AP midpiep, hard intermittent start?
 

Recently got a Agency Power midpipe dual resonator to go with my greddy catback. Works awesome, and is loud!
Car would start normally, then it would throw a cel. When cel was thrown, it threw the o2 sensor code. Then I have intermittent problems starting - almost sounds like my starter. When turn key, it is very quiet and sounds like its trying to get enough amps to turn over, then gradually gets louder and starts.

Any suggestions why it sounds like its dragging? Does the car need to be re-tuned at mazda????

Thanks in advance :)

You removed the catalytic converter... so of course you're going to get a CEL.
The rear O2 sensor is there to monitor the cat's efficiency... which is telling you there is now a "problem".

If you have an '04 or early '05, then you likely need an upgraded starter and new battery (if still OEM).
Its a common problem with those years.

I am aware that I will get a CEL. I am being informative with step by step of what has happened. My point is that why am I getting intermittent 'weak' start 'after' I installed the midpipe??

I have had the alternator, battery and starter checked....all came back OK. My starter is the original, and my year is 2005. Even though the test ranked ok, can this still be the problem?

I am fairly mechanically minded, but this is throwing confusion at me.

This is commonly misunderstood...
The starter motor itself is "fine" so it'll test OK unless there is actually something wrong.
The upgraded starter has a larger motor and can hold up better to the demands.
Just curious... what brand battery do you have and how many crank amps?

Sounds like a week battery to me. Did they do a "Load Test" on the battery after recharging it fully? Or did they just put a volt meter across the terminals and see 12+ volts?

And Mazda has NO way of retuning your car.

The o2 sensor tells the engine how much fuel to send into the engine. If it's broken it could tell the fuel injection system not to send enough fuel. Unfortunately, I can't totally rule out the fuel pump. The symptoms are very similar as they're both fuel starvation problems.

Thanks for all the replies...I have factory starter and regards to cranking amps, I was told the starter was normal. My battery has 640 cranking amps and with a load test, its in good condition.

I put the cat back on and it starts up normal everytime now. I dont understand. When I put the midpipe on, its symptoms that would send me to the starter or whatnot, but that test came back ok..............maybe its on its way out?

I appreciate all the replies..........

FYI... comparison of the original and upgraded starter:
http://www.vimeo.com/3653485