Hey everyone,

​​​​​​Today was the day that I was supposed to move my 7 to a new storage location. I made a post about how I haven't driven it for 2+ years as it sat in my storage. I tried to start it after charging the battery and it fired up, jumped to 3k rpm and died after 3 seconds. I saw that the fuel was low. In addition there was a huge gas cloud coming out of the exhaust when it started. I could do this multiple times and it would always die even when I tried to hold the gas pedal. The cloud of gas was huge.

I came back today and filled about 14L of gas into it. I removed the plugs and cranked her without the EGI fuse to clear any fuel stuck inside. I checked for even pulses and everything was good. I put a little bit of oil into each spark plug hole to build compression.

I then cranked her over without the EGI fuse to get it all around. I then put the EGI fuse back in and fired her up. She started better, not jumping to 3k but then eventually died even holding the throttle again...

So I gave up and decided to push her out of my storage unit so I could get her towed to my place and I can look at her there instead of the middle of the night with freezing rain in a storage facility. Then I realized the hill at the entrance was huge so I had to start her up and slam it into drive and try to at least make it past the gate. It died on the hill. I tried again and I got it outside, then it died again. So I looked around for any issues, any disconnected hoses or plugs. Nothing. The only way it moves was over 3000rpm and anything 2000 or below you can feel it almost trying to die before it just died no matter what.

I then had an idea to try and unplug the MAF and see what happens. She idles but it's rough and backfiring. I can put it in drive and drive for about 1 min but then it dies. I never went past 2000 rpm.

She is getting spark, definitely getting fuel as it is super rich, and is getting air... So what gives? Is the MAF bad? I tried to adjust the idle screw on the top while it was running poorly with the MAF unplugged and it did ZERO. I plugged the MAF back in and it died right away....

Should I look into a replacement MAF? I don't have any spares and not super great with a multimeter although I am practicing as of late. Does the MAF just die from sitting? The throttle body butterflies still move as well as I can hear them moving with the car off. Will unplugging the MAF cause damage? I only ran it minimally before I just pushed her.

Any other ideas? I am getting her towed to me in the morning as I managed to push her into a parking lot.

Question that may or may not be related, why was the "hold" light flashing when cranking her? I don't think it ever did that before.

Thanks for the help everyone!

 

Checked the codes and it showed codes: 8 and 10 for the AFM and Intake Thermosensor.

 

I'd check the wiring going to the MAF. It could be the MAF is bad, but before spending on it make sure it isn't something else.

The intake thermosensor is in the MAF which is what makes me suspicious of the wiring or the connector. This is how you check the MAF itself:



You can also use that information to check the harness. Both E2 pins should connect to ground with minimal resistance, and VC should be around 5V with key to IGN.

 

Yup. Check your wiring first. Might have had a mouse chew on your wires. Had a squirrel a couple years ago that got a taste for fuel injector wires. It disabled two vehicles

 

I'll check the MAF when I get home. I had to get her towed home as I tried everything in the parking lot and took the intake box off and took the MAF out. Everything moved freely.

What if it is a little higher or lower than spec?

What are the chances that an animal ate a wire? I did a quick look over the wiring and everything looks fine, no other signs of damage. The plug looks good and nothing is frayed. It just is weird that something would fail without any movement or damage.

 

It's just one of those things. Both the MAF and the thermosensor inside it use the same ground. If they are both not working, something may be preventing the ground from making contact and causing a common mode failure. Could be a corrosion issue, could be an animal issue, might just be a worn out and broken wire. Test the simple solutions before doing the complex and expensive ones

 

I don't know, I've never even seen one out of spec. I did have a MAF that went bad while being technically in-spec, but I would think that is the least likely explanation for your issue. Both the intake sensor and MAF being out at the same time really screams wiring problem to me. They're basically separate systems that just happen to live in the same plastic housing and share a ground.

It's hard to say. Really depends on how it was stored. They might have even eaten a wire under the dash, or under the ECU kick-plate.

My thoughts exactly. The MAFs are fairly simple and reliable, and parts aren't as easy to find as they used to be. Better to rule out any other issues before buying a new one.

 

Alright so I tested the MAF as I already had it inside and I tested it at room temperature and these were the results:

398 - E2-VS (Closed)
80-90 - bounces E2-VS (Open)
280 - E2-VC (Closed)
280 - E2-VC (Open)
1200-1800 - it changed everytime I tested it E2-THA (Room temperature)

These readings were tested with the MAF plunger fully closed and fully open as per the sheet provided above.

Does this look normal for a bench test?

 

The bounces on E2-VS don't seem too unusual to me. It's a small oscillation and the MAFs are sensitive, maybe the cone was moving a tiny bit when the reading was taken.

