eyeoutthere

I am putting an S5 motor in my S4. The first time I hooked up the battery I put it in backwards (I assumed that the solid black wire was ground).

After I realized what I did, I checked all the fuses and found the “Body” (7.5A) fuse was blown and I replaced it.

Keep in mind that I was installing this engine for the first time and I hadn’t tried to start it before the battery incident.

All the lights and turn signals and junk work.

1st problem: None of the gauges or warning lights come on when I turn the ignition on. The only ones that work are the “door ajar”, and “trunk ajar” lights (they where in fact ajar); and the “Low coolant” light and buzzer came on a couple of times (I had just added coolant to it, so that is reasonable).

2nd problem: The car will start and run for about 4sec and then shut off. (This could be unrelated to the battery thing. I haven’t had a chance to take a good look for vacuum leaks, or check the AFM connection. I will do that when I get home.)

Where does the O2 sensor plug in on the S4 harness? The only connector I could find was one from under the air intake. Is that the correct one?

What do you guys think?

Thanks,
Jason

Fingers

you mighta cooked yer ecu :S

DiverseCC

yea sounds like an ECU, my one friend did that on an RX too

eyeoutthere

But the car runs. How could the car run if the ECU was cooked?

It seams like it would be pretty unlikely that only a section of it would be fried.

Because something has to be sending a pulse width to the injectors.

tmiked

Could be the fuel pump is just working when the starter is on. Check the wiring diagram. On some models there is a resistor for normal fuel pump operation. Something in this circuit could be blown.

CarmonColvin

I had this happen to an '87 Mazda 626GT I had. A friend put in the battery and I did not check its position before hooking up the cables. I went so far as to try and start it with it hooked up backwards.

Afterwards it needed:
New Starter
All new fuses
New ECU
And assorted light bulbs all over the car.

It was not easy to diagnose the ECU problem and it was NOT cheap.

sunshine

iTrader: (3)

First thing to check is the main engine fuse. the 100 rated one. It should be the middle one in the engine bay fuse box.

ViperKillerWannabe

It wouldn't even crank if the main engine fuse was blown. He says it actually runs for about 4 seconds before shutting off for no reason.

eyeoutthere

Well, I can pretty much rule-out all of that stuff except the ECU. All of my lights work, even the instrument illumination lights. The car cranks fine and starts (but only runs for 4sec). Besides, it doesn’t make any sense that filament light bulbs would blow because they don’t have polarity and won’t blow unless they get more than 12V across them; which is not going to happen unless Mazda used a fucked up illumination system in the 626 (which is entirely probable).

It doesn’t make sense for a car maker to produce a vehicle that self-destructs when it’s battery is installed backwards. I was never a fan of “idiot protection”; however, it is common practice for engineers to implement short circuit and reverse polarity protection measures on consumer electronics. It does not effect fit-form-and-function or increase cost by any significant amount, but it increases the reliability of the product.

Ok, back on track …
The only things that don’t work are my gauges end warning lights. Plus the fact that my engine won’t stay running.

I’m going to rig up something to check fuel pressure. Maybe the fuel pump is priming but not running when the car is started.

CarmonColvin

I agree that polarity should not effect light bulbs but I think the bulbs were blown with a surge of power caused when it was attempted to be started with the battery hooked up backwards. When the battery was hooked up nothing happened to my knowledge but when the key was turned the engine bay lit up with sparks (it was dark, lack of light was root of ill fated battery position).

SonicRaT

iTrader: (6)

Check that the AFM is plugged in & hooked up to the intact duct, that'll cause that

HAILERS

Ditto's. AFM fuel switch problem. What AFM are you using? Have you tried to jumper the fuel pump check connector? Yellow, right fender area, two socket outfit. Jumper it. Or read the manual at http://www.iluvmyrx7.com

What alternator are you using. S4 or S5? Small connector not on?? That would explain the idiot lights.

O2 connector under the intake. Shielded wire. WAS grey in color originaly. Might be light brown now. Single spade connector on the end.

mrb63083

iTrader: (4)

muahahaha i had something similar like this happen to me...


I had a friend accidently cross the terminals with some jumper cables one time. I replaced all the fuses. It wassn't my ecu or wireing harness, it was the trailing firing coils. They were burned up. Other than that, the only thing that got screwed up was the tachometer.

eyeoutthere

You are awesome.

New developments!

I am using the S4 AFM. It was not plugged in all the way, I plugged it in. That fixed the "only running for 4sec" problem.

Now it only runs for 1sec . With the AFM plugged in, the car will start but then immediately die. I can however rev it and get it to keep running; but it will not idle.

