Pilgrim Posted May 8, 2007 Share Posted May 8, 2007 Recently my '83 ZXT started stumbling and missing about 3500 RPM. The problem went away but came back and is now persistent. It doesn't feel like ignition, and I've done fuel injectors, plugs, cap, wires and rotor in the last 1000 miles. My first thought was fuel filter - although I changed it a couple of years ago. Changed it again, and no joy - still missing. I noticed that when I pulled the line off the fuel filter, there was NO spurt of fuel. I'm thinking the fuel pump should have left that line pressurized. I'm thinking bad fuel pump. I guess maybe it's worth changing them every 24 years or so! Any comments? Quote Link to comment Share on other sites More sharing options...
so_icey84 Posted May 8, 2007 Share Posted May 8, 2007 I had this same problem on my 280zx N/A and I changed everything you changed as well as the fuel pump and nothing then I changed the coil and that fixed the problem but if you want measure the coil with an ohmeter and also check all vacuum lines make sure they're not cracked or damaged. Quote Link to comment Share on other sites More sharing options...
sweetleaf Posted May 8, 2007 Share Posted May 8, 2007 Test your fuel pressure.. Quote Link to comment Share on other sites More sharing options...
Pilgrim Posted May 9, 2007 Author Share Posted May 9, 2007 Test your fuel pressure.. That's what I'm a-thinkin'. At least it's not hard to do. NAPA gets about $141 for a replacement...haven't checked Nissan parts options yet. But I'm interested in other comments as well..... Quote Link to comment Share on other sites More sharing options...
turboboost Posted May 9, 2007 Share Posted May 9, 2007 Here's what I think is your best bet. Take your fuel filter off, and get a buddy to start the car. (Make sure you have some rags around the area.) If a whole bunch of gas comes squirting out, then its not your fuel pump. If it is your fuel pump, head out to your local junkyard and look for basically any electrical fuel pump. Basically one from any fuel injected car should work, and you could probably get it for about 15-20 bucks. Quote Link to comment Share on other sites More sharing options...
george.bryant Posted May 9, 2007 Share Posted May 9, 2007 I had exactly the same problem for 3 weeks. Took a while to figure out. It was the Ignition Coil Module (Switch). Get another one and swap them over and see if that helps:-) Quote Link to comment Share on other sites More sharing options...
Daeron Posted May 10, 2007 Share Posted May 10, 2007 at around 3500 RPM?? stumbling? does the urbo have the same style throttle position switch? I know that on my 75 NA stocker, any time i got a drop of water under the hood the TPS went schizo and the engine REFUED to go above 3500RPM. I punch the gas, it revs freely up to 3500 then just.. poof... until the needle dipped back down to below 3 grand, then vroom.. poof.... vroom, poof... Might be worth investigating, the TPS is basically a three position switch.. Idle, cruise, and WOT. if your WOT contact is poor then you would have the problem you are mentioning. Of course, my mouth may be writing an invitation to my foot, since I do not know what kind of TPS the turbos used, but hey.. I'm just tryin to help. If I am wrong, hopefully someone will correct me so I will know not to say this next time. Quote Link to comment Share on other sites More sharing options...
Pilgrim Posted May 14, 2007 Author Share Posted May 14, 2007 I've had the problem with the TPS getting wet when washing the motor - boy, will THAT kill your revs at @3500. But I think it's fuel delivery - just haven't had a chance to get under it yet. Quote Link to comment Share on other sites More sharing options...
(goldfish) Posted May 15, 2007 Share Posted May 15, 2007 Quickly check the ECU connector. Quote Link to comment Share on other sites More sharing options...
COmputoman Posted May 31, 2007 Share Posted May 31, 2007 Ive had the same issue happening with my NA 1982 280zx. After letting the car sit for a few hours, then attempt to start the engine and take off, upon hitting the gas my engine will seem to be cutting in and out of actually igniting. Just replaced 3 of the small vacume lines.... not fixed. Once the engine builds up pressure the issue dissapears quickly. Also one of the injectors seems to have gas leaking onto the outside. I will post pics soon, also I will try replacing the coil. Would it be wise to replace the coil with a proformance coil with the rest of the engine stock? im thinking about doing more upgrades to the engine, but dont really know where to start. Quote Link to comment Share on other sites More sharing options...
