bad ecu?

[tomi240sx]

my car has been running for 1 year now and every now and then it would act funny. while I'm driving it the motor would die out and come back on, now it's running on safe mode. I'm trying to figure out if I have a bad ecu. my motor would start and idle at 1100 rpm( never got it tune). I figure I have a bad maf b/c when I unplug it, the idling stays the same. I check for power on the maf and I'm getting power and 3 ground. i have the s1 maf so i should be having 2 ground a power and a signal. my signal is showing ground. I cut my signal wire near the ecu and check my signal again at the ecu and I'm getting .02 on my voltmeter. my brother say I might have a bad ecu but I'm hoping he is wrong. I rewire my mafs( first time I didn't solder the foil to the shielded wire, now I did) because before when the motor would idle, everytime I grab the mafs wire, the motor would die. after I fixed the wiring the right way, it's been running like there is no mafs but the idle is constant at 1100 rpm. I tried resetting the ecu and changing the ecu with another one. both shows that I'm not getting power from the signal wire. I've searched for 1 week already b/c I want to make sure that I didn't miss anything but I didn't find anything. I checked on all my ground on the ecu and they're good. does the signal wire have anything to do with any of the 2 relays? please help. I got my car started and running because of this forum especially from jon powell. I'm asking for help again. this is my only ride to and from work. I just need to know if I have to buy another ecu. thanks ahead.

[gawdzilla]

a maf thats on its way out/dying can cause the exact symptom you describe.. try a new one

[tomi240sx]

just wondering if bad mafs then why I'm only getting .02 volt on my signal wire near the ecu. does the mafs have anything to do with any of the relays. I used to hear a clicking noise on the driver side when my eccs relay is on but now nothing. when i checked for power on the relay, all of them, even my ground is getting power. just wondering if bad wiring can do anything with this. thanks for helping me out.

[Darius]

.02V is a very weak signal if it even counts as one. If you have continuity between your signal wire and ground, that is your problem. The wire is shorted out. Start with the wiring first because it is free. Make sure you have continuity on all four wires, then check the MAF.

When you say your car idles at 1100 rpm, is that all the time or just when this problem arises? You shouldn't be idling this high. FSM says stock idle is 650 rpm. Have you ever checked your timing because idle increases with advance in timing. When I timed my motor back, I was idling at 1000 rpm and 20 degrees advanced. You could be further out than that. Now it idles at 650 rpm at 15 degrees of advance. I might have to bump the idle up a tiny bit for the cams I'm running but other than that, it runs well so far.

Check those two or three things and let us know what you find.

[tomi240sx]

I have continuity on all the wires on the mafs even the signal wire and ground that are shielded. did you say that this could be the problem? Please teach me b/c my older brother who owns a performance shop doesn't want to help me out. I think my car is idling b/c of not just my timing but also b/c of the tps, my cousin moved it and we haven't fixed it yet. I read up on that but not sure if I did it right. do I have to rewire the mafs wires again? please help, this sucks (especially when my brother is a master mechanic and don't want to help me, even when I offered to pay.) thanks in advance.

[tomi240sx]

I don't think it has anything to do with the mafs b/c I'm not getting power from my signal wire. I figure that it has to do with the ecu or wiring. can someone correct me know if I'm wrong. I'm thinking about redoing my whole harness. It have to be a short somewhere. please let me know if I'm going in the wrong direction. thanks

[tomi240sx]

I've checked my voltage for my relays and I'm getting 11.4v on all except b/w. how is the orange wire have power when it is suppose to be ground. I've traced the wire back to the ecu and it's not touching anything. Do I have a bad relay socket?

[Darius]

If memory serves me right, when I was troubleshooting my electrical gremlin the orange wire to the ECU is grounded internally by the ECU, so yes you should have power there. My ECU wasn't grounding it, so when I manually grounded the orange, it started right up. I think you are fine there.

Did you say you had continuity between your signal wire and ground or that both are continuous separately? If they individually have continuity to where they are supposed to have continuity, then don't worry about your wiring harness. I would look first at timing the motor properly and then at the TPS. If I remember, you time the motor with the TPS unplugged.

[tomi240sx]

yes I had continuity seperately on each wire. I'm just trying to figure out why I don't have any power on my signal wire for my mafs. I tried to reset the ecu and nothing. when I checked timing I did unplug the both tps just in case I did unplug the wrong one. I just don't understand why one day my motor would run normal and then the next day running on limp(safe) mode. I never really got to finish my wiring. my relays were tapped so that I could get the motor running and out of my cousin garage. that was 1 year ago. I'm gonna redo/recheck my wiring to make sure it's not that. what voltage am I suppose to get on the relays? 12v on all three except for b/w or less than 12v. thanks darius for your time.

[Darius]

I think that sounds right, but check the manual to be sure about the relays. There is a little section on how to test the IGN and ECCU relays.

Do you have spark? Are you positive?? It boils down to fuel or spark and if you can narrow it down to one or the other, it will make trouble shooting a lot easier.

[tomi240sx]

yes I have spark and fuel, if I don't have any of these then the motor wouldn't run at all right? it's just running on limp mode and when I check for voltage on my signal wire, I get nothing. do you happen to know what does a recirc relay do? I't located next to the fuel pump relay by the driver foot. one of my relays used to click but not anymore. just checking. thanks