I posted this in the 3rd gen section but no one could give me a real clear answer. Hopefully you guys can help me here.

I can go from a dead stop and nail it through first and second gear. i see a max boost of 10psi and right at transition i see 11psi witch tappers down to 8 psi by redline. Now, the problem occures right around 5800rpms and or 6300rpms. During those RPM intervals i get about .5 seconds of ignition break up (assuming). The exhuast note changes almost like no spark is occuring, then the engine comes back to life and continues to climb up through 6000 and SOMETIMES makes it to redline, other times i get "breakup" around 6300 rpms.


Like i said before it happens around 5800rpms and sometimes around 6300rpms or vs versa. I changed the plugs with a fresh set and checked all relevant vaccum lines (shot in the dark). I ordered a grounding kit and im eyeballing a yellow top optima battery per some people say it sounds like a grounding problem. The thing i dont understand however is that if it WAS a grounding issue, would'nt it happen in every gear? In my case it only happens in 3rd gear and 4th(dunno about 5th but im guesing it does)!. HELP!

 

P.S mods are 3inch DP, stock Cat 3inch CB. Apexi intakes and hard pipes.

 

you need to log it. it is no way to dianos the problem on paper.

 

I have similar problem and thus suffer from top end power. I know my shitty exhaust is only like 2.25" and is crush bent just before the muffler (diameter like 1.5" only at that spot). I also changed my spark plugs and plug wires, did the grounding and yet I still get the misfiring. Hopefully full 3" exhaust will heal it or else I'm buying HKS TwinPower next.

BTW. What are your fuel mods ? I'm running M2 Stage3 ECU and its pig rich up top, which stock spark cant handle too well.

 

i have the stock ECU. still... im not adding anymore performance mods untill i can aford a PFC. witch looks like im going to have to get one so i can log wth is going on. grrr.

 

Are you sure your not hitting fuel cut. The stock ecu will falter if it is seeing boost above 10 psi...

 

Fuel cut is more than just a slight hesitation.

 

Changed your fuel filter lately? I don't think it would cause those symptoms, but you never know. Another thing is; how much oil is getting in the intake system. If its alot, it could be your turbos or pcv valve. Pcv valve would cause oil to be pushed out of the engine and into the intake tract just in front of the primary turbo. Too much oil can cause an overly "dirty" burn.

 

To much FUEL..

I had similar break up during my tuning.
My Tuner stated thats because it was to rich.
After the tune all of that stuff went away..
and haven't felt it since..

 

get an ecu, change your plugs.

 

I just got my car back from gotham...Well, this is very similar to what they spent all night diagnosing...First they couldn't tune becuase of the breakup above 5000rpm...

So the troubleshooting started...

1. replaced the plugs (Helped a little)
2. Installed new crank angle sensors
3. rewired the crank angle sensors directly to the PFC to eliminate any guessing wheter that section of the wiring harness was bad.
4. Replaced the trailing coil (it ohmed out at factory spec when it was cool but when heated it was much higher than factory spec.
5. changed from Magnecor wires (aparently the impedance on these are too high) and went with the NGK
5. installed race plugs ($33 a pop)

that all helped a bunch and then Steve went tuning again....The breakup was at 5500 and ever so slight...But still enough to make you worry...

So then he changed the distance between the crank angle sensors and the little wheel thingy on the main pully and that fixed it....

No one told me how hairy it gets when you start putting down bigger numbers....So much **** to watch. Anyway, hats off to the guys at gotham for staying up till almost 2am trouble shooting and tuning.

 

I have almost all the bolt-ons, and I used to get bad breakup from 5500-6000ish and up, all the way to redline. Not fun. I put on the HKS Twin Power Ignition Amp, and she pulled harder than ever before, right to redline, w/ no breakup. And I haven't even gotten it tuned yet

 

oh god... thats not what i wanted to hear. God knows i always end up replacing so much **** when im "guessing" what that the problem might be.. i would almost rather stuff just stop working period. That way you would be able to find the cause more easily. sigh.... im going to replace my fuel filter in a couple hours. ill let you guys know how that goes.

 

ok i just replaced the Fuel filter... still getting break up..


Question.. is it possible what im hearing isnt break up at all... but actually detonation? i know its hard for you guys to guess what the problem is over the internet... this problem is just kicking my ***.. :T

 

if u think its knock, u really need to stop driving and take it to a shop. 300$ for service is much cheaper than 4k for a new engine instal.

 

i agree.... But finding the actually problem myself is cheaper then paying someone else to :p..


Im going to buy a PFC and get off the stock ECU. also eyeballing an HKS twinpower.

 

Detonation sounds like shaking a tin can half filled with nails (no, not fingernails )

Did you also change your spark plug wires lately ?

 

wires have like 5K on them.

 

good advice, I hit the fuel cut twice on the stock turbos and that was the end of that motor, but 11psi is pretty low for a fuel cut, I could go all the way to 14.6 before i hit mine.

 

okay.. so. i have changed my plugs again. wires have 5K on them. ive replaced my fuel filter. ive tested the fuel pump. i installed a mazdaspeed grounding kit as well as cleaned up the stock grounds. but im STILL having the same damn prob. im thinking its more of a fuel problem now since it only has in second gear right at redline and in 3rd at 5800rpms or 6300 rpms. sigh.. im about to drop kick this car.

 

Similar thing happens to me in 3rd and 4th, WOT, sounds like the exhaust is sputtering. Sometimes it doesn't happen, and sometimes it goes away. Same RPM range as you're talking about too - mostly happens in 3rd though.

Sounds like a similar problem.

 

what mods do you have? mine only happens most of the time as well.

 

Test the leading coil

 

install a fuel pressure gague and go for a test drive also. only way to tell if the pressure is the prob.

 

I started getting high rpm break up right after I upgraded my Fuel Pump. Don't ask me why, but I did. I was also runnign the M2 Stage 3 ECU. I got an HKS twin power ignition amp and the hesitation was gone.