The E2-THA reading seems a bit fishy to me. That would indicate the temperature bouncing between 20C and 40C, and unless it's a lot sunnier in Hamilton than here it shouldn't be 40C out.

I would check everything again, and make sure the pins are clean so the multimeter probes get good contact. Just to be sure. Did you have a chance to check the harness pins yet? You should see grounds on E2, and 5V on VS. You can also go to the ECU and check the resistance over the VC and THA wires to make sure there's a connection, and use the FSM procedure to check the relevant pins on the ECU:






When I had the stock ECU I usually found the best way to diagnose issues was to start at the ECU. My test-lamp never indicated any trouble codes (even if I disconnected a sensor while the engine was running), but back-probing the ECU gives you direct feedback on what the ECU is seeing. These readings will account for any resistance in the wires too, since a reading can be in-spec at the sensor but then the added resistance of a bad wire puts it out of spec before it reaches the ECU.

While we're on the topic, if anyone knows what 2J does let me know. My S4 doesn't have it.

 

What about the E2-VC? It doesn't move when it is open or closed.

I have the MAF inside as it was pouring out last night so I did not get a chance to check the connector yet. I'll probably do it tomorrow as it's still raining today. I'll end up checking both ends of the wiring.

Can you use a regular multimeter for checking the ECU? Also, it says to check while idling but I can't do that so what should I do?

Thanks again for all your help.

Edit: I found a couple of threads here and other sites that say that it is either the wiring or MAF that is bad because apparently the car starts with a "pre-determined" setting for air and fuel etc and once the car starts it does it for 2 seconds and then switches to the MAF readings and if there is an error it sends a signal to cut off the fuel/spark/etc. This includes if it senses the MAF is malfunctioning.

 

if you turned the key on with the AFM unplugged it will set those two codes. most of the codes only set if there are open or short circuits.

 

So I had a quick chance to test the plug the same way as the MAF and these are the results:

Plug test
E2 outer - VS 1247
E2 Inner - VS 1221
E2 outer - VC 197
E2 Inner - VC 0
E2 outer - THA 1926
E2 Inner - THA 1765
Key off MAF unplugged

​​​​​​VC to a random ground on the car is 7.7 with the car key to the on position.

​​​​​Outer ground 0.3-0.9 changes and usually settles at 0.3 Inner ground 0

 

The first few numbers you provided won't be needed for diagnostics. It basically just means you're measuring across some ECU pins. The numbers that will most likely matter for this are the resistance from either of the ground pins to a body ground (strut mount or something) and the voltage at the VC pin with the ignition to on.

So to check VC, put the multimeter in DC volts mode. Put the key to IGN. Touch the red probe to the VC pin on the disconnected MAF connector, and the black probe to a body ground. You should see about 5V. You can also check with the black probe to one of the two E2 pins and it should still be near 5V.

If you get something like 3V or 7V, then you have an issue. Or if it's jumping around.

It is weird that the two grounds have different resistances though. 0.9 seems like a lot. They should be identical, since they're bridged inside the MAF. Try putting the multimeter in resistance mode and just touching the probes together. If the number is not zero (eg. 0.3), subtract that amount from the indicated reading when measuring resistance. This accounts for resistance in the wiring.

You can also use a long piece of wire and have a helper hold it to test the connections in the harness. So check resistance over VS from the disconnected MAF connector to the appropriate pin at the disconnected ECU connector, and it should be minimal.

If I were closer to Hamilton I'd offer to drop by and help out, but unfortunately I'm a few hours away and I'm rarely in that area.

 

For the VC I did try different placements of the ground and I selected the mounting bolt for the little sensor next to the air box on the strut tower as it had a non-coated bolt. It read 7.7.
I tried a different location and I got 3ish but I think that was what I was touching. It read 7.7~ in a majority of locations.

I did test the VC with both E2s which is a ground and I got different readings with the key off BUT I will check tomorrow with the key on and hopefully see near 5V.

I will double check the resistance amounts as I am learning as I go with this tool so thanks for pointing that out that you need to subtract it.

I think I have a spool of wire somewhere in storage. I'll go take a look.
​​​​
I don't even live in Hamilton anymore, I live further from you now as I live near London.

Also, of note, I tried to plug everything back in and she won't even start at all now. No bump or blip in the gauge cluster, no catching at all even with tapping the throttle to try and start her. She may have been flooded and I'll re-do my de-flooding trick to build compression with a pinch of oil via the spark plug holes. It just won't de-flood with either the EGI fuse removed or the gas pedal fully depressed while cranking.

​​​​​If that isn't it then maybe I killed the fuel pump trying to start it all these times recently? I found a new fuel filter that I am going to install while I remove the fuel line to check if I still have pressure... Go figure it seems everything is going wrong after being in storage. There are no signs of rodents or otherwise.

Again, I appreciate all the help, it's such a shame as she never left me stranded in the 8 years of owning her.

