Connor280ZX Posted January 18, 2013 Share Posted January 18, 2013 For about a few weeks or so, ive been dealing with this odd misfire problem with my car. When its warmed up, it misfires under slight acceleration, idle, and deceleration. The odd thing is that once the engine rpms rise above 2300-2500 or so, the misfire dissapears. I just replaced the PCV valve, and got the ignition timed. Cap, rotor, plugs plug wires and fuel filter have all been replaced a few months prior. I went through most of the vaccum lines, and they all seem in good shape. No cracking or splitting. Any ideas on what might be causing the problem? Quote Link to comment Share on other sites More sharing options...
ArchetypeDatsun Posted January 18, 2013 Share Posted January 18, 2013 Have you checked your exhaust/manifold gasket? Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 18, 2013 Share Posted January 18, 2013 Sounds lean. I would measure fuel pressure before getting too carried away. If it's right, look harder for vacuum leaks, including the EGR system. Download the FSM and read Engine Fuel... chapter to get a good understanding of the EFI system. Might not solve your problem, but it will help you in the long run. In future posts, tell what year car you have, how long you've had it and whether or not it's stock. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted January 19, 2013 Author Share Posted January 19, 2013 Thanks for the replies. Checked the manifold/exhaust gasket and it seems fine, however i forgot to mention that my car is in need of a valve adjustment. Im not sure if clackity valves would cause it to be misfiring. The year of my car is 1982, its naturally aspirated, and has 62,538 miles. The only upgrades are an MSA Catback exhaust with a Summit Racing muffler, and a Crane PS20 ignition coil. *Update* I just started up the car after returning home and i was shocked at what i saw. The second i fired it up, it started to idle very rough, and low around 300-500 rpm. After about 5-10 seconds, the car died, but the fuel pump continued to run for a few seconds. I started it up again and it ran just fine for some reason. I actually happened to be making a video of the car at the same time. Please see the video attached. http://www.youtube.com/watch?v=LG19nULM8OA Quote Link to comment Share on other sites More sharing options...
Josh280z Posted January 19, 2013 Share Posted January 19, 2013 (edited) EDIT: disregard Edited January 19, 2013 by Josh280z Quote Link to comment Share on other sites More sharing options...
SDgoods Posted January 23, 2013 Share Posted January 23, 2013 How do your plugs look after driving like this? You should be able to tell if its running rich/lean and should guide you to the next step. Also has the 02 sensor ever been replaced? Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted January 23, 2013 Author Share Posted January 23, 2013 That's a very good idea to check the plugs. As far as I know, the o2 sensor is original. That will be the next step I'm going to take to try and resolve this issue. Quote Link to comment Share on other sites More sharing options...
nismosilvia Posted January 25, 2013 Share Posted January 25, 2013 Replace all fuel injector/ fuel management connector with the newer style plugs found on newer vw jettas etc. My 78 810 had a bad stuttered around 2:5k changed those and feels like a different engine. also you might wanna look at the thermostat and the sensors in that area while your at it. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted January 30, 2013 Author Share Posted January 30, 2013 Update: I went ahead and bought a new o2 sensor, installed it, and now 90% of the misfire has gone away . As far as the other 10% goes, i think it will completely go away once i adjust the valves. I found out that my EGR valve has a very slight leak, so i will be replacing that soon as well. Quote Link to comment Share on other sites More sharing options...
wadenelson Posted May 30, 2013 Share Posted May 30, 2013 Replace the plugs with NGK's and MAKE SURE THE GAP IS CORRECT! Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted May 30, 2013 Author Share Posted May 30, 2013 Replaced plugs with NGK when I bought the car 6 months prior and gapped at 043 Quote Link to comment Share on other sites More sharing options...
wadenelson Posted May 31, 2013 Share Posted May 31, 2013 Very unlikely an 02 sensor is responsible for the symptoms you describe nor would replacing it correct them. Have you put a vacuum gauge on it? A vacuum leak is a lot more likely cause. Quote Link to comment Share on other sites More sharing options...
Connor280ZX Posted May 31, 2013 Author Share Posted May 31, 2013 haven't personally checked the vaccum with a gauge, but I did send the car in to get the vaccum tested and system inspected and according to the guy who worked on it, everything checks out fine. Quote Link to comment Share on other sites More sharing options...
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