travisinthe8

Im gonna start off by saying im aware there are a number of threads about this issue but i cannot post anywhere else as its a new account.

Spark plugs ~4k miles

Coils ~ 10k miles

wires brand new

aem cold air intake

ebay header, megan racing header back

sohn adapter

20w50 VR1 full synthetic

-Car often times wont revv past 6k in 2nd gear

-same issue at about 7200 rpm in 3rd

-car begins to flash CEL (misfire) during high revv conditions

This started on my way to the track, i noticed the car was “breaking up” at about 6k in second gear and was hesitating to revv up to 7.

Replaced plug wires on track because I found one that was loose, and no fix.

While down the back straight i ran into the misfire issues at about 115mph, said **** it stayed in the throttle and continued to race.

A few turns later with about 1\8 of a tank of gas i swung around a left turn really fast and the car shut off and i had to be towed off of track.

needless to say i filled it up with premix and gas and hopped back on the track with my misfiring rx8. Wasnt worried as i have replacement engines and dont mind putting the wrench time in. Car kept misfiring for my next 6 track sessions. And now today when i was street tuning, it refused to get over 6k rpm. I know it isnt a tune issue because i reverted to factory and had the same problem.

Sorry you had to read my tangent i went on

just gonna go ahead and say i think its the fuel pump because live data on versatuner shows the injector pulse cutting at 6k

gonna do a smoke test for vaccuum leaks

dont quite have the ability to test live fuel pressure with a gauge. Or do a compression test, im broke asf and put off buying tools

Car always starts, hot or cold dosent matter im aware that dosent mean i have good compression just that my ignition system is functioning properly

THANKS!!!!!!!

Loki

iTrader: (1)

Does your megan headerback include a catalytic converter? Because it sounds like a clogged cat, which will kill your engine in short order. Cheap cats are not expected to survive being attached to a rotary. If you don't have a cat, you could be ingesting oil into the intake, check for that.

It's not your fuel pump, there is no way for injectors to know what the fuel pump is doing and change their pulse width. Fuel pumps usually stop entirely, they don't pump less. The P1 injector will cut out at some point before redline when P2 takes over and secondaries are already on. It's load dependent, not speed.

Loki

iTrader: (1)

The forum appears to have eaten my post. It's not your fuel pump and P1 injectors cutting out before redline is normal, secondaries and P2 take over at some point based on load, not speed. Either way injectors have no way of knowing what the fuel pump is doing, their pulse width is independent of the supply of fuel.

It sounds like your catalytic converter is clogged, if you have one. If you don't, look for oil in your intake. If you have a cheap cat, don't expect it to survive long and be careful because it will take your engine with it.

travisinthe8

I have a catless midpipe, and the intake piping is clean, I see what you mean about the injectors switching i did only have one of the graphs up when there are 2, could overfilling the engine with oil cause this? I checked my dipstick and it was high but i figured that wouldnt cause much of an issue considering the engine probably still burns a bit of oil even with the sohn adapter.

im gonna crack the tank open and check the sock. Its definately feels like a fueling issue, i can check for oil behind the throttle body.

This issue ruins the cars driving experience completely, cant touch redline or my car gets extremely angry. Have to stay below 6k rpm

travisinthe8

Also when i revv the car in neutral, the whole car studders and shakes around 4-5k rpm, and kind of makes a sputtering noise out the exhaust

Loki

iTrader: (1)

I don't see those as signs of fuel pump problems. Does this happen regardless of how much fuel is in the tank? You can run a can of Seafoam through the tank if you're worried about contamination. No guarantees but run a full can to a full tank and see if there's a change.

Does this also happen at partial throttle but same rpm, or at higher rpm, or not at all?

My guess is more ignition problems. What coils do you have?
Any OBD codes besides p0420 for the missing cat?

travisinthe8

Oem coils, they are like new and i used my coil tester on all of them, misfire rear rotor. Swapped the coils around to the front still have rear rotor misfire

i can scan codes when im home

i can check my spark plugs for “fouling”, last time i did the spark plugs the rear leading was missing its grounding electrode

this happens at WOT under high revving conditions 1st 2nd and 3rd gear havent tested it in 4th cuz i dont highway drive and cant get enough road to test without being arrested

travisinthe8

Also maybe this is a dumb question but do i premix with the seafoam?

ps i premix 8oz for 8gal every time i fill

travisinthe8

Only DTC i have at the moment

P0037 - HO2S Heater Control Circut Low

Loki

iTrader: (1)

K, I assume your rear O2 is disconnected?
Premix with seafoam - I don't see that it matters, you could skip the seafoam tank just in case. What premix oil do you use?

