sr high rpm misfire, enthalpy tune? help please

[samplesurf]

alright heres the deal this all started a couple weeks ago when i took my car out one night and noticed it slightly missing occasionally when i was just cruising, then after i got on it it misfires at about 4k rpm and on but its ignition as my wideband shows afr is ok but its like its hitting a limiter.

so far ive:

-checked all grounds and even relocated some such as the coil pack ground
-all injectors are firing
-swapped to a different z32 maf
-swapped ignitor chips
-got new coil packs
-changed spark plugs
-fuel pressure is ok and injectors not leaking as i can tell from my gauge that still holds pressure with the car off
-checked all sensors with nissan data scan via the consult and they all check out
-cant be the knock sensor since it doesnt work above 4k anyways


so im starting to suspect my enthalpy tune or ecu, it seems the more i search i can find more people with enthalpy tunes having the same problem, i do have another stock ecu but it isnt going to work with my maf or injectors, so any other help is appreciated


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[fliprayzin240sx]

What sparkplugs are you running and what is it gapped at?

[samplesurf]

both are gapped at .028 and one set is hks and the other ngk, they were both run prior without any problems, spark plugs are not the problem

[godsmack]

ya but what heat range are the plugs? you might need to run a cooler plug.

[REVGASM]

i swear mine has the same issue

[twisties]

i too have seen enthalpys do that

[samplesurf]

so u guys have enthalpy tunes and have had the same problem?

[samplesurf]

ya but what heat range are the plugs? you might need to run a cooler plug.


one set is one range colder and the second is 2 ranges colder, its not the plugs because it just started with this problem, it has run for years with the same type of plugs

[Sleepy240]

Are you using a FPR? When I had my enthalpy tune I had to run a FPR that I was not originally running.
Also what does your timing look like?

[samplesurf]

Are you using a FPR? When I had my enthalpy tune I had to run a FPR that I was not originally running.
Also what does your timing look like?


ive got an automotive fpr and its working correctly, also timing is at 15 btdc and also seen as correct with the datascan

[V8slayr]

The only issue I have is my car will not idle correctly, idles at 23-25 AFR. Not 100% it's the ECU though, not sure what could cause that. As far as my tune itself is concerned my car runs great, no problems whatsoever. AFR is good all the way to 8k, power is as smooth as silk. I run 18 psi on a T3/T4 w/ my Enthalpy tune

[4x4le]

ive got an automotive fpr and its working correctly, also timing is at 15 btdc and also seen as correct with the datascan
nissan datascan cannot tell you what your timing is. All it does is assume your base timing is set correctly and that is why you see it say 15* btdc. You still need to get a timing light to ensure your base timing is setup correctly.

[samplesurf]

nissan datascan cannot tell you what your timing is. All it does is assume your base timing is set correctly and that is why you see it say 15* btdc. You still need to get a timing light to ensure your base timing is setup correctly.


i know base timing is correct, i installed the cams over a year ago and stabbed the cas correctly then, i did no work before it started acting up and the timing was checked with a timing light back then, and datascan does tell me what the timing is, it moves as we drive it throughout the rpm band as it is supposed to to, and if the timing was off then it would not allow me to reach redline when driving without backfiring as long as im not wot

[4x4le]

i know base timing is correct, i installed the cams over a year ago and stabbed the cas correctly then, i did no work before it started acting up and the timing was checked with a timing light back then, and datascan does tell me what the timing is, it moves as we drive it throughout the rpm band as it is supposed to to, and if the timing was off then it would not allow me to reach redline when driving without backfiring as long as im not wot

If it was checked with a timing light and you have not adjusted it since then it is most likely correct still. But I dont car if the cam timing is correct and you stabbed the cas correctly, you always have to get out the old trusty light.

And datascan cannot tell you your actual base timeing or your actual timing unless your timing is set correctly is what im saying. If you turned your cas it would still read correctly in nissan data scan. It always assumes your timing is set correctly. If it reads 15 and you set it to 15 with a light then your numbers will always be correct, but if you set it wrong, say your off by 2*, it will be off by the same 2* through out the entire range.


What you do need to do though is check your codes through datascan. Also look and see if your sensors are reading anything stupid on a cold engine, like if its 80* outside and you havent driven the car all day your coolant temp should read 80*. Also see if your pulling wierd maf voltage ect.
Now do dataloging too. Create the problem, once the problem happens pull over, save the log and review it. See if any sensors are acting funny during the break up. If you get any values jumping around like mad when its breaking up diagnose the sensor and the related wiring.

I dont care who tuned your ecu, if your ecu hasnt been touched since it ran correctly, that tune is still the same as it was when you got it and you have a mechanical problem.

[steve shadows]

Did you check fuel pressure UNDER LOAD?

You need to run a gauge inside the car and make some pulls and watch it.

if the needle is fluttering or slowly bleeding off you have a bad fuel pump

Sometimes bad voltage to the fuel pump will cause this high rpm fall off in pressure too.

[samplesurf]

Did you check fuel pressure UNDER LOAD?

You need to run a gauge inside the car and make some pulls and watch it.

if the needle is fluttering or slowly bleeding off you have a bad fuel pump

Sometimes bad voltage to the fuel pump will cause this high rpm fall off in pressure too.


that totally makes sense, except that my wideband shows me staying the same or going richer under the misfire, so its not lack of fuel

[4x4le]

that totally makes sense, except that my wideband shows me staying the same or going richer under the misfire, so its not lack of fuel

Thats what I was thinking, except the possibility you have a slower refresh rate on your wideband. Some dont refresh as fast as other to give you smooth needle responce or to keep the gauge readable if its digital. A pump with faulty wiring and a slow wideband gauge could read good still.

I wouldnt write the pump off completly.

[johngriff]

Coil pack wiring at the connectors. Had it happen on multiple SR's.

Wiring just bakes after a couple of years.

[SidewaysNJ]

No one has mentioned this but i'm going to throw it out there. maybe you have a boost leak. I remeber i had a coupler that was cracked but the crack only opened up under higher boost. the air that was escaping was causing a rich condition.
Also make sure all of your intercooler piping clamps are tight. t-bolt clamps are the way to go.

[KiLLeR2001]

i had a similar issue a while back, ended up being a coilpack. it would start misfiring around 5000 rpm, and i went around replacing everything but the damn coilpacks. Lesson learned i suppose. +1 for coilpacks/wiring

[steve shadows]

If it's ignition "misfire" then it will feel like you are hitting a wall, wont be very violent just like the motor stopped for a second.

If it's fuel it will be less apparent or obvious but will get worse as you build RPMS.

Believe it or not the FP issue is usually caused by Voltage drop or a slowly clogging walbro filter.

This is why the dyno is nice to use for diagnostics too, you can just stand there at 7K rpms under full boost in steady state watching the FP gauge.

This is really common issue on high output SR cars that need fuel.

Plugs make sure you are using at least cold range 7 if you are using NGK and also check your base CAS Timing, this can cause a simlilar problem as well.

If you are local to CA I offer a Diag-Tune package for 300 bucks.

Baiscally we do a before and after pull and in between I set your CAS in the head again, re do your plugs, test for vacuum leaks, adjust cams, and other mechanical thinsg, that when they are all added up the car gains typically 20-40 whp and runs 10 Times better.

Just something to remember if you are having similar issues and are close to when I operate. THis would do wonders for your setup if the car is just "not right"