Thread: Slight missing throughout throttle?

I cant really figure this out. I was having low fuel pressure, and I fixed that. I've been having this slight missing through the whole power band. Kinda like it's a lil bumpy/jerky while I'm giving it gas at all times. Also when I punch it from idle it will hesitate really bad, and get real jerky feeling like it's missing. When it hits around 2-2.5k it revs freely, but still a lil bumpy. The only known code is for the knock sensor, so it's running a lil rich. I believe that's in my harness. Going to replace it tomorrow. Any ideas though?

Ok. I replaced the knock sensor harness and still have the code. IDK what to do about this? Very confusing. I'm going to have to test the ecu harness I suppose. I'm still getting that missing, but it's more like a sputtering though. I can feel it while accelerating, and it still does it if I floor it from idle. It will slowly rev and sputter real bad until it gets to around 2k+ then revs freely while still sputtering slightly. So any ideas guys? Thanks for any help. It's very much appreciated.

Also sometimes it will stall when I push the clutch in to stop at a light, or if the radiator fans kick in at idle and put a load on the alternator.

have you done a normal tune up lately? how old is the fuel filter/spark plugs/wire/dist. cap/rotor/etc....?

give it a seafoam treatment.

did you run the car the car out of gas shortly before it started? that can make it suck up crap and plug the fuel filter.

you could try cleaning the maf sensor, or have you tried cleaninng that yet? also what are your plugs gapped to?

OEM cap and rotor installed a week ago. 300ZX TT fuel filter over the weekend. Swapped out fuel pump and regulator few days ago. Put in spark plugs and wires around last july. Less than 2K on them as of now. The plugs are NGK Iridium. Cant remember the heat range or code. Don't know the gap, but they aren't supposed to be regapped because the needle point I believe. Wires are those fat red ones from advance auto. I regrounded the MAF long time ago. Swapped out for another 1 the other day as well and cleaned it. Tested the voltage on it and it's reading perfect. I tested all of my circuits per the FSM for power and ground system and all is well. Tested the knock sensor also and the wire harness has continuity and the sensor is brand new. I have had the knock code 34 since I got this car with the old engine and also this new one I just swapped in. Even 3 diff ECUs. I can't for the life of me figure out WTF is the deal with this thing. I spliced in a new KS harness as well. I didn't have the sputtering with the old engine that had 210K on it. This low port I swapped in does though. I believe the timing chain tensioner was bad because the chain was ticking on the top chain guide(Removed last night as well). So, I swapped it out for the one from my old High port. The old one was the old style, but had more tension than the new style one from my lowport with half the mileage on it. Haven't had a chance to run it since I swapped them last night because I Put some copper RTV on my DP gasket. I will crank her up in a little while and see if it made a difference. If it does I'll order a new tensioner. I also swapped distributors because of the crank sensor code I had and that fixed it. For some reason when I did my last swap with the highport it wouldn't start. That engine came from a manual 93NX and went into my (at the time) auto 92NX. I think maybe because some of the manual sensors I used on that engine it was confusing the auto ecu and wouldn't allow the inhibit relay to click. So I spliced into the ignition signal wire and ran it straight to the starter solenoid to bypass it. I always had to feather the gas to start it. I now know why. The ECU never saw neutral so It couldn't start properly. Over the weekend I rewired it correctly and just tied the neutral harness wires together for now since both my reverse and neutral switch are bad and I cant get them out. Even on my new swap I had to feather it to start, But since rewiring it the correct way, The manual ecu sees neutral and it fires right up.

I swapped out the TPS and IACV from my old low port to my new high port earlier. It seems to have helped a little. So we will see if it stayes that way, lol.

so swapping out the tps and iacv helped? you arnet getting the slight miss throughout the powerband

I meant to say high port to low port, but yes it did help somewhat. It isn't as bad, but is still there a little bit. I set the idle and timing close to 18-19 deg. It actually went into timing mode this time. So, to sum it up its still there ever so slightly and hesitates if I give it gas real fast. I just don't know what else to try really.

well thats good that its somewhat fixed. you reset the tps when you put the newer one on right?