Pilgrim Posted June 2, 2007 Author Share Posted June 2, 2007 Computoman, I don't think there's any point in replacing the coil until you have eliminated gas as the problem. Your symptoms don't sound like electrical issues to me. I had an '82 280ZX that would die suddenly - it was the ignition module on the side of the distrib that got hot and failed - typical problem. Easy to diagnose, too. Carry a thermos of ice water - when the engine dies, coast to the shoulder, pop the hood, douse the ignition module on the dist side with icewater. If you can fire it right up after this, you know hte problem. At any rate, I borrowed a fuel pressure gauge from a mechanic friend and will test the pump's output this weekend. Bet I find there's not much pressure coming from the pump. Quote Link to comment Share on other sites More sharing options...
280zx_sliding Posted June 2, 2007 Share Posted June 2, 2007 well ive had a similar problem. whenever i am am WOT it cuts at about 4500 rpm. my car is a 1981 280zx with a dual su swap. i had the stumbling problem since i lost the gas cap. im thinking not having a gas cap does not allow pressure to build up and thats where im losing it. ive changed coils with an msd blaster and a accel super stock. both have the same problem. ive doe all kinds of tunning with the carbs still nothing. anyone have an idea of what it could be for me? Quote Link to comment Share on other sites More sharing options...
george.bryant Posted June 2, 2007 Share Posted June 2, 2007 :icon50:ok. For the third time now "IGNITION COIL MODULE"!!!!!!!!!!!!!!!!!!!!!!!!!!!! Quote Link to comment Share on other sites More sharing options...
Pilgrim Posted June 3, 2007 Author Share Posted June 3, 2007 :icon50:ok. For the third time now "IGNITION COIL MODULE"!!!!!!!!!!!!!!!!!!!!!!!!!!!! George, I'll double-check, but on the turbo model I didn't think there was such a module. (I may not have made it very obvious in my original post listing it as a "ZXT", but it's a turbo.) I'll research it today. I know there's no ignition module on the side of the ditributor like there is on the NA models, but now that I've re-read your posts, I think you're referring to a different part. Yesterday I checked fuel pressure and it's 60 PSI, so there's no problem there. However, the throttle position switch had badly corroded connectors and I treated them with DeOxit to cut through that. Took the car out and drove it, and it worked great. I'm very suspicious, but I'm thinking it COULD have been corroded contacts on the TPS. I know that if you get that TPS wet, your ignition will cut ott about 3K RPM. More later..... Later: Can't find any reference to an ignition coil module, but there is a "Power Transistor" mounted on the side of the bracket that holds the coil. Is that what you're referring to? And BTW - took the Z out for another run after cleaning the TPS contacts and no stumbling or faltering at high revs. Quote Link to comment Share on other sites More sharing options...
Pilgrim Posted June 6, 2007 Author Share Posted June 6, 2007 Well, after cleaning and using DeoxIT on the throttle position sensor, I've driven the car for two days without any sputtering or hesitation. Once again, that silly little TPS turns out to be the answer to a seemingly major problem. But I'm grateful not to be out $150 for a fuel pump. Caig Labs sells DeoxIT and other great contact cleaning and preserving chemicals like ProGold. GREAT stuff, not cheap, but worth every penny. Keep some around. Quote Link to comment Share on other sites More sharing options...
COmputoman Posted June 6, 2007 Share Posted June 6, 2007 Where is the throttle Possistion sensor located? Quote Link to comment Share on other sites More sharing options...
280zx_sliding Posted June 6, 2007 Share Posted June 6, 2007 ya well i am carbed so the tps dosnt matter. maybe since its not hooked up to anything and i still have my ecu hooked up. i took off my ignition control module and tested it and it passed 9 times out of 9. and i cleaned it off and all of thew connections. so does anyone have any idea what it could be. also do u know what i can do about removing the ecu? i went carb and the only thing i really need to run is the dizzy/coil Quote Link to comment Share on other sites More sharing options...
spacecase70 Posted June 7, 2007 Share Posted June 7, 2007 the tps is located on the left side of the throttle body it is the black box with three wires going into it and has 2 screws holding it to the TB Quote Link to comment Share on other sites More sharing options...
280zx_sliding Posted June 7, 2007 Share Posted June 7, 2007 ya i know that but i am carbed now. im runnin dual su carbs. and the carbs have no tps. so i need to figure out how to wire up the coil and dizzy without using the ecu. or is it already a separate wiring harness. edit: sorry didnt see you were talkin to computo Quote Link to comment Share on other sites More sharing options...
spacecase70 Posted June 8, 2007 Share Posted June 8, 2007 ya i know that but i am carbed now. im runnin dual su carbs. and the carbs have no tps. so i need to figure out how to wire up the coil and dizzy without using the ecu. or is it already a separate wiring harness. edit: sorry didnt see you were talkin to computo no problem you can use your stock ignition system is a stand alone w/ seperate harness Quote Link to comment Share on other sites More sharing options...
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