 

No problem, happy to help.

When you measure VC are you measuring Volts or resistance?

VC is a 5 volt supply from the ECU. The way this works (simplified) is that it's the supply voltage, and the output voltage on VS is the reading from the MAF.

Think of it like the ECU saying "I'm going to send 5V down this one line, and see what comes back on the other". If it gets 3V back on VS that corresponds to some amount of airflow.

So if you are measuring voltage and getting 7V on that line, something is up in the ECU. The ECU itself handles the voltage regulator for the 5V logic. Everything else in the car is 12V.

But I suspect what you're doing is measuring resistance and getting 7 ohms from VC to ground. Which isn't measuring whether the ECU is supplying the right amount. Instead it's measuring the resistance of the easiest path to ground through the ECU circuitry, which won't help diagnosis.

The easiest way to think about this is the old pipe analogy. The ECU is supplying 5V which is like water in a pipe. There is a small wiper inside the MAF that has variable resistance depending on how far the cone is pushed, and this resistance impedes the flow of water. By checking how much water gets through the drain the ECU can tell what the airflow was.

What we're trying to identify is whether there are any problems in the harness. If the wire for the VC pin is damaged, it might add resistance before the MAF which skews the reading. The easiest way to start diagnosing is by checking the voltage there with key to on.

When you're measuring E2 that's a bit different. It's not like VC where the ECU works on it, instead it's just a simple return to ground (like the drain in the pipe analogy). So in that case you want the multimeter in resistance mode and if it indicates a high resistance (like a blocked drain resists the water going through it) then there is a problem some place. I'd put "high" at greater than 0.2 ohms or so, but you do have to account for any resistance in the wiring. My multimeter has 0.2 ohms of resistance in its probes. So when I measure grounds on my car an indicated 0.2 ohms is actually zero.

My money is on something being weird with the ground. Those grounds (as well as the rest of the EFI system) tie together and end up at a ground lug on the intake manifold. The ground can more around as the car is serviced over the years but the exact location isn't critical. If the problem isn't a damaged wire it's also possible that this ground is corroded and the entire EFI system is unhappy as a result.

There are some additional grounds that could cause this (the engine grounds to the body through the starter ground, and there is an additional one from the engine block to the firewall). Aaroncake has a good write up on his website that I can link tomorrow.

I hope that explanation helps. I remember how much of a pain in the *** it was to learn all this stuff the first time. With cars this old the best way to diagnose is to just get a really good grasp on the fundamentals of how this stuff works.

 

It changes the tune for maple syrup

 

Ok, I understand what you are saying. I wish it wasn't pouring all week or else I would be out there. It is supposed to stop this weekend so I'll see about taking a look and report back.

 

Hey,

So I had a chance to quickly get outside and check it out. The key is in the ON position and plug is disconnected but I am getting nothing on the VC. Zip zilch nothing. I set it in this setting as you said set to DC and I made sure online this was the correct setting.

I then put the red probe in the VC plug and the black probe on a body ground (strut bolt) and nada, nothing. I checked all the wires just in case I probed the wrong one and nothing on any of them.

I noticed the battery was slightly drained but I don't think that would cause no readings at all? Maybe some voltage? I can charge the battery tonight but I thought it was weird I wasn't getting anything.

It was hailing today so I didn't have much time.

 

I heard this but to make sure I was doing it correctly I plugged it back in, unhooked the negative, and waited a minute to clear the codes according to a procedure I read about.

Still exact same codes.

 

While those probes are backward (Black should be in COM, Red in center port) that would just cause the voltage to read negative. So if you're not seeing anything on the VC wire then there definitely could be something up.

One thing to verify though is that the picture of the connector in the FSM and in the Wiring diagrams is from the perspective you're facing the MAF. Or rather, looking into the back of the connector. So when you probed VC, presumably looking into the connector, the connector is mirrored from that diagram and you might have been probing the wrong pins.

 

Sooooo.... I got out to checking it today. The car wouldn't start but I thought I'd try. I figured I'd check all the fuses and sure enough the engine fuse inside the cabin was blown. I didn't have a replacement but I took it from the fog light spot as it is the same 15a. That cured my no start and it started right up. This time it lasted 20-30 seconds and idled before it died again.

I started her up again and the old issue of starting, hitting 3000 rpm and then dying even with pedal depressed still happened.

I checked the plug again with a proper battery charge and I am getting consistent readings. I have attached a picture to make sure I am probing the correct ones.

So from right to left with key to the ON position:

​​​​​4.97v
0.00
0.00
​​​​​​4.97v
1.5v but then drops to 0 or near 0 when I hold the probe on.



