HELP!! Missfire :(

Sup guys,

Well over the past few weeks I've noticed some ignition issues at idle and some hesitation and "back pressure like" missfiring while driving but off the throttle.

It has gradually gotten worse and worse to where we replaced the spark plugs with 2 step cooler iridiums (remember my car's boosted) and hoped that'd fix the problem... Well it didn't and so I pulled my CEL codes and of course saw the first two and expected them (the VTCS code from the ECU swap and the Mil fix code, both of which I'll take care of tomorrow) but then came up the #300 code indicating a random missfire.

So the next step was to replace the coils... Did that... And same thing- only now it's gotten so bad to where I'll stall at every red light or stop sign. Basically anytime I drop under 1K... This makes for a pretty tough ride to work everyday.(headshake

So today I went and got the Magnecore 8.5 wires in hopes since it being the final piece of the iginition puzzle that it'd be the answer to my problems... But it wasn't. Instsalled them at the shop I got them at and stalled all the way home.

I'm starting to get frustrated becuase I feel like I've run out of options. I'm confident it's not a vacuum leak becuase I've traced all my vacuum lines and have tested them for holes, leaks, or rips. Same goes for the intercooler pipes and BOV hoses.

I've read on another thread that it could be the EGR valve gone bad but if that were the case I should've gotten an EGR CEL, correct?

Any advice would be great guys because I feel I'm at a dead end.(scratch)

what other mods do you have on the car besides the turbo kit? internal work (cams or anyting to do w/ altering the timing). is the timing dead on what it's supposed to be? just more things you can check out. hope you get it all sorted out.

you are having problems because of the new intercooler.

you might have to adjust a few things, because id imagine that you lengthened your charge piping a little, causing the idle to drop, enough for you to stall every time.

try slapping the old intercooler back on and see what happens.

a faulty/inop EGR valve will not cause you to stall all crazy like that also.


edit: try giving corky bell a call on monday and see what he says.

Actually it's not the new intercooler at all.... I have been having idle issues for a few weeks now and at least week or so before the new IC even went on. It's running super rich which is causing all the problems. I ran withthe new IC for two weeks with real problems at all even went on the rigourous mazdasports mountain run- with no real problesm... Then all of a sudden BAAAM the car is driving like shiz and stalling like crazy.

Beau is coming over tomorrow to help fix the problem. There's one of about 5 things it can be. We just need to rule them out one by one. Already ruled out is the iginition side of it. Now the O2's will be checked, the MIL eliminator added, and a thorough inspection of the vacuum lines and fuel system.


If it were the intercooler the car wouldn't have run so great with it for weeks and then out of the blue start running poor.

If you recently tapped into an O2 wire for tuning stuff (gauges, piggy-back) .. id bet that will be it.

Pe@ce

really? why would the O2 do that? and what can you do fix it?

hmmm well Id idn't really tap into any O2 wires... I just added a wideband O2 though. Didn't replace any of the other two, just added it with a third bung to give me a more accurate reading.

We're going to swap out O2's and see if that fixes the problem... If so- then we know I need to replace one or both. The only question I have (and the threads on ehre have conflicting information) is on if our two O2's are the same. Some say they're identical and some say the primary O2 (first one) is different and more expensive....

OK well if u didnt touch any stock ones im not sure. When I tapped my o2 for my a/f gauge i had really bad idle, to the point of stalling, until the sensor heated enough to start to read the ratio.

Pe@ce

well, if it's sourcing down to the 02 sensors a faulty one could very well tell the ECU to run in a "limp mode" so that may be the case. are any of the wideband o2 wires connected to the ECU in some way? checked all connections, made sure you tapped into the right locations and double checked the grounds? your primary o2 sensor will be more prime suspect as i don't have my rear o2 hooked up at this time (the car just runs a tad richer).

your fpr could be getting stuck open and causing you to run rich as a pig and it maybe time to clean that thing adn get seom new discs, i think you can order them from bell if thats it. or your o2 simulator went bad as well... i dunno i didnt read all the post cause i have to go back those are my guesses.

Problem solved.... It was the base fuel pressure- WAYYYYY too high.. Since I was running so rich it just rocked the spark plugs and caused missfire and BAD idle. The fuel pressure gauge I had used to set the base FP, after my intake fuel pump was installed, was setup wrong. So over a week or so it just had it's way with my spark plugs- and when I replaced them with iridiums 3 weeks ago it only took that amount of time (3 weeks) to completely fry those as well.

Right now I'm running standard NGK's until I can go get more iridiums. This time I'll treat them niceley.

Well out of this whole ordeal I've replaced all my plugs, wires, and coils so I shouldn't be hacing any ignition issues int he near future- and I now know what to do and what NOT to do as far as setting the FPR. Along with the wideband that I just installed the "safe" and "not safe" limits are etched into my brain and I know when to either adjust the FP or get off the throttle all together.(loser)