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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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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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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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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.
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.
 

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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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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.
 

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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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