Now, I don't know if this is supposed to happen or what BUT I tried to run it without the MAF plugged in and I could keep her running, she wouldn't idle though, and after about a minute I heard the 15a fuse blow and the engine shut off. I was trying to see if I could keep her running and plug the MAF in to see if it would die but the fuse popped first. I'm guessing this must have happened when I was trying the move it the first day as I was trying to move it without the MAF connected and then it just wouldn't start after so...I would also like to mention that it doesn't pop right away, so it's not a short I'm guessing. And it doesn't pop when the MAF is plugged in... Only when the MAF is unplugged and I try to keep the car running.

Related or unrelated?
Thanks again!

edit: the tach wasn't working the first two starts and shut offs, it worked again when I unplugged the MAF but that may be coincidental as before these issues the tach would sometimes not work and randomly kick on while driving. It was rare but happened.

 

I think something is still reversed. Left to right (looking into the connector as you've photographed it, not into the back of the connector as the manual shows it) that would mean the following:

VS - Sensor reading voltage - 4.97V
VC - Sensor supply voltage - 0V
E2 - Ground - 0V
E2 - Ground - 4.97V
THA - Thermistor reading - 1.5V

Somehow that would imply that the E2s are not connected (they can't have different readings, they're one circuit internally), and that the ECU is supplying 0V to the sensor and receiving 5V back. If we reverse that though (take your readings and apply them to the way the manual shows the connector, looking into the back of it) we get something that makes more sense:

VS - Sensor reading voltage - 1.5V
VC - Sensor supply voltage - 4.97V
E2 - Ground - 0V
E2 - Ground - 0V
THA - Thermistor reading - 4.97V

It's a bit weird that there is voltage floating around on the THA and VS pins, but then maybe the thermistor has a pull-up resistor inside the ECU or something. And the VS voltage might just be whatever floats around on that pin when the MAF isn't there. I don't really know without popping the ECU open. I don't think either of those is a definite culprit since it seems like you have a short based on your other symptoms.

A short could still cause a slow burn. Fuses burn from heat, so if it's a small short (maybe the sheath on two wires has eroded and caused a bit of contact) and there are 16A on a 15A circuit it could take a couple of minutes for the wire to get hot enough. Most cheap fuses also have surprisingly poor tolerance (never buy the Amazon ones).

I think this sounds a lot like there's a short somewhere in the harness. I don't know why the MAF being plugged in would prevent the short from burning the fuse. I know you earlier measured 7.7 ohm resistance between VC and a random ground. The trouble is that this could be through one of the ECU circuits or something and might be normal. I don't have a stock ECU around (well I do, but I have no idea where) or I'd offer to measure for you. What you could do if you feel comfortable with it is unplug the ECU under the carpet and try measuring again at the MAF connector between E2 and VC. If there's any continuity, that would mean a break in the harness somewhere is allowing contact.

The tachometer is driven from the trailing coils. I haven't really dug into how they're wired but if it's happened before I'd ignore it. The car will run on just leading. You can always verify with a spark checker next time it happens.

 

Actually, I found my stock ECU and measured between a ground pin and the VREF pin, and got zero continuity. That's not a guarantee (it's an S4 ECU and I haven't used it in a couple of years) but it lends credence to the idea that there might be a short on those wires.

 

Ok am I losing my mind here? I went back to go check in the dark, to make sure I got the right pins and readings.

Left to right while looking at the plug face on (starting with the discoloured pin)

Black wire 5v but then drops down to near zero over time
White/red (I think) 4.97v steady
Red/black 0
Red/black 0
Green/??? 4.97v steady

Am I losing my mind or wouldn't the two matching wires be both grounds?

Again, I know this must be annoying having to explain everything to me but I really want to drive her this summer again.

Thanks!

Edit: So she will start up until she floods BUT I got her started 5 times and no blown fuse, the one time I started her I almost kept her running but it felt like the intake wasn't connected. Almost as if my gas pedal was not allowing more air in. It keep going down but my foot was on the gas pedal and it would almost be as if it would catch it quickly before it died then go up and then back down and die. i don't know how to explain it properly...

 

Your most recent readings make sense. Here's a diagram I made to make this easier:



The top image from the manual is looking into the connector on the MAF, so we want to look at the bottom diagram which is reversed (looking into the connector on the harness). Just putting it here for easy reference.

The middle three make complete sense. The 5V on the white/red would be the reference voltage from the ECU, and the other two are grounds so they have 0V on them.

The first and last I don't know what to make of unfortunately. It might be that this is normal (what you're basically measuring are voltages on some ECU pins, so this might be a normal reading when there's no MAF connected) or it might be that there's a small short somewhere. I don't know which. I think the next steps would be to pull back the carpet and start checking for shorts with the ECU unplugged, or check each ECU pin against the manual one by one and identify any that are out of spec. I wish I had more advice for you but I don't know enough about the internals of the ECU to say if that's a normal reading or not, and no longer have the stock ECU in my car at all.