Just got my car back from a whole bunch of transmission work (new tranny with custom stall tc and hd shift kit).

**** works awesome...till I hit high rpms

Only under load am I experiencing issues. The code I pulled was P0507, performed the relearn and reset code. It came back later.

Now there is another symptom, may or may not be directly related. Only happens during WOT above 4500RPM and under load (not in neutral). I get up into that range and it misses/pops, sometimes it will catch as if I'm not getting spark then getting spark all the sudden.

Obvious things
Replacing plugs and PCV valve checking seals and replacing gaskets while there
Checking for intake leaks with brake cleaner
Inspecting intake/throttle body...
Ohming injectors while doing plugs
Checking coil packs

Oil good, tranny new, fuel good....

Anything I'm missing?

 

Also I should mention that the idle seems to be normal.

 

Does seem odd to get that code then, as it is normally related to the idle being to high / or crapped out completely

http://www.nissanclub.com/forums/200...-expected.html

 

yeah i know right.....

 

so no thoughts?

I havent had the chance to do anything yet.

again the shuddering/missing whatever you want to call it is at high rpms underload...

no idea if the cel is directly related or not...

 

Well none other than the ones you are going to be checking, you seem to be having a similar issue with your high RPM wot push as I am having except I am getting no codes. this is my thread on my issues which you have given some comments in http://forums.maxima.org/5th-generat...0-5000rpm.html

So it appears we are both going to be checking similar items as we are both displaying the same kind of misfire/bogging in the higher rpm's. with the exception you have the p0507 code. I will be checking more into the same items that could be suspect

- prcats
- plugs
- coils
- IM leak
- 02 sensors
- T-stat
- injectors
- MAF sensor
- compression check

Here's a video I found might be of some interest for testing the cam and crank position sensors as well as how to perform an idle relearn ... I just about gasped when I watch how brutal he was when cleaning the TB ... don't think I would be doing that to my TB butterfly to soon

http://autos.technologybizbuzz.com/n...ting-by-wells/

 

no cats =)
my plugs will be changed along with valve covers, and pcv
02 sensors maybe...hmm should give a code though?
tstat is good i checked with the ir thermometer as said in other thread
injectors will be ohmd out when swapping plugs
same with compression check

 

507 is a high idle code, not sure how that would affect high rpm performance other than one of the causes for a 507 is a vacuum leak.

 

yeah i know...funny part is...my idle is normal??

 

Two things:

O2 sensors can get "lazy," and not throw a code. I had an issue with one of my O2 sensors doing just that.

No CEL, but when I'd let the car idle for more than 5 or 6 minutes, it would start running incredibly rich and dumping fuel into the car almost to the point where it would stall. Once I revved it up or drove it around, it would idle fine again. Put a scanner on the car and checked the sensor voltages. The front bank 1 sensor was barely reading. Swapped it for another O2 sensor, no more problems.

Second, what are the possibilities of a vacuum leak of some kind not becoming apparent until the car is under extremely heavy load? (E.G., the amount of pressure on the system sort of "forces" the leak to open up, but once the car settles down, it closes?)

 

Also, what about a faulty knock sensor?

 

hmm maybe?

 

As I stated in Ghost's thread, which seems to be very similar to this one,
vacuum leaks are normally only evident under idle and low throttle, when vacuum is highest.
Anything over half throttle (maybe less) and you're running little to no vacuum at all.

This is why intake leaks almost always affect starting, and idling.
There is a simple way to check for intake leaks, although I don't think there's a point in this situation, but I'll tell you anyways.

-Take off the filter, put a hardcopy book up against the intake pipe while the engine is running (don't put a rag, etc there, the engine will take it away from you ) if the engine bogs out hard or dies, you know the system is well sealed.
If the engine keeps running, you know you have a leak, and you'll probably hear it at this point.

That's an old test, it's not as valid as it once was because of sensors, etc, but it still works to some extent. Other than that, you should be hooking gauges up.

