Working out the kinks on the fresh build

CrickiKaze said:

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.

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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.

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.


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 🤣.




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?

Tritton said:

Don't go E unless you absolutely need to. It's hell on your fuel system. And pretty cost invasive.

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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.

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.

CrickiKaze said:

Wait till you drive it.

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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 🤣).

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.

Ok I feel like an idiot, but it’s getting better.

August was a hell of an infuriating month trying to fix the misfire issue. I’ve been working away from home 12 hours a day, 6 days a week; so I’ve been trying to make the best out of my free time when I get it. In reality, I really just rushed things and beat my head against a wall.

One of the first things I did to try to fix the misfire issue last month was order some new NGK coil packs. They arrived when I was away from home so I asked my younger brother to go ahead and install them to see if anything would change. What I found out later on when going to check spark plug gaps was that he overtightened the coil pack bolts to the valve cover to the point where the rivet nuts locked to the bolts and spun freely so that I could no longer remove the coil packs without removing the valve cover. 🤦‍♂️

I removed that 255 lph fuel pump about 3-4 times trying to fix that fuel level issue, and I had ordered another o-ring gasket every time I got it wrong. The o-ring expands when you unseal the pump from the tank, so you really need to pay attention to the pictures of fuel pump modules to make sure you attach the bobber correctly the first time. I took some of the time waiting for o-rings to be delivered to diagnose what could be causing the misfire. I decided to cut back the tape over the ignition coil wires to make sure nothing was frayed or shorted anywhere. I eventually put more tape back on the wires later on to protect them from the heat, but this whole deal would come back to kick me in the teeth later on so keep this part in mind when you read the rest of rhis.

When I finally resolved the fuel level issue, my wideband sensor was showing that the car was idling and running super lean; worse than it performed before the pump replacement. At this point the car had started backfiring into the intake if I blipped the throttle while sitting, and the car would severely limit the power when trying to take it on the road. I figured that either there may have been something else I overlooked when installing the pump or I may have had a vacuum leak somewhere. I ordered another new fuel pump, stock flow this time, and a new evap canister to compliment the new vent and purge valves I ordered previously. I installed the new goodies and still nothing changed. I bought a smoke machine and meticulously checked for leaks and never came up with anything. I took the car for a drive to autozone to buy a gas cap and see how it’d behave. Although it was running lean according to the wideband gauge, it appeared to be dumping fuel to try and compensate because I was getting 3-4 miles to the gallon and my fuel tank level was dropping dramatically compared to how it ran earlier this summer. At this point, I figured this had to be something timing related, or somehow an issue with the maf sensor and ecu not adjusting correctly. I ordered NTK cam and crank sensors, maf sensor, and another new valve cover so that I could finally get around to getting my coil packs off.

I got back home from this evening today and the new parts were all here waiting for me to install. The old maf sensor screws came off incredibly easy, so I think I had either not tightened them well enough on install or perhaps the enough vibrations had done enough to shake them loose. This time I decided to add some blue locktite just to be extra safe. The cam and crank sensors weren’t too difficult to replace, it almost made me paranoid thinking “somethings not right, its never this easy.” 🤣 I took the valve cover and coil packs out as a single assembly. In order to separate the two, I had to drill through the underside of the valve cover right underneath the rivet nuts so that I could chisel them out. Once I got the coil packs ready and the new valve cover installed, it was time to check the gap on the spark plugs. I increased the gap from .44” as per the Haynes manual to .48” as per the instruction I was given by the 2JR guys by email. The big thing I noticed here was that the spark plugs in cylinders 1 and 4 looked similar in that they were dry and blackened up to the tip of the electrode where it was whitened from the heat. Cylinders 2 and especially 3 were completely blackened and wet looking with 3 looking more sludgy. This should have immediately been a big red flag but it still hadn’t clicked with me yet.

Once everything was installed it was time for the moment of truth to go start the car and see what it does. Unfortunately the car didn’t want to start at all, and I was like “damn, the more I try to fix this thing the shittier it gets🤣.” It cranked strong, so I tried blipping the throttle while starting it but that caused it to backfire. So I knew my voltage, air, and fuel all had to be good here so the only thing that could have been wrong was timing still. I swapped the coil pack connectors on cylinders 2 and 3 and told myself “well this is either going to be a lot better or a lot shittier,” and voila it started and idled like a charm. I must have incorrectly swapped them before when cutting back the insulation to inspect the wires. It’s late now so I don’t really want to drive it around and bother the neighbors and everybody so I’m going to get back at it tomorrow, run the idle air relearn, and see if the car has any more hiccups it wants to throw at me. I may even go back and reinstall the 255lph fuel pump since I know that it shouldn’t be a problem anymore and I have the extra o-rings ready to go now.

