240zwannabe Posted September 19, 2007 Share Posted September 19, 2007 ok i did some searching and the closest thing i could find to my problem is this thread here: http://forums.hybridz.org/showthread.php?t=86771&highlight=stutter although, mine is a little different. cold or warm from a start my motor will stutter until about 1775 rpm, it can't be a "not enough fuel issue" because it has just under half a tank in it. sometimes when i start it it will idle at about 1500 and drop to right above 500 rpm, stay there for a while and briefly rev to 1500 again, then drop back to 500. i read in the haynes manual that the lowest recommended idle for a l28 is 800 rpm, is this true? the manual isn't very descriptive when it comes to l28's. it is a 78 l28 with 77 wire harness and a 78 ecu, if thats important... i had this motor running just fine in the original chassis before doing the swap due to a better body. the motor has new injectors, new fuel pump, new fuel filter, 52K miles, new plugs, new wires, new coil, i think thats it. oh yeah, my original thought was bad gas, as the car did sit for 12 years with gas in it, so i drained it for the 2nd time and added new gas. please help me!!! Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted September 20, 2007 Share Posted September 20, 2007 How much fuel you have in your tank is immaterial to what the engine sees. The engine's "to little or too much fuel" depends on fuel pressure and how efficiently the engine utilizes that fuel pressure. How efficiently the enigne utilizes the fuel pressure depends on how properly the FI sensors, ECU, Injectors, Relays, and switches are working with one another. How much of the 77 harness was used? Have you checked fuel line pressure before and after the Fuel Pressure Regulator yet? What kind of miles per gallon are you getting. What do your plugs look like after a few days of engine use? Are all the ground wires getting a clean contact? It is tough to say what your problem is without a detailed methodical diagnosis. Do you have a 78 Factory Service Manual? Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
240zwannabe Posted September 20, 2007 Author Share Posted September 20, 2007 How much fuel you have in your tank is immaterial to what the engine sees. The engine's "to little or too much fuel" depends on fuel pressure and how efficiently the engine utilizes that fuel pressure. How efficiently the enigne utilizes the fuel pressure depends on how properly the FI sensors, ECU, Injectors, Relays, and switches are working with one another. How much of the 77 harness was used? Have you checked fuel line pressure before and after the Fuel Pressure Regulator yet? What kind of miles per gallon are you getting. What do your plugs look like after a few days of engine use? Are all the ground wires getting a clean contact? It is tough to say what your problem is without a detailed methodical diagnosis. Do you have a 78 Factory Service Manual? Kevin, (Yea,Still an Inliner) i stated it not to be another "not another not enough fuel" issue due to it stuttering and sputtering at higher rpm's while i had in running in it's original chassis, sorry i should've clarified that. in the previous chassis i did not have this problem, so i think we can do away with that possibly being the problem. injectors are new. although, i do question the relay, it is still the original relay. i did buy another as my fuel pump will not get power from ignition, so i have it wired through a switch, this also helps with theft protection (i go to school in the "hood"). i am using the entire 77 harness with the exception of the fuel pump wiring and the oil pressure sensor, the 77 and 78 l28's used a different style sensor. MPG is an unknown, i do not have this car completely streetable again, i still have other small things to finish up. i haven't checked fuel pressure anywhere in the lines, i do not have a gauge. i would hope/assume my fuel pressure is just fine everywhere until the FPR, it is also original. i bought a new dizzy rotor and cap today and installed them tonight but it's late and i have work at 8 am and dont get out of school until 10 every night. all grounds seemed to be good when i did the swap. thanks again but please keep the suggestions coming. ps: if the description of my problem isn't clear please ask questions and i will do my best to put them in words Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted September 20, 2007 Share Posted September 20, 2007 i think one thing that would help since you don't know all the variables, is what the plugs look like. they can tell a lot just by the color, as i'm finding out with my car. can you go WOT without any problems till it hits a certian rpm, right off idle? Quote Link to comment Share on other sites More sharing options...