 

My first guesses would be knock sensor or spark plugs. Probably not a vacuum leak since those mostly only affect idle and low throttle operation. I guess it could also be a blockage (serious misuse of a gasket or RTV) that only becomes apparent up top when it's starving the engine for air. Not sure if that shop would have taken off your IM for a transmission job though.

 

Yeah they did not have to take it off, I'll check into the KS as well. The plugs are getting changed this week. The IM hasn't been off since I got a new engine so it's not that, last time I put too much on it actually bogged during start up but then ran fine. Thanks for the input.

 

just noted that my gas mileage is 15mpg .... so yeah im thinkin coil or plugs

 

video clip of what its doing

 

Does your AT light stay on when you start it?

 

nope

 

Not even for 5 seconds right when you start it?

 

Sounds like a single cylender issue (Video). I would think the sound of the hesistation would be diff if it was something such as knock o2 or mass air flow and such. I would bet its compression plug coil or injector

 

no, less than a second it stays on...mind yall i havent replaced the plugs yet

 

honestly in looking at it seems like i would do plugs and start testing the coils.as well for good measure try swapping out the tranny sensors if you have them off the old tranny. but seems ignition related.

 

yeah considering the gas consumption ive been assuming a fouled plug...no spark mean gas is just pouring through

 

happy with the stall as far as you can tell so far?

 

yeah its awesome, once i fix this ill write a review =)

 

Isn't there a specific code the ecu would throw for this? How do you check this?

 

KS or cam sensor maybe, or cylinder misfire. Yes it should pick it up but not always

 

well changed the plugs wasnt it, havent had time to do anything else yet

 

coil packs looked good no oil on them, injectors all around 13.5, sprayed the uim with brake cleaner and found no leaks

i did notice that my idle is high when i first start the car but once i put it in drive it goes down, and stays that way...

i have a spare throttle body i might try swapping out and doing the relearn, but i still dont know about the high end missing

 

oh i should also mention that i can smell a faint bit of gas at times after driving or revving..unburnt fuel no doubt

 

Ok so all coil packs replaced
all plugs replaced

still does that **** at high rpm....not just WOT, but heavy throttle...

CEL light is gone now, but code is still there along with an 02 sensor code pending (headers with 02 sims, worked fine before tranny install.)

only thing that changed is the crank sensor near the tranny, it was taken out then put back in....but how would that effect gas mileage and only high rpm...?

i should also note that my gas mileage is 28-30mpg if driving normal highway.....but as soon as i start getting on it and it "misses" like that then it drops to 16-20ish

 

Could be the sensor was not properly tightened down or the wiring harness isn't fully clipped on.

 

yeah but you think it would act differently if faulty/not installed right.....if the gap was incorrect then it wouldnt start...plus then the gas mileage and ONLY at high rpms ?

im thinking im going to have to bring it in and have someone hook up their diagnostic tools and see what the tools say while at high rpm and under load....since my ecu wants to be flippin lazy

 

Still seems electrical. Could be a injector/injector solonoid. Don't know the test procedure for them have you checked them?

Is the engine telling you what cylinder is missing or is it 'multiple'

 

I ohmed my injectors again and all are saying the same thing..usually they spit less fuel than more =/

and with the gas mileage drop it seems like its spitting extra fuel or not igniting like it should...

maybe something to do with timing...but again its intermittent (90% of the time it happens) and only at high rpm

 

Cars will run with huge spark plug gaps (like mine did) before eventually the gap is too great to overcome. Could be just a touch loose and higher rpms would be where the looseness affects it the most. Worth at least checking out.

 

yeah i guess ill get on my *** and check it out...worse that can happen is the car wont start and ill just have to readjust it....

 

wow...so strange...it was the mpu or cps whatever you want to call it...it looked a little close to the teeth so i adjusted it just a hair and its not studdering at more or missing anymore, but it does bounce off the rev-limiter then shift..

 

unplugged my battery..gonna leave it like that for an hour or so then reset the codes and take it for a drive....