Hello, I'm not a mechanic, just a huge fan of the car and I'm on my second S. I've done a lot of voluntary repairs to the car but also have been plagued by Check Engine light issues since I bought the car in March of 2008. The CEL's have brought codes 1526, 1540 and P0305 (misfire). To resolve, I've had a MazdaSpeed dealer replacevacuum tees, O2 sensor, ABV Solenoid Valve, spark plugs (changed out Champions that were in car at purchase with Mazda parts), and #3 cylinder Ignition Coil. Now, still getting misfire code and always in cylinder 5. Dealer has moved fuel injectors, coils and spark plugs and code is now always cylinder 5. They've checked all wiring to coils, etc., and say it's all okay. So, they have concludedit's the PCM and when they put a signal to the fuel injector independent of the PCM, they say the injector is firing fine. They want $1800 for the PCM and $300-$400 "to install and program". First, any thoughts on if this is a likely cause, second, anyone know how to get this part for less than $1800, and finally, is this a job I can do myself? I've changed a starter motor in an old Toyota and am technical enough to figure out a service manual (but I don't have the service manual). Appreciate everyone's help. Michael Gust, Dyer, IN

 

Firstly, my frame of reference is the normally aspirated Millenia 2.5 V6. That said, one of the very few 'faults' that I've had with mine , (other than the failure of internal door light switches which are at least dirt cheap) these past 12 years has been with the ignition leads which carry the HT kilovolts from the coil to the sparkplugs. The symptom experienced was a suddenly occuring misfire/hesitancy followed by an engine shut down (possibly as the ECU detected a huge Kvignition spike as the lead broke down under electrical stress and shutting down the enginethus preventing unburnt fuel contaminating the cat).
Please note that all original leadswere within spec.on a low voltageresistance check using a digital multimeter. This is not an adequate check for intermittency only a full open-circuit so I bought a full set of leads from my Mazda dealer for very little money and replaced them singly (as I wanted to know exactly which one[s] were at fault) until I found the onewhich was breaking down under high voltage stressing. Problem solved. Personally I don't regard this as a 'fault' per se as ignition leads are a 'consumable item' in my book. Ifthe leads on yourshaven't been replaced (I'm presuming the 'S' supercharged doesn't have individual coils sited on theplugs) then it's worth a gamble with such a large amount of money at stake. Hope this helps, let me know if it sort's it out. Final though, You might like to try and get a set of leads on sale or return seeing as how you have spent so much money with your local dealer. Yuletide greeting folks ;0)

 

yo, the 2.3 mc motor dont have no hi tension wires or conventional ignition distributor. it has coil on plug system.

just curious, how do you know the dealer has really switched out coils and fuel injectors? i have done both a few times, and it is labor intensive. esp #5 cyl, which is the MOST difficult to get at. to change out injectors, the entire intake has to come off. what codes are there? and, if there was a missfire code for #5, why did they change out coil #3? also, what year? the 95-96 has a 4 pin coil, and the later has 3 pin. you can use the 4 pin in place of the 3, but not vice versa. the pcm lives behind the radio. kinda pita to get at, mainly because of the multi pin connectors. pull the radio, you will see it.