gexgexgexgex Posted November 23, 2004 Share Posted November 23, 2004 i swaped a 280zxt into my 240 z and loved it. the car was fast, very fast for me. i was running only 7 psi and it was running great. then my fuelpump died. the car would run perfect at idle and run perfect untill i wanted to boost and drive fast. so i put in one of those msd electric fuel pumps. the car still runs perfect at idle, but i still dont have any power. i can rev the car to like 5000 rpm with only like 20% throttle, i am am thinking it has a fuel prob. the car feels like this i hit the gas, and floor it, pulls till like 3000rpm and is making 6 psi boost, all nomal, but then the car like stops making power and like falls on its face slow. and some times a loud poping comes out the back. could it be my stock fule pressure regulator or some other prob. i dont think it is anything like spark b/c i can rev to 5000rpm with no prob as long as i am only like 20% throttle. anything would help Quote Link to comment Share on other sites More sharing options...
Thumper Posted November 23, 2004 Share Posted November 23, 2004 Sounds like spark. Either you have the gap too big, your spark plug is melted, or you don't have enough power going to the spark plug. Reason you can rev to 5k at 20% throttle is because there is not as much pressure inside the combustion chamber. G/L Quote Link to comment Share on other sites More sharing options...
gexgexgexgex Posted November 23, 2004 Author Share Posted November 23, 2004 would my spark plugs just all of a sudden go out. i mean all of them at the same time they look similar to me when i looked at them. by the way what gap should the sparks be at, and are nkg the best Quote Link to comment Share on other sites More sharing options...
Thumper Posted November 23, 2004 Share Posted November 23, 2004 Yes the ngk are the best. Do a search on the spark plugs and you will find what heap range you need for your application and whole lot more info that you should now. But the short answer is a heat range of 6 and a gap from 0.03" to 0.035". Quote Link to comment Share on other sites More sharing options...
Guest Magic Posted November 23, 2004 Share Posted November 23, 2004 I have had the same thing happen on an NA motor when it was placed under load. turned out to be the lead from the coil to the distributor. Quote Link to comment Share on other sites More sharing options...
mjfawke Posted November 23, 2004 Share Posted November 23, 2004 If nothing else changed, I'd be checking the fuel pressure under load. Sometimes those old regulators can't handle a high-pressure/high-flow fuel pump... Either buy a fuel pressure gauge and plumb it into the system temporarily, or hit the local dyno (surely they have fuel pressure gauges?). Find out what the base fuel pressure is supposed to be - under boost, the pressure should rise at the same rate as boost (1:1 rate), so if base is 45psi, you should see 51psi at 6psi boost. Otherwise, the new pump might be drawing a lot of current and dropping the voltage to the coil... or you could have a bad lead. A bad lead/coil tends to cause misfire under load... but it's kind of obvious when the spark goes as it's pretty violent! Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted November 23, 2004 Share Posted November 23, 2004 Try unplugging and plugging in the ECU a few times. I had a similar issue and that cured it. It may just be a bad contact.... Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted November 23, 2004 Share Posted November 23, 2004 First of all congrats on completing the swap! Second of all, how many times has this been said? Check your AFM, ECU, TPS connectors. Disconnect them, clean with electrical contact cleaner, smear some di-electric grease on the blades and reassemble. Better than 80% of the time, that is the problem.....TRY IT. Quote Link to comment Share on other sites More sharing options...
Cody 82 ZXT Posted November 23, 2004 Share Posted November 23, 2004 Another thing that it sounds like to me is the stock knock sensor. It can pull a ton of timing out and make the car feek like that. Is it still hooked up? At stock boost with good gas it really shouldn't be doing anything but, if the tune is off then it might be. Check your plugs and connections then verify your timing. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted November 23, 2004 Share Posted November 23, 2004 Yep... ALWAYS make checking/cleaning your wiring harness connectors the first thing to do with odd problems like this. These are the exact same symptoms experienced by myself, Cygnus, and quite a few other guys here, and when all we did was disconnect and clean the connections at the ECU, AFM, and sensors, all was well afterwards. I also used the dielectric grease on ALL my connections the last time I had to clean them, and have not had to touch them since. That was about ... 3-4 mos. ago if I remember right? Used to be the car would start running crappy on boost, every 2 weeks to a month and I'd have to clean everything. The new pump could be overwhelming the FPR, but I'd think it'd be much more noticeable off boost than on. When I upgraded to an MSD pump, using the tiny tiny stock 240z return line, fuel pressure was way up, like 80psi. It ran very rough and bogged badly, smoking and backfiring, under normal driving, then when I'd floor it, it'd bog and choke and once full boost came on then suddenly it would just GO. Ran fantastic once boost hit, so I'm doubting that's the problem for you. Quote Link to comment Share on other sites More sharing options...
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