I replaced the ECU today, and after I replaced the ECU, my air pump is now working, which is great HOWEVER.... the ECU I installed appears to have another INTERMITTENT problem with the RPM's jumping to about 3k , then back to 1k consistently!!!! Im SURE I connected everything right... is anybody selling another used ECU NON-California 5 speed and Please with no KNOWN problems??? for CHEAP??? maby a 94 ECU or if anybody knows whats wrong please help....

 

Your chances of getting two defective ECUs are slim. Have you gone through the standard idle adjustment procedures?

 

The problem is that the idle bouncing is only intermittently it will act normal half the time, then out of nowhere start bouncing between 1k-3k rpm. My old ecu never had any Drivability problems at all. I only replaced it because my air pump wasnt working. Now the air pump IS working with the new ecu, but it has this new problem...How do I adjust the idle? does the idle have to be adjusted whenever the ecu is replaced?

 

I'm wondering if the ECU is fine, and the fact that you've got the airpump working has uncovered a new problem.

 

I was thinking the same thing, but I crossed that off the list of possiblitities already because I pulled out the fuse for the air pump to STOP it from working, and the idle still has the same intermittent bouncing problem I never had with my old ecu...... this is so confusing....

 

Have you had a professional look at the car?

 

yes I have and they said the ecu is bad. Get this..... JUST NOW I installed my OLD ecu, and the idle and eveything seems to be fine with no drivability problems what so ever. The only difference is that again my air pump is not working. So basically.... with my old ECU, there are NO drivability problems, but the air pump does NOT work, and with my new ECU, there ARE drivability problems, but my air pump DOES work.... its obvious I need another "good" ecu.......

 

Are all the connector pins on the ECU clean and straight? The pins might be covered in funk causing an intermittent connection/voltage fluctuation on one of the inputs or outputs.

 

I checked the ecu's connectors, and all of them seem to be fine. Its a little dirty, but definitley no sludge build up or anything that would cause a problem. The problem must be internal, because after removing the ecu I just bought, I installed the old one back in my car, everything runs fine again, but of course the air pump isnt working obviously. GOOD news is that I know now for a FACT that the air pump isnt working because of a defective ECU, now my solution is to find another ecu that actually will fix this problem, but not cause new ones!

 

What number is on the ECU? Are you certain it's a US 5-speed ecu?

Here's some of the ECU prefixes -

'93
N3A1 - Fed MT
N3A2 - Fed AT
N3A3 (ends in 881A) - Cali MT
N3A4 (ends in 881A) - Cali AT

'94
N3C1 - Fed MT
N3C2 - Fed AT
N3A3 (ends in 881B) - Cali MT
N3A4 (ends in 881C) - Cali MT

What number is it? If it's a JDM ECU, it could be kicking the 3000 RPM startup in, as that pin is used for a different feature on the JDM ECU's.

Also, what number is your old ECU? And, are you SURE you have a non-California car? I think if you register your VIN with Mazda it will tell you for sure. Or, just look to see if you have the extra sensor switch deal on the EGR valve.

Dale

 

My ecu is actually a N3A1. The one I bought is a N3A7. I think this may be the reason why I am having problems with it. I think N3A7 is made for a 1995 RX7? Anyway, either it was defective, or just the wrong ecu altogether, im gonna buy another ecu to match my exact specs of my old "working" ecu, and continue from that point

 

Have you tried adjusting your TPS?

Dennis,

 

my TPS, was already adjusted properly by Mazda last year actually, and I am not gonna toach my TPS, I had a bad experinece with that already!! lol The TPS and idle air control vale should never have to be adjusted, unless they were messed with, which they were not. thank for the help though, I know what I need to do.