Car runs fine but misfires randomly for short time - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

JayGriffy · 08-09-2018, 11:52 AM

Hey guys, first post here

S15 sr, brand new 750cc, z32 maf, spitfire coils, new plugs.

Car runs fine and I'm running 20-22 pounds right now. On my old setup I was having the same problem where I'll just be driving around, no problems, and bam I'm on 3 cylinders for a couple seconds and then it's gone. Would this be a sign of a coil going bad? I was playing with my Greddy Profec last night so I was able to catch a glimpse of afr when it happened. Once it was a little richer, once it was a lot leaner(when it started misfiring) but I find it hard to believe it's my injectors as I got a new harness when I bought the injectors. Any info would be much appreciated

Kingtal0n · 08-10-2018, 11:34 AM

I had this happen to a couple cars and it was usally the injectors, injector plugs,

or the wires at the computer.

car 1. the engine would run on 3-cylinders when you twisted/jiggled the ECU. Found out one of the pins in the "brand new wiring specialties" harness wasn't making a good connection. Shoved some bits of wire in the hole and good since then.

car 2. Would drop a cylinder sometimes after a bump. turns out the fuel injector plugs weren't really seating well. They were mis manufactured. I had to replace all of them (on a V8 engine) to get it to stop

car 3. fresh engine just installed ran on 3-cylinders. Again it was the injector plugs. cheap injector plugs.

car 4. started misfiring at idle. then gradually got worse and misfired while driving. It was the plug wires, arcing to the head.

car 5. Would misfire at idle and high boost even with a decent gap. The plugs had only 8k on them and looked "ok" but a new set of plugs cleared up 90% of the misfire. Still it misfired though with coppers sometimes. Put some iridiums in and that completely fixed it (supra 2jz). I only put iridiums in the 2jz now.

08-09-2018, 11:52 AM	#1
JayGriffy Join Date: Aug 2018 Location: WA Age: 27 Posts: 1 Trader Rating: (0) Feedback Score: 0 reviews	Car runs fine but misfires randomly for short time Hey guys, first post here S15 sr, brand new 750cc, z32 maf, spitfire coils, new plugs. Car runs fine and I'm running 20-22 pounds right now. On my old setup I was having the same problem where I'll just be driving around, no problems, and bam I'm on 3 cylinders for a couple seconds and then it's gone. Would this be a sign of a coil going bad? I was playing with my Greddy Profec last night so I was able to catch a glimpse of afr when it happened. Once it was a little richer, once it was a lot leaner(when it started misfiring) but I find it hard to believe it's my injectors as I got a new harness when I bought the injectors. Any info would be much appreciated

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08-10-2018, 11:34 AM	#2
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 40 Posts: 4,828 Trader Rating: (17) Feedback Score: 17 reviews	I had this happen to a couple cars and it was usally the injectors, injector plugs, or the wires at the computer. car 1. the engine would run on 3-cylinders when you twisted/jiggled the ECU. Found out one of the pins in the "brand new wiring specialties" harness wasn't making a good connection. Shoved some bits of wire in the hole and good since then. car 2. Would drop a cylinder sometimes after a bump. turns out the fuel injector plugs weren't really seating well. They were mis manufactured. I had to replace all of them (on a V8 engine) to get it to stop car 3. fresh engine just installed ran on 3-cylinders. Again it was the injector plugs. cheap injector plugs. car 4. started misfiring at idle. then gradually got worse and misfired while driving. It was the plug wires, arcing to the head. car 5. Would misfire at idle and high boost even with a decent gap. The plugs had only 8k on them and looked "ok" but a new set of plugs cleared up 90% of the misfire. Still it misfired though with coppers sometimes. Put some iridiums in and that completely fixed it (supra 2jz). I only put iridiums in the 2jz now.