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Discussion Starter · #1 ·
Hey guys,

I just finished the build on the spec V recently, all the details on the mods and maintenance done on it is in the daily thread. It’s got a few kinks though so I thought I’d discuss them with you guys to see if I could straighten them out this weekend when I get back home from work.

So post engine swap, I’ve got two reoccurring check engine light codes. One code is for a misfire on cylinder 4. I installed fuel injectors that I got from 2JR, so I think I can rule that out as an issue. When I get home, I’ll go ahead and swap one of the ignition coils from my old motor onto cylinder 4 and see if that codes is still occurring. If so then I’ll do a compression check to make sure everything is right. I had a random misfire before the engine swap, but it had low compression on all four cylinders, so I believe the wiring harness itself can be ruled out as an issue.
The next code I got is for the variable intake air system since I swapped the cast manifold out for an Altima plenum. This is the only code I was expecting when the swap was finished, but I was hoping that someone would know if there’s an easy way to make this code stay away. Does Uprev have a solution to keep this code turned off? I know with all the different things that I’ve done that it only makes sense to go ahead and get it tuned in the future anyways.
The only other issue I’ve found while driving the car is that there’s a rattling noise coming from the rear end. It almost sounds like there’s hardware or something getting thrown around in the trunk when I go over bumps in the road, but I drove around with the trunk empty and the rattling was still there. I did install polyurethane bushings for the whole rear end, so my theory is that I’m getting more vibrations in the chassis from the stiffer bushings. I don’t know if this is the problem for certain though, so maybe someone else who’s done the same install can chime in. When I get home, I’ll check the torque on all the bolted connections in the rear just to be safe. I also added some hosing from the evap canister so that it can vent outside the bumper, so perhaps it’s just those hoses bouncing around. I also replaced rear struts and everything on the rear brakes, but I really don’t think either one of those are causing the issue.
 

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Discussion Starter · #3 · (Edited)
Check the wiring for the misfire including grounds, plug the the the vacuum solenoid from the old manifold back into the harness that way it clears the code, check the bottom bolts to the strut as well but there is going to be add NVH from the bushings that'll get transmitted.
So cleared the codes and swapped inhibition coils 3 and 4 and the code came back, so I think I can count them out. The spark plugs are also brand new and gapped correctly, so I think it may come down to wiring. What kind of checks can I do for the wiring? I previously added some grounding jumpers from the negative battery terminal to the grounds on the front cover of the engine, and from there to the alternator ground before the motor swap. They raised the voltage level and increased throttle response and fuel efficiency. My best guesses are to check for continuity between the coil plug ground terminal and the chassis ground, and check for 12V at the plug or ignition coil without the engine running.

I also torque checked all the rear end bolted connections and they seemed fine. The car still has vibrations in the rear end which I believe may be coming from the top of the shock tower. Is there supposed to be some gasket material or something between the shock and the chassis? I seem to remember removing some cruddy gasket from the top of the old ones.

Edit: So it seems like the check engine light and codes only come on during cold start. I took the car on a decent 45 minute drive after a warm start and neither of the codes came back. Maybe I’m overthinking it, but it may be that cylinder 4 isn’t getting good voltage and current under cold starting conditions. Almost makes me want to rewire the ignition portion of the wiring harness with larger conductors.
Edit again: I left the A/C and all other electronics turned off to raise the voltage level and started the car again earlier. This time the code that came up was a random misfire instead of a misfire on cylinder 4. I think this is probably more evidence that I should go ahead and upgrade the ignition wiring. The old insulation is probably degraded from the heat of the engine bay.
 

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Discussion Starter · #5 ·
Please update date me on your progress I've been having this exact issue as you have been having on my 05 spec v . Just before it ran hot on me, I'm in the process of doing a complete rebuild and the wiring is the only thing I haven't touched and I'm curious.
Definitely will do. Misfire on cylinder 4 eventually came back again so I ordered a portion of wiring harness from the NissanPartsDeal website which has the ignition coil plugs, knock sensor plugs, etc. I plan on using the new harness portion as sort of a template to figure out how much wire I need to get, then I’ll remove all the 20 ga wiring from the ignition portion of the new harness and add a bigger conductor size and maybe some sort of wrap to protect it from the heat.
 

