Possible Maf problem, need help diagnosing

[bellis_GTR]

Mine is def not bolted down. I dont think yours is either, if its a stock setup its not. I wouldnt know how to bolt it down without drilling into it or something but ill keep that it mind. Will check the ecu soon. Maybe do a ECU reset (cutoff battery for more then 30 secs and then retry). More ideas are always welcome

yeah mine are. I have HKS intakes.

[aN4rk1]

So I did some poking around with my other mechanic and we retarded the timing and it seemed to pull a little better. What we think is happening now is that when we did the waterpump and timing belt change, the timing on the crank might have been a little messed. The two cams seem to be absolutely perfect, as we did a quick check yesturday, but we didnt check the crank as we didnt have enough time. We are going to rip it all apart next weekend and see what she says.

Or the plugs, bad tips getting snuffed by boost. Should get a misfire code for bad spark, right?

Edit: Stock boost plateaus near 5500RPM...

I have a hard time even getting to 5500RPM, be she used to pul and pull HARD! I will check them, next weekend. I am kinda am and am not hoping its the coils. I am hoping so I can get the yellowjackets, but not hoping as I can get the car on the road faster lol

doesnt sound like a maf issue to me.. sounds more like plugs/coils to me. did you test your coils? check for fouled plugs? gap plugs properly?

I have not, how would I check the coils? and how to gap them? The boost restrictor is gone.

[aN4rk1]

edited. Didnt mean to double post.

[TW]

You can test the coils by testing the resistance in the coils. Use a multimeter and touch the leads on the outmost pins on the coilpack connector, if I recall correctly. You need to disconnect the coil pack harness from each coil to get at the pins. You are looking for 0.6-0.9ohms. Don't forget to touch the leads to one another to get the resistance in the multimeter and subtract that from the value you get from the coils.test each coil.

To gap your plugs, you need a feeler gauge. You can get on at caca tire. You want to make sure the gap between the tip of the plug and the metal piece is 0.8mm. Pull each plug and check for carbon fouling.

Have you checked for boost leaks as well?

[aN4rk1]

Well i finally got around to doing an ECu test. Threw code 55 which is the code for all is good.

Or the plugs, bad tips getting snuffed by boost. Should get a misfire code for bad spark, right?

Edit: Stock boost plateaus near 5500RPM...

The plugs are semi new. I put them in when i got the car which was about 3ish months ago. NGK BKR7E's

You can test the coils by testing the resistance in the coils. Use a multimeter and touch the leads on the outmost pins on the coilpack connector, if I recall correctly. You need to disconnect the coil pack harness from each coil to get at the pins. You are looking for 0.6-0.9ohms. Don't forget to touch the leads to one another to get the resistance in the multimeter and subtract that from the value you get from the coils.test each coil.

To gap your plugs, you need a feeler gauge. You can get on at caca tire. You want to make sure the gap between the tip of the plug and the metal piece is 0.8mm. Pull each plug and check for carbon fouling.

Have you checked for boost leaks as well?

I will do this thanks. I have semi checked for boost leaks by going over each pipe so on as best as I could. I dont have an actual leak tester.
This is all pointing to the fact something might have been wrong with the car when I did the waterpump and timing belt change. I am planning to rip the front off again and check the timing. I retarded a timing a bit and test drove, and then a bit more and drove again. The car seemed to pull better each time I retarded the timing. Hopefully i can get this fixed.

[BenC]

Is your idle wandering at all?
Does it misfire when your losing power or still reving smooth?
I would pull out your plugs and see what color they are Also see what your boost gauge is reading at idle and at full boost and report back

[MarusGTR]

Just to add, did you consider that maybe it was your wastegate that was stuck open? The turbos start surging at 3000ish RPM, so if your valve is weak or there's problems with the actuation you could be just getting atmospheric pressure past the initial surge.

Go to the EN-350 page in the RB26 manual. You can troubleshoot your wastegate from there.