Has it always had the AEM intake and has it always had this problem? What are your fuel trims (short and long term ) on a warm idle?

travisinthe8

Thank you for your help by the way,

went ahead and replaced all 4 spark plug wires previously had NGK and had to replace them with import direct wires from oriellys…

Replacing the spark plug wires fixed the misfire on the top end, that was an ignition issue like you said. But the car is still struggling to revv over 6k.

The car revvs freely up to 6k but hesitates to climb for a second, almost like its choking itself out. As i continue to push through the throttle it makes it up to redline.

I exclusively premix with Idemisu Rotary Racing premix, and have the omp duty cycle cranked up 20%

I only took datalogs of when i was doing pulls to try and see why it was hesitating at 6k but i will go out to my car and check the idle fuel trims.

This problem occurred after i installed the AEM intake, i know i installed it correctly i intentively followed the included instructions and capped all of the vaccum lines off. Unfortunately im stupid and threw the stock intake away after i installed the AEM, so i cant revert to stock to see if that solved the issue.

i used MAF cleaner before installation, and then a few weeks later it was having a tough time idling so i clean the MAF again which fixed that issue.

Is it possible the ESS could become contaminated and provide the ECU false speed readings which in turn causes the motor to revv improperly?


This engine has ingested water a few times but that has never seemed to stop the renny, dry it off start it up and run it again.

wish i could run a compression test, i might have a buddy who could do one for me.

travisinthe8

Also yes the rear 02 is disconnected because it would not fit into the bung by the transmission im assuming because it was a cheap exhaust which isnt a big deal because im catless anyways and the downstream is essentially useless

Loki

iTrader: (1)

Cleaning and resetting the ESS (20-time brake pedal stomp procedure) isn't a bad idea. When you installed the intake, did you include the 2 flow straightener mesh screens as well? Usually intake problems show up at idle not at 6k, but never know.

My other thought is intake valves - SSV, APV, VDI. The APV is meant to open at 6250rpm, right where you're having issues. Normally you get a code if it doesn't work, but the APV is the trickiest to troubleshoot because it/they are way at the bottom of the lower intake manifold. If the problem showed up with the intake, I'd eliminate that as a possible cause before taking apart the intake.
You said it happens at WOT, but not at partial throttle?

travisinthe8

I have both of the mesh screens installed

I honestly cant remember when the problem started as ive been daily driving it this way for over a year….

just been suffering in silence 😭

The car ran perfect when i bought it unmolested

then i modified the car and it has issues

i have air pump delete as well

*edit* i did have SSV code at one point when i did the air pump delete but i solved that issue by purchacing a plug set and finding the one that fit snugly into the vaccum line and the code went away

Also i belive it only has issues at WOT but i exclusively drive this car at WOT because it begs to be beaten on. When im doing my warm up driving for the first 15mins i keep it well under 4k rpms and short shift with zero performance issues

could be a matter of the lower intake malfunctioning like you said, ive pulled them before on a buddys car only to find the most ungodly amount of carbon ive ever seen in my life

Loki

iTrader: (1)

Wait, what do you mean you plugged the SSV vacuum line?

travisinthe8

Okay so….

checking fuel trims, ive had it idling for about 10 mins

short term is around 0 - 2 %

long term has been chilling at 10.2% hasnt moved

travisinthe8

Im not sure what the vaccum line was, it was running from the air pump to what looks like a ssv solenoid under the upper intake so i plugged it like everyone says to do

travisinthe8

I know the picture says 10.2 but long term dropped to 8.6

Loki

iTrader: (1)

So you have a moderate vacuum leak. +10% long term trim means the ECU learned it needs to add 10% more fuel than is expected at the measured airflow, which means 10% more air is getting in somewhere that's not through the MAF sensor. +10 isn't the end of the world and I wouldn't expect it to cause your issues, but may be a clue. Look for cracked or open hoses or poorly mated MAF or intake manifold joints, and check out of sight under the throttle body especially.

So you plugged the output from the air pump solenoid, right?

travisinthe8

Yes i plugged the output from the air pump

thank you so much for your help, whats the best way to go about smoke testing for vaccum leaks?

cigar while the engines running?

travisinthe8

After searching around the engine bay ive found some hoses with light cracking, and most of the vaccum hoses look old and decrepid, im gonna buy a few feet of vaccum hose and replace everything i have access to, I will keep you updated on if this made any changes and ill post the fuel trims afterwards

TeamRX8

iTrader: (25)

you should test or replace all the check valves too

the check valve in the vacuum line between the UIM and the intake valve solenoid vacuum tank is especially important.
.

travisinthe8

the little valves that look like wategates?

travisinthe8

Well i solved some of the vaccum leak maybe?

its now 7.6% long term