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Discussion Starter · #7 · (Edited)
I had a similar misfire issue on my 04 Spec after various self-installed mods. I lived with it for over two years worried that I’d done something wrong, but the car pulled hard and healthy otherwise. Some people mentioned removing/ leaving it unbolted and wrapping the knock sensor or something, but instead, I (naively) hoped the issue would be taken care of after I had some head work done (nismo cams and jwt valve springs). Problem persisted. It was driving me crazy so I mentioned it to my uprev tuner and asked if he could get rid of that random cylinder misfire (and later cylinder 4) and he said ‘no problem’. I haven’t had problems or a code since and my car runs great.
Unfortunately, I don’t know exactly what was done or if it was just smoothing out the band that ultimately solved the issue. I vote for a tune!

p.s., I tried aftermarket coils, then purchased 4 new OEM coils, same with spark plugs, ran the colder ones, then went with oem ones. Had car diagnosed by a local shop and Nissan, all they said was “it’s the mods” and took my money.
That’s interesting. I plan on having the car tuned in the future anyways, but I was worried that I would need to make sure my car didn’t have issues before bringing it in or uploading a tune.
I really need to get this new harness in and see how much work it’s going to be to add larger ignition wires. If it’s going to be a pain in the ass to join a new harness portion to the existing one then I may just hold off and try getting a tune first and see if that solves the problem.
The car is behaving a lot like you said, it pulls hard and feels fine driving down the road. Mine seems to have more trouble at startup and idle, which could be due to the mods unrestricting air flow, giving it a leaner air/fuel mixture. The powerband still behaves like I have the old VIAS system intact where the power seems to “wake up” at around 4000 rpm even though I have the Altima plenum now. It probably needs a lot of adjustments from idle up to that point.
 

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Discussion Starter · #8 ·
So a little update here; I’ve been working away from home on business days so I’ve only been working on the Sentra when I have time and energy on the weekends. I installed some racing seats for autocross next year, so I may put up a listing for the Spec V seats soon if anyone’s interested.
Car Vehicle Motor vehicle Hood Steering part


I also decided to be ricey and cut out my fog light to add a velocity stack and pipe to blow air straight at the cold air intake filter. Then I added cool ricer purple lights 🤣.

Wheel Tire Vehicle Car Hood
Car Land vehicle Tire Vehicle Wheel

Automotive lighting Hood Car Purple Lighting

Automotive parking light Tire Car Land vehicle Vehicle

The rear suspension is a fair bit quieter now relative to when everything was freshly installed. My guess is that there’s a break in process for the rubber on the top of the rear strut mounts and they have probably molded to the shape of the chassis at this point.

The car is still having misfiring issues. The wiring harness I ordered came in… I ordered the wrong thing and got the fuel injector harness. It looks like Nissan doesn’t provide other sections of harnesses, so if I want to try to replace wiring then I’ll probably cut out a section from a junkyard car and use it as a template to make my own wiring harness. I’m trying to avoid going this route if I can, so I decided to order the Uprev Tuner package and a Wideband from 2JR to see if the issue can be resolved with a tune. I followed 2JR’s instructions by email and flashed my ECU with a tune they provided, and the car seems to startup easier now, but it’s still struggling at idle and going lean. The wideband will fluctuate around 14.7 for about a minute then it will peak at 16 and 17 for a couple seconds, and the exhaust will start popping at the same time. I recorded video of how my car was behaving before and after flashing the ECU, put it in a YouTube playlist and sent it to them. The guy who was working with me didn’t like what it was doing either, and I’m waiting to see if they have any advice to give me. I’ll share the link here for reference:

https://youtube.com/playlist?list=PLVUKRfUm4Dsx3Thtl4yBbmUlvZWsVLflb

I haven’t tried driving the car around with the flashed tune yet, I want to figure out what my issue is before I take this any further.

Cylinder 4 misfire and random misfire and the check engine codes that are reoccurring. Since the stock O2 sensor is on bank 4 of the exhaust manifold, will the ECU not throw codes for cylinders 1-3? I’m thinking that just because cylinder 4 misfire is the most common code doesn’t mean that cylinder 4 is where the issue is at. Since my spark plugs and fuel injectors are new, I think the next thing to check is all 4 ignition coils just to be certain they’re all good, then ignition wiring to make sure ground terminals have good connection to chassis, and the power terminals have good voltage. I’m also starting to be suspicious of my fuel pump. It would make sense for the air/ratio to sporadically go lean if the fuel pump is on its way out. I also have to assume that the fuel pump is original since I haven’t replaced it myself. 138k miles and 18 years probably hasn’t been too kind to it if that’s the case. I’ll probably order 2JR’s 255lph drop in fuel pump soon just for peace of mind if not anything else.

Once I get the misfire sorted out, I’d also like to see if I can get the car tuned for e85 for a little extra power and because it’s much cheaper than premium gas where I live. Does anyone know what upgrades need to be made to the fuel system to run it, and would the stock size fuel injectors be big enough considering I’m staying naturally aspirated?
 

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Discussion Starter · #10 ·
Don't go E unless you absolutely need to. It's hell on your fuel system. And pretty cost invasive.
I’ll take your word on it. Also a quick google search and fuel injector/horsepower calculator shows that the stock 330’s probably aren’t big enough in the first place so I’ll stick with premium.

I did some diagnosis of the car this morning and these are the notes I took;


Ignition connectors to ground:
All ground terminals are about .3-.6 ohms to battery ground. For reference, other ground points on the chassis or engine to the battery are reading about .2 ohms.

Ignition connector voltage:
Checked voltage on all ignition connectors; all showed 12.6 volts with ignition in “on” position.

