Multi part question/story looking for opinions.

First - can I buy I used ECU rather than a new one for $1000 (which I was told needed to be programmed for additional cost). Does the used one need to be programmed (and is California emissions an issue since I live in NY and may have been same emission as CA)?

The story -

My '04 MT was stalling out often, and after bringing to a dealer, was told I needed
a new engine.

I ended up bringing it to a friend of a friend's shop that has done rotary engine previously, to save a significant amount of money (plus I wanted to replace hoses, spark plugs and anything else that made sense to do while the engine was out - which was all included in his install price.) He also thought he could clean the throttle body rather than replace as the dealer wanted to.

The shop ended up getting the Mazda reman engine from a dealer in his state, close by, rather than the diagnosing dealer.

He installed the engine, and now the car still has the same issues (and codes- I think he mentioned #2 rotor) and he says the ECU is the problem and thinks the original engine was actually okay.

Any thoughts?

 

Moved to Tech. General Automotive is for NON RX-8 topics.


It's probably not the ECU. The chain of events from the dealer is too often seen, sadly. "Replace the throttle body" is something dealers go to ALL the time, and they only rarely fail. You probably have a very simple solution, likely ignition, grounding, vacuum leak, MAF or O2 sensor failure, or a fuel pump failure.


But, to answer your specific question, as long as you get an ECU for a 2004-2005 manual transmission RX-8, then you shouldn't have any problems with it. Other transmissions will cause problems, 2006+ might cause problems.

You will need to have the ECU coded to the car, AND every other electronic's module coded to the ECU. It's not going to be cheap and it's not something you can work around. They are all interlinked and won't work unless properly paired.

 

RIWWP - thanks so much for the quick response. I will trust your input even though you have so few posts!!!

ALSO- The shop owner had heard that a partially weak battery can cause wear on the seals when cranking. Has anyone ever heard of this?

 

I think it's time for a new shop. Let's start from scratch, what were the issues you started with?
While the engine was out, were ignition coils replaced?

 

I have never replaced a TB on a RX8, its not very common.

- If the engine was gone, did they supply compression test results?
- Did the dealer perform a vacuum voltage test?
- What codes do you have?

 

That shop owner has probably heard all sorts of things about rotaries that are not in the least bit accurate. This would be one of them.

A weak battery increases the risk of flooding by not providing enough power to the starter to spin the starter faster. Slower starter speed = lower compression = harder time starting.

The starter speed doesn't have any impact on the seals's wear.

 

This should never be a benchmark for knowledge

 

Goodwrench, I moved your post here: https://www.rx8club.com/series-i-tec...-track-246458/

 

Starter does not kill/wear engine's internals (seals, etc)

it does effect how good your engine starts though, faster spinning speed = easier to fire.

a Weak battery does effect startup, but it's the same for all cars. not just Rx-8, and no it will not kill your seals.

for the ECU, I never tried to program (rewrite) an used ECU, but I do know Mazda's IDS have this function which will be able to Force write a ECU, as long as you have the AS-Build Data from Mazda, last I checked and it cost like 30-40 bux to get that.

with that you can force write the newest calibration to any ECU (compatible model it is), but your issue does not sound like it's ECU related, it COULD be Engine Harness related though. I had my Engine harness replaced under warranty because of that(intermittent short, which causes some weird issue)they found it when they replace my engine, wiggle the wire around and the readings on IDS goes wild.

and that harness cost a good thousand bucks if you buy new. if mine goes bad again for whatever reasons, Might as well rip the old one out, send it off to a place that I know and build a new one with much better material that will never be killed by heat.

they replaced my Throttle Body at the same time, cuz mine has already failed, just for some reason did not trigger a CEL. explains why I have crazy LTFT, again.

Have you replaced any of the coils, sparks ? oh by the way you might want to clean some of the grounding points as well

I wont be back for another few months, otherwise I can check for you

 

Hi Jackson,

Thanks for responding.

I passed along RIWWP's suggestions on what to check. The shop told me they checked all the grounding points and they are good.

The wiring harness is a good idea as well. There were a few times I had an intermittant condition where if I turned the wheel hard to the left while parking the power would cut out momentarily, but haven't seen that issue in a while.

The used ECU's are cheap enough I will by one on ebay and send it to him to check out. Now I have to try and get the compression test from the dealer that told me my original engine was no good.

 

That is an electrical problem, typically a battery ground.

The electrically assisted steering is pulling the most amount of power at low speed, and an unstable or weak connection (usually at the battery terminals due to exposure and corrosion) will be demanding more power through the connection than the connection can now support, and something electrical will cut out.

Usually it's something that is high load demand, like electric power assist, headlights, or fans. Sometimes it's instead something sensitive to voltage fluctuations, like the gauge cluster. In theory, the ECU falls under the 2nd category, and could lose input sensor data and/or be unable to issue output commands.

 

I ordered a used ECU from an 04 MT and the shop and programmer are saying they can't program it and what they read I have to have a new blank ECU. Is there any tip to wiping or rewriting the old ECU?

Thanks in advance.

 

Hmm, I don't believe you have to wipe the wold one? I think all they have to do is reflash the 'as built' data on it.

 

you need to put your cars "as built" data, along with the transponder data and stuff onto any new ecu you get, doesn't matter if its used or new

 

Yep you need to pay I think 30-40 bux to Mazda tech web site to get access to As built Data, then you can Force write it. Assume the ECU is the same year model I had the subscription before but it expired otherwise I can give you your As-Build data when you gimme your VIN number.

I have the system and know how it works. dealership will charge you at least an hour + whatever bullshit they can think of.