Things are going better now. I started the car and let it sit and run this morning, then swapped back to the 255lph fuel pump. The car was running really rough at first, I believe this was due to the messy spark plugs in cylinders 2 and 3. The engine was misfiring at idle and on acceleration, and backfiring into the exhaust frequently. I think it was mostly unburnt fuel from poor spark at those cylinders. I drove the car up a hill to put some load on the engine and it sputtered a little and then started running a lot smoother. I filled up the tank with new fuel, and drove it around some more. I’m now getting 2 engine codes; one code for a misfire on cylinder 4 and one code for a high idle. I’m a little happy that it’s a cylinder 4 misfire instead of a random misfire because that narrows things down. When I got back home the first thing I did was pop the hood and check the hose I put together to go from the PCV valve to the intake manifold. It was whistling until I pinched it, so I believe there’s a vacuum leak there which might explain both engine codes.
Before I was checking for vacuum leaks earlier this month, I had the PCV and vent hosed together going to my oil catch can. Is it better to route the PCV to the catch can or straight to the intake manifold like stock? I know on my old engine cylinder 4 exhaust port was caked in oil and carbon deposits far beyond the other cylinders, and I assumed it was because of the PCV plumbing.

I’ve made some more good progress.

So I just ran a new hose from the PCV to the intake manifold and left my oil catch can between the valve cover vent and intake pipe. I have a second oil catch can I can use between the PCV and intake manifold, but I’m going to leave that alone until I can fix all my other issues first.

I swapped the spark plugs between cylinders 2 and 4; cylinder 4 spark plugs was black and wet which tells me that fuel isn’t being completely burnt so it’s probably not making spark. I then got engine codes for high idle rpm, cylinder 4 misfire, and random misfire. There was definitely an issue at cylinder 4, and the random misfire was probably due to the dirty spark plug now in cylinder 2. I bought new spark plugs last night while racking my brain over the possible causes and gapped and installed them this morning. The high idle and misfire 4 codes still remained so I narrowed the issue down to cylinder 4 coil pack or connector. I checked all 4 connectors’ pin 1 voltage and pin 2 grounds and everything looked good. The issue was either the pin 3 signal from the ecu or the coil pack itself. To test this I pulled the cylinder 1 and 2 connectors off, removed the cylinder 3 and 4 coil packs and inserted spark plugs into them. I used jumper cables to ground the spark plugs to the negative battery terminal, and had my brother turn the engine while I watched the spark plugs.

Test 1:
Connector 3, CP 3, SP 3 = Good Spark
Connector 4, CP 4, SP 4 = No Spark
Test 2:
Connector 3, CP 4, SP 4 = No Spark
Connector 4, CP 3, SP 3 = Good Spark
Test 3:
Connector 3, CP 4, SP 3 = No Spark
Connector 4, CP 3, SP 4 = Good Spark

The common denominator here was the coil pack from cylinder 4, so this had to be the problem child. I was suprised because this was one of my BRAND NEW NGK coil packs. I replaced the bad coil pack with one of my old ones, took it for a test drive, and the misfire code is completely gone now.

I’m still left with the high idle RPM code, so I took my smoke machine out to check for vacuum leaks. Surely enough, I have a new leak at the front passenger corner of my valve cover. I must not have installed it correctly, so I’m going to head over to autozone and just get agasket to see if that’ll fix it.

It’s as close as it’s ever been to running right and I’m so excited. I still have a few smaller things to tweak; my side exhaust needs to be raised and my parking brake needs adjusted to prevent the car from rolling on an incline.

Alright so I’m getting cylinder 4 misfire codes again. It was only happening at first when I the car was idling with AC off. Anytime there was any load on the engine it seemed to run smooth. The engine code would only come back sparingly if I let the car sit and idle for about 20 minutes or so. I bought another NGK coil pack to replace the old Hanshin coil pack I was using as a substitute but it didn’t seem to fix the issue. The problem seems to be progressively getting worse because the engine code is coming back more frequently when sitting and now it’s coming back while driving. I think there’s an electrical issue killing my coil packs somehow. Before my engine swap, I added a grounding jumper going from the battery to the head where the coil packs are grounded and from the head there to the alternator bracket ground. I removed the jumper to the alternator bracket, but that hasn’t seemed to change anything. I’ll try disconnecting the jumper from the battery to the head, if that doesn’t work then I may consider wiring new grounds from the coil pack connectors straight to the battery. I really wish I could get my hands on a spare 04-06 Spec V engine harness to replace the coil pack wiring with a larger wire size without sacrificing my original harness, but all the junkyards have is 1.8’s.