I feel like I just lost 60hp..

[JDMricist]

Hey guys, Having a bit of a problem here and hopefully someone could help me troubleshoot this issue.

Problem: Once the engine warms up (after about 5 min after start up) It feels like I lost like 60hp.
Symptoms: You know that slight vibiration feeling the engine gives when you floor the gas pedel at 4th gear @ 1.5k-2k rpm and the car feels boggy? (for lack of a better word) Almost like I unplugged one of my spark plugs but the engine idles smooth.
Performance: Car idles smooth at 900rpm, temp needle is pretty much between Hot and Cold, Oil pressure is between the second mark and 60 (closer to 60), just did a seafoam and fuel injector cleaner from Lucas, oil change, swapped spark pluggs to NGK iridums about 4 months ago, 140k miles.

This problem has been going on for about a month but getting worse every week.

Hope I gave enough info. Ask anything you guys need. I would love to solve this problem before taking it to my mechanic.
Thanks!

[BigTDogg (MA)]

Eh hem... technical forum???

Check your timing when the engine is warm, do a power balance test (pull coil packs one at a time, replacing them before moving to the next, listening for change in idle) and check for ECU codes (not all trip the CEL).

[A Paratroopers 300zx]

There could be many issues that are causing this. I would start by checking all electrical connectors and vacuum lines. Specifically on the CAS, TPS, Coil packs and PTU. Oh and the VG30DE(TT) engines are very particular about spark plugs... NA stock = NGK platinum PFR6B-11 gaped to 0.044" (1.1mm) TT stock = NGK platinum PFR5B-11B gaped to 0.044" (1.1mm) Hope that helps a bit!

[nissanfreak12]

I would definiely check your timing as BigTdogg said, I had a similiar issue, ended up being timing was off 10 degrees. Just make sure you check it at the #1 cylinder, the PTU loop will no give you accurate readings

Definitely put the right plugs in there as paratrooper said, It make a world of difference

[JDMricist]

Thanks for the replies guys!
Alright, so I spend like an hour making sure ALL my vac and fuel lines are secure. Even reattached some but still same thing. Once the car warms up and the oil pressure drops a bit then it gets all slow again. I'm using NGK Iridum plugs that don't need to be gapped (even says on the front of the car)
Timing is also on spec.
However, I just noticed that the gas pedal gets noticeably easier to depress (even kinda sticky) when it's going through this slow mode. Any more tips and stuff to check would be greatly appreciated.

[BigTDogg (MA)]

I'm using NGK Iridum plugs that don't need to be gapped (even says on the front of the car)

False, they need to be checked at the very least. Be cautious though as the electrodes are delicate. Using feeler gauges, if the gap is supposed to be a 0.045", then use a 0.043" to check.

0.045" is going by memory for an NA, I'm not sure what it's supposed to be.

Did you do a power balance test? Search for how to do that, if you have a problem cylinder that may help you find it. Any ECU codes?

[nissanfreak12]

/\/\.044

[nissanfreak12]

Just random thought, are you sure both throttle bodies are opening up?

Do we have a manual or auto, if auto run the diagnostics on that comp, way to do it is around here somewhere

[JDMricist]

So I finally got enough time to check the codes and it's givng my code 34 - knock sensor. From what I heard is this is the sensor that senses knocking and limits your power which would explain my power loss. How hard is this thing to replace?

[BigTDogg (MA)]

Very, it's below the lower plenum

Search for the bypass

[CrazedZ32Owner]

or if you need to dive down in there to replace somethings now would be a good time.... i'd like to keep the knock sensor

[BigTDogg (MA)]

or if you need to dive down in there to replace somethings now would be a good time.... i'd like to keep the knock sensor

Fair enough, but a bypass or relocation until your next timing belt job or engine pull would do the trick.

[Sdavne]

Injector could be failed, this happend to me it started once in a while and than happend all of the time.

[JDMricist]

Alright, so the knock sensor bypass did the trick! Reset the ECU and now it's running amazing right now. Thanks alot guys for the help! Glad I got her fixed back up for the Nismo Fiesta autocross event this weekend :P

[CrazedZ32Owner]

glad it helped man

[mkhoid]

might want to look into buying a knock sensor relocation from Bernie...instead of using resistor.

[JDMricist]

might want to look into buying a knock sensor relocation from Bernie...instead of using resistor.

I may have to do that.. I'm still pulling code 34 even with the resistor.. It's fine for a good 2 days after resetting the ECU but code 34 is always there and I'm still having the same problem.. Bought an ebay knock sensor a couple of hours ago so I could just relocate it.

[aviatorwes]

Noticed you said you used seafoam. Where all did you put it (fuel, oil, vac, all 3)? If your car has alot of miles on it your cats could have gotten partially clogged from all the burnt off impurities/carbon build up. Just another suggestion. Knock sensor will do it too like stated above.

[JDMricist]

Alright, so it seems after resetting the ECU, the car runs fine for 2 days till the problem occurs again.. Even after installing that 1/2 watt 1 megaohm resistor and resetting the ECU, I still get code 34 but the performance is fine till the next day. Hopefully installing the new knock sensor will fix my problem but I have never heard of the megaohm resistor trick not working which is why I'm worried..

[JDMricist]

Ok, so this time I replaced the resistor and unplugged the battery overnight and am getting code 55 for the first time so I think I'm good now! I'll post an update next week.