Yet another stalling/rough idle thread after battery disconnect
 

Hi everyone,

I hope that this is really simple, and I did search and found a zillion replies that could be a zillion things. So hopefully I already know the answer. However there's a bit of backstory to this one that may be relevant.

I have an '05 RX8 GT that I (assume) I boosted backwards. Normally my jump-start kit auto detects the polarity and switches accordingly, however in this case the battery was completely dead (so no auto detect). Add to this I was tired, all wires are black, and the +/- symbols on the battery are completely covered by the clamps for the wires and although I'm 75% positive I did it correct let's assume that I boosted it backwards.

So the horn and headlights start going like mad. I disconnect and reconnect and this time the instrument panel goes on, headlights work, horn works, windshield wipers work, but nothing inside does.

Turns out I blew the master 120A fuse, radio fuse, and some random 15A fuse in the engine compartment. The 120A fuse is apparently a clear sign of a backwards boost, hence why I am acquiescing on that one.

Now even before this it took longer to start the car than it should (3-5 seconds), and apparently my ignition coils are shot (They have not been replaced in > 30K and 3 years). So I'm looking into that and will replace ASAP. Dealer wanted $1200 for coils, wires and plugs (latter 2 I did last year). I told them to take a hike.

However here's the root question: now the car stalls randomly when going from load to idle, and when it does it takes a good 6-12 seconds of cranking to get it started again.

I find it unlikely that boosting it backwards would have done anything else to the car, and I found several comments like these:

So is this likely the problem? I just have to wait for the ECU to re-learn what's going on?

Dealer told me that the problem was 99% because of the ignition coils, never mentioned anything about just giving it time to relearn. I managed to get it home by never letting it go under 2000rpm and by the time I parked it seemed to be ok. I haven't taken it on the highway yet or redlined it.

Should I just fire it up, keep the rpms up a bit until it warms up, then redline for a bit and let it go back to idle? I found a dozen different comments about things to do in this situation, but coupled with my poor coils (which I am replacing ASAP) what should I do?

Thanks for the help!!

Did you replace the battery?...if the battery is weak..it won't hold idle and it will die

You might also want to reset the ESS ( brake stomp) profile as well...

It will adapt after a bit...but it should still idle well enough not to die

Replace the coils ;) That is a no brainer on this car...

Hey thanks, yeah the battery was replaced. Very strange - was perfectly fine (or at least I had no problems with it). 2 days sitting and battery voltage < 7V and wouldn't hold a charge at all. Odd how quickly it finally died.

I haven't done the brake stomp thing, and I am looking to replace the coils. Considering that OEMs are $280 for the coils alone I might as well put in the extra $150 and get LS2 or $200 for the BHR coils with new wires while I'm at it.

Did they check the alternator output when you replaced the battery :)

Sounds like it shorted a couple of cells.....

Get the coils and then see what happens...FYI you can get the OEM ones for $35 here

http://www.rx8performance.com/collec...?q=Maintenance

Not as far as I know. Why does it sound like an alternator problem? Didn't think of that. I can get my normal mechanic to do a load test on it I suppose.

Thanks - those aren't OEM though:

A lot of people swear by the upgrades, citing 10-20% improved fuel economy even, so I might as well look at the upgrade. Not sure that I'd trust a component that's 1/2 the price of OEM :)

LOL...they are likely made in the same factory :)

I have installed the Intermotor ones in a couple of cars and they worked just as well as stock :)

Hi I just purchase a rx8... and when i start the car it hesitates for a bit and after it starts the Idle does not stay stable and the car turns off. but if i run the car for like 10 on the road it stops sometimes. can someone help me with this problem. i would really appreciated

Thank!

My problem was solved by just driving it through the RPMs and gears. Took about a half an hour of various driving conditions but now it's back to normal.

Not saying that this is the only way, but here's what I did:

- warmed it up by holding around 2000rpm (to avoid stalling)
- held it at every 1000rpm for 15 seconds three times returning to 1000rpm between (note that around 4-6krpm sputtered a bit)
- drove with my normal driving (heavy, WOT) on city streets
- drove in low gears (high RPM) on highway accelerating WOT when possible
- light driving on city streets back home
- re did the idling (at every 1000) test and this time was fine

Now the car runs like it used to. Still need to replace the coils though.

Did you test coils with napa coil tester?

i have not test the coils.. but i will and see what happens...
thank you!

Have been experiencing the same issue. It seems that the Mazda cars from our generation have this relearn procedure that works for every Mazda 2004-2010 owner. If you just connect the battery and just go, it won't work because it hasn't relearned everything. Maybe there is more to it than just a STFT and a LTFT.

It has been mentioned that you just let the car idle for 10-20 minutes with all accessories off, and then after those 10-20min you just turn your lights on, blow your AC on max power, turn on the seat heating and so on. I believe that the ECU can read what accessories are on, and adjust the fuel trims to those settings. In any case, this has worked for MANY people, and I will try the same soon as I have replaced my battery. Also, clean your throttle body, check for vacuum leaks and so on.