Coil pack resistances in ohms:
1 1.752
2 1.741
3 1.717
4 1.708
(Leads shorted together on multimeter shows .2 ohms, so all coil packs may be about 1.5 ohms in reality)

Cylinder compression of all 4 cylinders is 170-180 psi.

Ignition wiring, coils, and compression all look good. The next reasonable thing to check would be fuel pressure, but I don’t have the tool kit for that. I think I’m going to just go ahead and order a fuel pump assembly and see where it goes from there.
 

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Discussion Starter · #15 ·
Ok, I just performed pedal, throttle body, and maf relearns and the car seems much more stable now.

Wideband peak range with AC off at operating temp
13.4-15.8

I ran it at least 5 minutes without the AC off just to give it some time to adjust but it’s pretty hot out here. It seems to stably fluctuate around 14.5-15.1.

Wideband peak range with AC on at operating temp
13.5-15.3

It’s staying stable at 13.8-14.8 much more often with AC on. The idle RPM is less than 1000 with AC on or off, but it’s definitely running smoother with AC on.

I’ve let it idle for at least 15 minutes at this point and it’s a lot more stable post relearn. I cleared the code for cylinder 4 misfire and it hasn’t returned yet.
 

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Discussion Starter · #17 ·
Wait till you drive it.
I got to drive it a bit over this weekend, and I’m really impressed with the car now. With the flash tune, despite not being 100% fine tuned yet, I can already tell a big difference especially at low and mid rpm range. By swapping to the plastic plenum and getting the tune, the car no longer feels like it has discount VTEC where it’ll wait until 4000ish RPM and then give you full power. The power feels really good at low RPM and seems to slowly rise until about 3000 RPM, and then it seems to increase more steeply until the torque levels out at high RPM. At this point the car feels a bit faster than my e85 tuned BRZ with a UEL header, cat-back, and performance filter, but I don’t have any way to prove that other than butt-dyno. The misfire code did come back again, I’m not sure if there’s something I still need to correct or if it’ll get worked out in the tuning process.

I also added an Ultra Racing “rear strut” brace, and it’s made a big difference in the way it handles. I’ve had similar experiences driving the car with the stock front strut tower bar as most other people have shared; the car seems to under steer a bit with it installed. Most guys opt to leave it off and let the chassis flex to get a little more oversteer, but the rear brace seems to have balanced the car by stiffening up the rear end. I feel like I can really whip it through curves and sharp corners with much more precision. I think it definitely gives the BRZ a good run for it’s money there despite being FWD. Definitely need a set of track wheels and tires for autocross later on though. I’m running Michelin Primacy’s on the stock wheels and they’re fine for regular street driving, but I’m afraid of losing traction if push the car much more. I had a laugh with my brother when driving the car earlier today after I stalled at a stoplight trying to be easy on the clutch. I looked at the incoming traffic in the mirror and decided to start then engine, rev up and dump the clutch to get going and all it did was spin wheels and scream at me while we sat there like a couple idiots. It’s a first for me since I’ve never intentionally spun wheels or burnouts or anything like that and I’ve never driven anything without traction control on the street besides the Spec V. It’s cool to see that all the mods are doing their job at preventing wheel hop, but now it’s clear that I need to start shopping for a wheel and tire setup with better traction (and also not drive like an idiot 🤣).
 

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Discussion Starter · #18 ·
I’m still trying to correct the misfire code. I went ahead and got new NGK coil packs, but that hasn’t changed anything.

The misfire seems to happen most often at idle, low RPM, or when letting off the throttle, I’ve begun suspecting that it could be a vacuum leak causing unmetered air to lean out my air fuel mixtures. I replaced the evap purge valve in case, but that doesn’t seem to have changed anything. Maybe the purge valves are directional, as in they’re supposed to flow one way and I may have it backwards? I may try swapping the hoses on it to see if that changes anything. I also trying removing my catch can from my plumbing system and running the hoses in a stock fashion, but that hasn’t changed anything either. I’ve got my PCV and my valve cover vent both going to my catch can inlet, the outlet going to the CIA, and the manifold plugged off. I haven’t messed with the vacuum line going to the brake booster, but the brakes seem to work fine so I’m assuming everything is good there.

I also decided to replace my old fuel pump today. I bought a module for cheap off of eBay, and installed a 2JR 255 lph pump into it. The pump works better, but the fuel level sensor isn’t reading anything. Not sure if I need to remove the module and check it out, or if I can just drive the car around and slosh the bobber or something to make it work. All the wiring looked good right before I installed it. I tried disconnecting the negative battery terminal and reconnecting it to see if resetting the ECU would make it read the fuel sensor but now my dash won’t come on. I always have to wait a night for it to reset when it does this, so I guess I’ll wait until tomorrow to try to keep troubleshooting.

I accidentally ordered a new evap vent valve when looking for the purge valve, so I may install that just to see if it changes anything.
 
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