[aN4rk1]

Is your idle wandering at all?
Does it misfire when your losing power or still reving smooth?
I would pull out your plugs and see what color they are Also see what your boost gauge is reading at idle and at full boost and report back

Idle doesnt wander THAT much. 95% of the time itll idle perfect at 1k, but sometimes when I come to a stop and step on the clutch before parking, or right after a cold start, idle will jump to about 1.8k and then sit there for about 5 seconds and then come back down to 1k. It revs smooth, no misfire when losing power. Car misfires in general though, but I think that might be due to the ecu tuning at 100 octane/running rich. Idle boost is about -2 on the stock boost gauge (-7 to 7 x100hh/mg) and max boost currently id say about 3.5-4?

Just to add, did you consider that maybe it was your wastegate that was stuck open? The turbos start surging at 3000ish RPM, so if your valve is weak or there's problems with the actuation you could be just getting atmospheric pressure past the initial surge.

Go to the EN-350 page in the RB26 manual. You can troubleshoot your wastegate from there.

I havent though about this. I will do this and report back thanks!

I checked the timing again today. It seemed as though the crank was off about 2 teeth. We fixed it all up and put her back together and tried again. She seems to do the same thing but now its about 7k, instead of the 5.5ish-k as before. So its a little better. Iam going to take it to a Nissan specialist I know and get the timing PERFECT, then we can rule that out I think. It did the 7k on city streets, but wheN I got back on the highway, it seemed as though it was at 5.5k again, that seems like an airflow issue, which again...points to mafs. What I think I want to do is ask around and see if I can borrow someones PROPERLY working mafs and see if that fixes it, if not then I check the coils/plugs, then wastegate, then...

[MarusGTR]

Good luck man!

Btw did you say 7k RPM on the street? You're really running her huh? Stock oil pump?

[aN4rk1]

Good luck man!

Btw did you say 7k RPM on the street? You're really running her huh? Stock oil pump?

lol, I knew someone would ask that. I dont pass 3.5k daily driving. This was just a test to see if the problem was fixed!
And thanks, ill keep posting.

[BenC]

If it's not miss firing while losing power you can pretty much rule out plugs, coils, ect. 3.5-4 on the stock gauge is too low. Should be around 7 I believe

[MarusGTR]

If it's not miss firing while losing power you can pretty much rule out plugs, coils, ect. 3.5-4 on the stock gauge is too low. Should be around 7 I believe

7mmHg is 14.7psi or 1 atmosphere...isn't stock R32 boost 8psi? Can't find the source I found back when I was checking for it. My GTR is stock but I dont look at the boost gauge when I accelarate.

I need a copilot

[aN4rk1]

7mmHg is 14.7psi or 1 atmosphere...isn't stock R32 boost 8psi? Can't find the source I found back when I was checking for it. My GTR is stock but I dont look at the boost gauge when I accelarate.

I need a copilot

This correct. 7mm/mg only after boost restrictor is gone....and mine is

Another question. My Ecu still has factory Japanese tune. I plan to get it tuned at some point next year ($$ issues) but in the mean time, what should I gap my plugs to? and what king of plugs? I am using BKR7E's right now which I was told were the best plugs. If it is my coils, I will be getting some YellowJackets and I want the best Coil + plug + gap combo for my car with Factory ECU tune.

[BenC]

Yeah everyone seems to claim 14 psi with the restricter removed. I thought even with the restricter it was a bit higher than 8 but your probably right. I haven't even driven a gtr with one. Anyways if you pull your plugs and inspect them it should give you a good indication of whats going on in the cylinders. Your problem probably lies in your fuel or air being off at WOT. I'm assuming you checked your ignition timing via timing light afterward?

[aN4rk1]

Your problem probably lies in your fuel or air being off at WOT. I'm assuming you checked your ignition timing via timing light afterward?

Yes the biggest problem is at WOT.
I have not done this yet, Iam trying to schedule an appointment with a specialist.