S15 surging with lean condition - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Ice77 · 05-28-2021, 07:28 PM

So... here goes,
I have an S15 sr20det in my s14. I have a gt2871r, 740 HKS injectors, 340 lph aeromotive fuel pump, mspnp2 for s13 with wires moved around to correspond properly through a wiring specialties patch harness, maf not used only the four bar internal map in the mspnp and tuned in late January and dyno?d at 336 whp. All supporting Mods (don?t know if it?s needed to include all the little stuff too) for those upgrades as well. Last week I changed the oil at around 8-9 at night was dark do I was using lights. After I changed the oil I started it and it was miss firing, after some checking found it was cylinder 1 miss firing. I have changed the coil packs to the packs from the VQ35DE. I have multiple packs since I bought some after markets from O?Reilly and pulled 6 from a couple of VQ35DE?s from the junk yard (after the tuner told me I should use some factory ones) I changed it and miss fire stopped. The car ran perrrrrrrfect for a long while after the tune, now after the oil change it?s surging at idle and running pretty lean I have checked every thing in case I knocked something off or broke a wire in the harness. I have smoke tested everything for vacuum leaks and boost leaks every thing is sealed and golden and even found a ground wire that was ripped out, after chasing it down found it ran to a plug that isn?t even used in my application. I?m banging my head against the wall but can?t find anything off or wrong. There should be no reason for it to be surging and running lean as I literally did not do anything except change the oil, is there anything I could have hit or knocked off around the oil filter that I?m missing that could cause that kind of issue?

My! · 05-28-2021, 08:49 PM

potentially could be a failed tps sensor?

Ice77 · 05-28-2021, 09:02 PM

TPS is reading perfectly on the dashboard for megasquirt, but I?ll check it out based on fsm tomorrow. Appreciate the feedback

mechanicalmoron · 05-30-2021, 12:33 PM

Considering you did an oil change, did you do a long enough smoke test that you would have seen a loose oil cap?

Ice77 · 05-30-2021, 03:31 PM

TPS if functioning according to spec. I also watched a video where someone had a leaky cap so I did go back and double check that before I posted. But I wasn?t home and when I first saw it I thought to myself ?dude if you left the cap loose you better not tell anyone?. But I also did 2 to long smoke tests completely filled the system where it came out of the intake filter

Ice77 · 06-16-2021, 05:10 PM

Well seems it was something with the tune, how it changed without me hooking up the laptop is beyond me. Checked everything, new tuner told me it sounded like an issue with the tune so I brought it in. He tuned it again and so far seems to be running fine. It?s raining like hell now so I can?t ?feel? if it is different other than it is idling better than it has since I put the motor in the car even before any of the upgraded pieces. Hope this helps anyone who might have the same issue

05-28-2021, 07:28 PM	#1
Ice77 Join Date: Jun 2018 Location: Florida Age: 43 Posts: 11 Trader Rating: (0) Feedback Score: 0 reviews	S15 surging with lean condition So... here goes, I have an S15 sr20det in my s14. I have a gt2871r, 740 HKS injectors, 340 lph aeromotive fuel pump, mspnp2 for s13 with wires moved around to correspond properly through a wiring specialties patch harness, maf not used only the four bar internal map in the mspnp and tuned in late January and dyno?d at 336 whp. All supporting Mods (don?t know if it?s needed to include all the little stuff too) for those upgrades as well. Last week I changed the oil at around 8-9 at night was dark do I was using lights. After I changed the oil I started it and it was miss firing, after some checking found it was cylinder 1 miss firing. I have changed the coil packs to the packs from the VQ35DE. I have multiple packs since I bought some after markets from O?Reilly and pulled 6 from a couple of VQ35DE?s from the junk yard (after the tuner told me I should use some factory ones) I changed it and miss fire stopped. The car ran perrrrrrrfect for a long while after the tune, now after the oil change it?s surging at idle and running pretty lean I have checked every thing in case I knocked something off or broke a wire in the harness. I have smoke tested everything for vacuum leaks and boost leaks every thing is sealed and golden and even found a ground wire that was ripped out, after chasing it down found it ran to a plug that isn?t even used in my application. I?m banging my head against the wall but can?t find anything off or wrong. There should be no reason for it to be surging and running lean as I literally did not do anything except change the oil, is there anything I could have hit or knocked off around the oil filter that I?m missing that could cause that kind of issue?

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

05-28-2021, 08:49 PM	#2
My! Zilvia Member Join Date: Mar 2010 Location: fort worth Posts: 152 Trader Rating: (8) Feedback Score: 8 reviews	potentially could be a failed tps sensor?

05-28-2021, 09:02 PM	#3
Ice77 Join Date: Jun 2018 Location: Florida Age: 43 Posts: 11 Trader Rating: (0) Feedback Score: 0 reviews	TPS is reading perfectly on the dashboard for megasquirt, but I?ll check it out based on fsm tomorrow. Appreciate the feedback

05-30-2021, 12:33 PM	#4
mechanicalmoron Zilvia FREAK! Join Date: Jul 2013 Location: tx Posts: 1,072 Trader Rating: (0) Feedback Score: 0 reviews	Considering you did an oil change, did you do a long enough smoke test that you would have seen a loose oil cap?

05-30-2021, 03:31 PM	#5
Ice77 Join Date: Jun 2018 Location: Florida Age: 43 Posts: 11 Trader Rating: (0) Feedback Score: 0 reviews	TPS if functioning according to spec. I also watched a video where someone had a leaky cap so I did go back and double check that before I posted. But I wasn?t home and when I first saw it I thought to myself ?dude if you left the cap loose you better not tell anyone?. But I also did 2 to long smoke tests completely filled the system where it came out of the intake filter

06-16-2021, 05:10 PM	#6
Ice77 Join Date: Jun 2018 Location: Florida Age: 43 Posts: 11 Trader Rating: (0) Feedback Score: 0 reviews	Well seems it was something with the tune, how it changed without me hooking up the laptop is beyond me. Checked everything, new tuner told me it sounded like an issue with the tune so I brought it in. He tuned it again and so far seems to be running fine. It?s raining like hell now so I can?t ?feel? if it is different other than it is idling better than it has since I put the motor in the car even before any of the upgraded pieces. Hope this helps anyone who might have the same issue