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Discussion Starter · #1 ·
Ok, so here goes...

I finally found time to finish the atx-mtx swap and get it going. I put in a 93 mtx ecu, it started, ran good, but threw 4 codes.

16 - EGR
25 - FPR circuit
41 - VRIS #1
69 - Coolant Temp sensor

Now I researched these codes, and found 69 was a 93 specific code for a sensor not found in later years, mine is a 94. So I figure, put the atx ecu in, one, maybe more codes down. I put in the atx ecu. It starts up, the exhaust reeks of gas, and idles for about 15 seconds then gradually the rpms go down until it dies. CEL light went on, check the codes, the same as above minus the 69 code.

Now I wonder why the 93 ecu ran the car fine except the codes, and the atx ecu ran it horribly rich? FYI, all of those codes that were set, I did not touch anything relating to that when I did the swap... So what gives?? Do these things go bad from just sitting for a while?

I wonder if the front connection of manifold-front being slightly loose has something to do with it? I was putting on the front pipe, and one of the studs snapped off the manifold. I may have to drill out that stud and replace it with something... Boooo...
 

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code 69 is probably coming up because your car is a 94 meaning is does not have the extra coolant temp sensor the 93's had, and since you are running a 93 ecu it is probably looking for the sensor which your motor doesnt have. maybe try a 94 MTX ecu if you have one available. for the stud you snapped off maybe try putting in another gasket, that should seal it up but it might not last. im not sure what to make of your other issue
 

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Discussion Starter · #3 ·
code 69 is probably coming up because your car is a 94 meaning is does not have the extra coolant temp sensor the 93's had, and since you are running a 93 ecu it is probably looking for the sensor which your motor doesnt have. maybe try a 94 MTX ecu if you have one available. for the stud you snapped off maybe try putting in another gasket, that should seal it up but it might not last. im not sure what to make of your other issue
Thanks for the reply. I realize that the 93 ecu is looking for that sensor, that's why I tried the 94 atx ecu. I just can't understand why all these codes popped up now when before the swap the car was running like a dream... No codes, no foul smelling exhaust, ran super smooth aside from the atx problems... I'm at a loss right now. I'm gonna hack away at that broken stud, hell, I may just drill them all out and put some grade 10 nuts and bolts in their place. I'll see how it goes. Keep the suggestions coming.
 

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Hmmm that is a bit strange that the auto ECU makes it do that.

Tried resetting the atx ECU at all? It could be storing running info for the atx or something.
 

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Discussion Starter · #5 ·
Hmmm that is a bit strange that the auto ECU makes it do that.

Tried resetting the atx ECU at all? It could be storing running info for the atx or something.
The only way I know to reset the ecu is having it unplugged for a bit. It was, for about 3 months lol...

I'm gonna check over grounds and connections today. I just can't see why the car is acting up now when it was perfectly fine before... :confused:

It's too damn cold to stay out there for a whole day... :(
 

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Discussion Starter · #6 ·
Ok, I took off the intake assembly to check my connections and such. There are 4 harnesses not connected. I can account for 3 (2 atx connectors, 1 neutral ss from mtx tranny), the 4th one is a 2 prong plug with a red and tan wire coming from it. I can't remember if this is from the atx or not. The egr plug is in and secure, and all grounds and vacuum hoses are connected. I tried running the car with only the intake pipe and maf connected, and it ran for a substantially longer time than with the filter on, but eventually to stall out like before... I'm starting to think the ecu might be the culprit of the idling issue...
 

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Discussion Starter · #7 ·
Ok here's a question for those that have done the swap. I have a strange feeling I'm gonna feel stupid if I get the answer I'm regretting...

Those of you that have done this swap, have you left the atx computer in? I mean plugged in and untouched? I have a strange hunch that the wiring that I thought was identical to an mtx may have wires going to the atx computer.

The reason I think this is that going over the haynes manual wiring diagrams, I saw that the egr position sensor goes to the atx computer, from there, I don't know. I wonder if all these retarded issues are because of something so simple like pulling out the atx computer?? :shrug:

I would try it, but I have my front pipe off in process of removing all old exhaust manifold studs (I broke a few lol)

Thanks.
 

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I'm fairly certain that you should remove the atx computer lol.

I read it in another thread here not long ago. Think about it though, why would you need it with a manual transmission :p
 

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Discussion Starter · #9 ·
I'm fairly certain that you should remove the atx computer lol.

I read it in another thread here not long ago. Think about it though, why would you need it with a manual transmission :p
That's exactly what I thought... I'm just wondering if a ground isolation has occurred by removing that pcm?? I'm still racking my brain as to why the car won't idle now, when there was no issues before...
 

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Discussion Starter · #10 ·
Quick update...

I have remedied the 25 and 41 codes. Turns out the vaccuum solenoids went bad?? Weird, but it worked.

The car idles nicely now, I had to turn the idle screw in a touch becuase the idle was rough and really low (~350 rpm). At least it idles though. No I have to rectify the egr (code 16) problems. I hope it's just the position sensor, I can grab one from the wreckers.

So thanks for all the help, it's slowly getting sorted out! :cool:
 

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does anyone know if you have to disconnect anything before removing the ecu? Im suspecting mine is faulty and have another one just wondering if there was anything else to disconnect then the battery.
 

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Discussion Starter · #12 ·
does anyone know if you have to disconnect anything before removing the ecu? Im suspecting mine is faulty and have another one just wondering if there was anything else to disconnect then the battery.
Even though you just jacked my thread lol...

As far as I know, only the battery has to be disconnected.
 
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