240zwannabe Posted September 21, 2007 Author Share Posted September 21, 2007 i think one thing that would help since you don't know all the variables, is what the plugs look like. they can tell a lot just by the color, as i'm finding out with my car. can you go WOT without any problems till it hits a certian rpm, right off idle? the only time i have to do any work on my car is on weekends, work and school are my life...sucks! i've only revved it to about 5500 rpm but it had no problems getting there after it cleared about 1775 rpm where the stuttering ends, and let me tell you open header l28 is retarded loud! i'll get those plugs out saturday and let you guys know. although tonight i did get home about 10 minutes earlier than usual so i swung by the local walmart and picked up some injector cleaner just to be absolutely sure that wasn't the problem. well, i also plugged the vacuum farthest back closest to the right side of the engine bay. whichever one it was it helped quite a bit although it seems like it's still having a bit of trouble between 1K and 2K rpm, or could this just be the injector cleaner making it run a little awkward? i've never dealt with injector cleaner before this is my first near complete project car (went through 3 different z chassis and 2 engines before coming to a definite choice of the temporary motor while the 3.1 stroker turbo is built). if there is anymore advice without knowing what the plugs look like please keep it coming i appreciate all help. Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted September 21, 2007 Share Posted September 21, 2007 when it stutters, do you mean it's misfiring a bit? cause that's what mine does. i'm not sure which vacuum line you're talking about. I'm pretty new to Z's lol. I think injector cleaner is usually based on jet fuel (at least, my fuel treatment i used to put in my bug was) I suppose you could try what I did. I pulled each plug, and found one that was weaker, but when I revved it to 2k, and let it clear up (it would audibly clear) once i pulled the weak one, it was just as strong as the others, due to the fuel pressure climbing and clearing it. That's how I know it's the problem at least. also, most of my plugs are lean since they can't get enough fuel. (at least, this is what i think the problem is. i won't know till I dig in and clean it all) i'm also wondering, if for some reason your throttle positioning switch isn't adjusted right. but that might not be the problem at all. Quote Link to comment Share on other sites More sharing options...
dj paul Posted September 21, 2007 Share Posted September 21, 2007 dude just bring it over to my house. i live in st. mathews ill fix it for you. i have 3 z's from diff generations and 2 have L28. Quote Link to comment Share on other sites More sharing options...
240zwannabe Posted September 23, 2007 Author Share Posted September 23, 2007 dude just bring it over to my house. i live in st. mathews ill fix it for you. i have 3 z's from diff generations and 2 have L28. see, the problem with that is it's not exactly street legal. plus, it needs more work that just this problem. the hydraulic fluids for some reason wont pump through the slave cylinder, the brakes havent been bled, suspension isnt completely finished, oh dont forget my coolant problem...it wont flow for some reason. ive got an arizona z car radiator on order and should be here within the week. Quote Link to comment Share on other sites More sharing options...
240zwannabe Posted September 24, 2007 Author Share Posted September 24, 2007 alright i finally got time to pull my plugs today...just black. pretty normal looking to me... Quote Link to comment Share on other sites More sharing options...
Guest J-MAC Posted October 9, 2007 Share Posted October 9, 2007 I was driving my 83' 280zx today and it was running fine until about 1 mile down the road. It started sputtering and misfiring, I gave it some gas but no acceleration or rise in rpms. It stalled out, I tried starting it a couple of times with no luck. I looked into my rearview mirror whilst trying to start it and there was a flame coming out of my exhaust. I waited a couple of minutes and tried starting it again, it started right up and ran good. Does anyone know what the cause of this was? Quote Link to comment Share on other sites More sharing options...
240zwannabe Posted October 10, 2007 Author Share Posted October 10, 2007 my 78 z used to do that when it was low on gas. not the shooting flames part but the whole no rise in rpm's or acceleration Quote Link to comment Share on other sites More sharing options...
olie05 Posted October 10, 2007 Share Posted October 10, 2007 Words really can't describe how helpful this PDF was to me when i was running the stock computer. (Actually it helped me with my Megasquirt install too!) Fuel injection bible also, it sounds like an AFM problem to me. Quote Link to comment Share on other sites More sharing options...
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