satch

iTrader: (1)

You don't need the trailing coil to start the car.

satch

iTrader: (1)

How did you go about cleaning the ECU? Also, the coils ground by being mounted to the fender. Did you clean the spot where the bracket bolts to the fender to clean the grounds or perhaps something else?

RotaryRocket88

iTrader: (7)

How about the Vref voltage at the ECU? Have you checked that yet?

blackrotary23: your shameless thread jack has been removed. Make your own thread.

blackrotary23

i was just trying to help.

blackrotary23

i just wanted to post my results of the same problem so that the original poster of this thread could get some ideas from my car problems, thats all.

RotaryRocket88

iTrader: (7)

That's great, but the OP has an S4. S5 electronics are very different, and things like limp mode due to MOP failure don't exist. It just ends up making the thread confusing.

SirCygnus

iTrader: (1)

i dont know. my car would fire right up for 3 secconds and then die. im 150% sure of this as i did it on other peoples cars, and it would do this exact same procedure.

rev up to 3k rpms, then back down and dead.


just out of sheer curiosity, try it.

does the tach needle bounce? this was also a symptom. if it does not bounce, then there are no coils firing. remove it the afm, and see if the tach bounces.

point-blank

iTrader: (9)

I meant the grounds for the the ecu and coils (bolt on the block under the uim, and the spots where the coils bolt up to the fender)

The tach bounces the AFM attached, and with it disconnected.

SirCygnus

iTrader: (1)

check the coolant temp sensor on the back of the water pump housing. sometimes if you disconnect it and re connect it, a pin can be pushed out and not make contact, making the computer think the coolant temp is -40 and it will run ungodly rich.

point-blank

iTrader: (9)

I may as well try that too haha, although I didn't disconnect it

Got a volt meter today so I am going to start checking voltages

Can anyone tell me where ecu pin 2a is? haha

Thanks again for all your help guys!

satch

iTrader: (1)

You should look at the "Fuel and Emissions Control Section" of the FSM (link below) and it lists all the pin locations, their description as well as their values (volts). Pin 2A would be the middle plug, top right position (top row and farthest right). Should read about 5 volts w/key to on. This pin wire goes to 5 different engine sensors and you could read the value at any of these sensors which is much easier to do then going to the ECU. Depending on the year of your car, the Vref will be the Brown based wire and the TPS having 3 wires will have one of these wires so it could be measured there (w/key to on).

http://www.teamfc3s.org/main/factory...SYSTEMS_NA.pdf

point-blank

iTrader: (9)

So I can check the vref at the TPS?

also I feel kind of dumb for asking, but if I were to test the voltage at the ecu, I stick the positive probe of the multimeter into the back of the plug correct?

satch

iTrader: (1)

Yes, and the other terminal to a ground which you could use one of the ECU mounting bolts at the front of the ECU.

point-blank

iTrader: (9)

Is there any other places I can check voltages for the sensors? Instead of pulling my interior apart again? haha
If there is, what are they and which order do you recommend I test them in?

Thanks!

satch

iTrader: (1)

If the Vref is good at either the TPS, Pressure sensor, Variable Resistor, AFM, and Atmosheric Pressure sensor then then it is good at ECU.

blackrotary23

have you tried disconnecting the battery for 5-10 minutes to reset the system? trying wont hurt, it might help. i have seen it work a few times.

point-blank

iTrader: (9)

yeah haha thanks for the tip though

blackrotary23

well, i was told this: make sure that these three things are working before going into anymore detail...........fuel, air, spark.

if you are getting fuel, you would know it. the engine would be flooded when you take out your plugs to check it.

and you already know that you are getting airflow even if the maf if bad, it will still start but run crappy.

now for the spark: you know your trailing coil is working as long as your rpm needle is bouncing. also, if the needle bounces, you know that the main relay works as well. the coil might not be strong, but it is working enough to spark the fuel.

check the leading coil again.........i switched out mine and the car fired up. try the coil, try the coil, try the coil

oh yeah, and try the coil, lol.

SirCygnus

iTrader: (1)

no, it wont run crappy, it will start, do the 3k rpm warm up, then die. in that order if the afm is bad or busted.

point-blank

iTrader: (9)

ok so I tested, the brown and white wire at the tps read 4.9 volts
then at the pressure sensor it was also 4.9

I checked the resistances on my AFM and they were all in spec.

What now?

point-blank

iTrader: (9)

ok so no spark is the definite problem, any ideas on what it could bb

satch

iTrader: (1)

Check the CAS. Read post #29 in the link.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/could-i-have-fried-my-ecu-918831/page2/

point-blank

iTrader: (9)

ok I checked voltages per the FSM at the plug that goes into the ecu. I checked the leading coil, trailing coil and the CAS. The voltage readings for each coil were in spec, but the CAS was not.
In the FSM it says the voltage (CAS) is supposed to be >1v mine was at about 1.9v.


my internet crapped out last night so I had no access to the section of the fsm I needed, and now I have to work, so I will have to wait until tomorrow to check resistances on the plugs like you said in that other thread.

Thanks again for all the help guys! I don't know where I would be without you!

satch

iTrader: (1)

I think you mean less than one volt, and it actually should be closer to zero than 1 volt. The CAS does not put out any voltage unless it is spinning so with the key just to on and the large ECU plug disconnected your readings are a bit of a head scratcher. I'm thinking you may have taken the reading with the ECU plug connected to the ECU and were reading voltage feeding from the ECU perhaps, perhaps not.

rotarygod

iTrader: (1)

A bad afm can absolutely lead to no spark! It's not saying it always will as there is more than one thing that can go wrong with it but it most certainly can. I've actually had that particular failure. The afm may measure air but it still talks to the ecu which tells the coils to fire. This is not a thread jack. It is a relevant topic to this thread as I had a failed afm cause a no spark situation.

Back when that problem occurred about 15 years ago, I took the car to a Mazda dealership after a couple of weeks of nearly pulling my hair out. They told me that my coils must be bad. Both of them at the same time? I don't think so! They surmised that the cas burned them up. Um, not going to happen. Even a bad cas although not impossible, it highly improbable. Then they told me the ecu fried taking the cas and coils with it. They said repairs would be $2,000. Not satisfied with their answer I took my car back home. I replaced the ecu. Nothing happened. The coils, plugs,and plug wires had all been swapped out and wiring to the ecu was verified to be good. The only thing left to check was the afm. People insisted to me that the afm can not cause the coils not to fire. After staring at the schematic, I felt otherwise. I swapped out the afm and the car ran great. When I put a new intake on that car I pulled the connector too hard when trying to disconnect it and it severed a connection to the ecu. The ecu no longer sent the signal to the coils to fire.

I was going to check it first since I had just installed an intake but I was being told that it couldn't happen. They were wrong!