Did the new distributor fix the original, cold start (warm up) problem, or do you have a new problem in addition? Two problems now, or one new one? Have you tested the TVS (throttle valve switch, aka TPS, page EFEC-56) ? The ECU uses it to know if the throttle is at idle, mid, or full throttle. Your two problems seem to fit a TPS issue. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted July 19, 2013 Author Share Posted July 19, 2013 It still cuts out when cold, idles smoother. TPS is brand new as of last week. Pretty much two problems now. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 19, 2013 Share Posted July 19, 2013 Do the TPS test at the ECU. Take the plug off, identify the TPS pins and do the test. See what the ECU sees. Then you'll know for sure. New parts may not be communicating properly. Actually, at this point, sitting by the ECU plug with the FSM and a multimeter could find you a solution. At least you can be more confident it's not electrical and spend your time looking at the mechanical things like the various vacuum valves. One off-the-beaten-path possibility is a corroded EGR passage or stuck EGR valve. Full time EGR might cause your symptoms. Doing the ECU tests at the ECU first makes sense though. It's tedious but you'll probably find some things that aren't quite right. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted July 19, 2013 Author Share Posted July 19, 2013 Ok, I guess I could do a test... How exactly do I perform this test? Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 19, 2013 Share Posted July 19, 2013 Start at the link below. You can print the EFEC pages for your Datsun specialist or get a multimeter and do the testing yourself. Good luck. http://www.nicoclub.com/FSM/ Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted July 20, 2013 Author Share Posted July 20, 2013 I investigated the new distributor more by swapping out parts from the old one to see if it would make any difference. Sure enough, I swapped out the ICMs and now the car runs great. Faulty ICM that came with the new dizzy. As far as the cold start problem goes, well, I'll find out once I drive it again. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted July 24, 2013 Author Share Posted July 24, 2013 Car now starts up and will run when cold. Guess it was all due to the bad dizzy. Did a compression test while I was at it. 186-182-184-184-182-180. Very happy with those results since factory spec is 170. Quote Link to comment Share on other sites More sharing options...
whyfeel Posted August 3, 2013 Share Posted August 3, 2013 That's great compression. I noticed you set it to 5 degrees BTDC. FSM calls for 8 plus/minus 2 degrees BTDC for an '82. I run 10 BTDC on my '82 zx with a '79 engine. Also double check the head temp sensor. I clean mine every few months to be sure, because it directly correlates to your fuel mixture. I know the hesitation and stumbling you are talking about. The car will run great but sometimes when cold it falls on it's face and starts "popping" in the intake somewhere until you let off the throttle. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted August 3, 2013 Author Share Posted August 3, 2013 That's great compression. I noticed you set it to 5 degrees BTDC. FSM calls for 8 plus/minus 2 degrees BTDC for an '82. I run 10 BTDC on my '82 zx with a '79 engine. Also double check the head temp sensor. I clean mine every few months to be sure, because it directly correlates to your fuel mixture. I know the hesitation and stumbling you are talking about. The car will run great but sometimes when cold it falls on it's face and starts "popping" in the intake somewhere until you let off the throttle. I originally had my timing set for 9 BTDC, however it began to idle rougher than usual, so i set it back to 5... Not sure why... And yes, the popping and stumble, thats exactly what it does! Still does it after the dizzy change, but not as much... Thats interesting becuase i replaced the CHTS about 1,500 months prior to this... Also, i am still expirencing a slight rough idle, maybe a 100-120 rpm variation (used to be 150-180 rpm). I'm starting to think that this is just the way the car was made to run... I mean the only other thing i could imagine causing this rough running is the Vacuum switch, or the ECU... Any insight on this? Quote Link to comment Share on other sites More sharing options...
Swervey McZCar Posted August 12, 2013 Share Posted August 12, 2013 It is often the ECU. Use your diagnostic decision tree in the FSM. Been here, done this. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted August 12, 2013 Author Share Posted August 12, 2013 I've taken my car to the datsun guys shop to have him do a whole bunch of tests on the ECU a few weeks ago and he says that everyghing is checking out fine. What about vacuum? Maybe something like a switch, or valve isn't working right. Quote Link to comment Share on other sites More sharing options...
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