With the AFM unconnected, the car will idle for 4sec but will not rev or stay running.

I am using the s4 alt. As far as I know the small connector is plugged in, but I will check it again after I post this.

The car revs fine with the AFM connected (I keep trying to call it a MAF sensor ) So I assume it is not a fuel issue, but could you tell me more about this Fuel Pump Check connector? I just look for a Yellow, 2 terminal connector in the passenger's side? What does jumping it do? (my computer won't display that manual)

The O2 thing is taken care of, thanks.

Would the car rev good if the trailing coil was toast? Would it idle?

Thanks guys, I'll check some of this stuff out and get back to you.

ilike2eatricers

You may have a massive vaccuum leak. I was redoing my whole sound system in my car last weekend and my car wouldnt idle afterwards. Turned out to be a loose AFM, secured it properly and it ran perfect. It may not be electrically related. I assumed mine was after doing the stereo install but yea it wasnt.

jgrts20

check the main fuse under the hood, it probly needs replacing!!

chris

eyeoutthere

What is "The Main Fuse"?

I checked the under hood fuse box (the one with or so lard fuses in it) and they all looked good.

I found a 2 terminal yellow connector in front of the passenger’s side wheel well and I jumpered it. No luck there.

The plug in the back of the alt is plugged in. Should I test for a voltage on it?

I unplugged the trailing coils but it did not change the way the car ran.

I also disconnected the trailing coils on my roommates S5. It did not have the same symptoms as my car. It ran and idled fine.

My BAC is unplugged and it is not connected to the air intake (the tube that it connects to on the air intake is capped off). Will this cause any problems? The BAC should be closed when it is unplugged, right?

I have been looking for vacuum leaks but have not been able to find any. I will keep looking.

Anymore suggestions?
Thanks again guys.

HAILERS

The fuel pump check connector near the right hand strut tower is used for maintaince purposes only. It can be used to bypass the micro switch in the afm. If the car is running by keeping the pedal down....don't bother with the fuel pump check connector. That is not your problem.

The trail coils don't have to be working for the car to run. You'd never notice them not working...excep that the tachometer won't work unless the trail coils work. So..if the tach is working, you know the trail coil is working.

About idiot lights....they should come on if the engine is not running and the key is turned to the ON position. What happens there, is that the alternator puts a ground on a relay in the CPU which in turn makes a switch that feeds 12v to the idiot light cluster to turn all the lights on. Once the engine is running and the alternator is putting out,the ground I mentioned above....goes away and the relay in the CPU relaxes and the idiot lights go out. They will not come on again unless each individual light gets triggered from its source or the engine stops and the key is to the ON position.

The BAC'S whole purpose in life is to help maintain a 750rpm idle. If its not connected...it can't function. That said....the car should idle without the bac once the car is warmed up to running temps. There is a procedure for setting the idle. Its in the manual. It consists of setting the timing, then installing the initial set couplers jumper, screwing with the bac's air screw etc. You need to set the timing first.

Be careful about jumpering plugs. NEVER jumper the single bullet connectors on the lead or trail coil to ground. Bye, bye ECU if you do that.

eyeoutthere

Thanks,
I’ll reconnect the BAC tonight and see what happens.

HAILERS

Don't dismiss the bit about the vacuum leak. If its a large leak like from the lack of a line to the brake boosters feed line, that will take a lot of throttle to keep the car running.

If it's a small vac line or several small vac lines, it would take a bit of throttle to keep the car running, but nothing like the brake boost feed line off.

Also......after warming it up, try to check the timing for being spot on with a timing light.

MasteRX

You might make sure that all of the wiring is good to that AFM. On my car there is one wire that can pop loose out of the harness and when that happens, my car will only run for like 1 sec.

Project84

I did the same thing a couple weeks ago and had the exact same problems. I took out the ECU, opened it up to check the circuit board and you could see the burned black resistors and solder. Only thing I did different was I tried cranked the motor while the battery was hooked up backwards where as you didn't.

Codigo4

I have to admit, I wasn't paying attention, and I did the samething this last week. I hove three blow fuses in my fuse block inside the car, but my car is still apart, but I was checking other stuff and I think my ecu is cooked. Is it probably a good indication that the ecu is baked, because when I try checking the ecu codes my checker lights won't light up at all, they should light for 3 sec. before they flash any codes, right?

RETed

Check all fuses...
If that fails, you need to break out the DMM and electrical circuits and start digging around.
Troubleshooting electrical **** is a royal PITA.
We can't miraculously offer you a solution that will fix your problem.

If you're lucky, it just blew the 80A / 100A fuse under the hood.
If you're not, electrical components can blow up which include the stock ECU.


-Ted