You finally explain what that means. So im testing afm fc and isc tomorrow

Look at the wiring diagram and it may be obvious. ;) Test the Vs signal as I've detailed too. Don't go discounting anything because you don't think they fit the bill.... Your gut feeling has yet to provide any reason for me to have faith in it.

ill try to test it today but i have limited time. the main this that seems to be is this crazy volt drop. i still suspect the ecu because before mentioned, jump a car later that day my temp gauge stopped working. got a new sensor did the same thing. notice that my oil pressure gauge jolts a bit but its not plugged in. both of those things are from the computer. alternator is also controlled by the computer. along with all the information that is sent to it and its outputs. when that car shuts off there is no affect to my radio what so ever. and as its dying to the best of my knowledge my lights arent dimming. so its has to be something in the ecu or its wiring because when the car is off im not getting heart stopping voltage drops. i know everyone says that ecu is a last resort but this is not normal.(btw you never get answer my question about the ecu, which one can i put in my car) but im going to test those things like you said after running the car

and as of this morning cygnus is down

Unless I'm completely wrong, the alternator is not controlled by the ecu. It has an internal voltage regulator in the alternator. Also, the voltage you reported at idle is too low, it should still be 13.5 volts. As engine speed changes the available current will change as well, however the voltage should remain constant if the wiring and alternator are both working properly.

Tested the afm and bench tested all it spec along with the isc. Couldnt do fc because I ran out of time. But I found a lead. Ignition switch black and yellow wire. Its apart of the alternator ecu

Alt is brand new and ecu is connected thru battery. From bat to fl am2 to efi fuse then it splices off before main relay as a black and yellow wire

Omfg. Checking my ecu connectors and heard a click. Turn on all electrical loads when I got home and car didnt die...

Should be and commonly is are two different things. Most of the MKIII's I've worked on (except mine after rebuilding harnesses) have a significant drop when loaded heavily... I'm not saying it's proper or optimal. That's beside the point though, the point was that the ECU won't fail until the voltage drop a LOT further then the spec 13.2v to 15v.

No idea who said anything about the ECU being controlled by the ECU.

well based on the next couple of days will verify if that was the real problem. and if it was that I WAS RIGHT HAHAAH ECU RELATED lol

AH HA wiring to the isc connector looks jacked up and my isc sometimes doesnt click like its suppose to. So today imma fix that TONIGHT!!!

Btw what the f is a fuel pressure up vsv and its purpose and location. I found bits and pieces but cant find a solid article

There was a VERY detailed write-up on it on here a couple years back. I'll try to see what I can find later on. I don't have time right now.

It's used to modulate vacuum reference at varying loads. It's a good thing, all around. Do you have a specific questions about it or just curious? Yes, you do need it.

Well if you remember when I first got this car and joined this web site
I posted pics of 2 connectors I didn't no. one was the knock sensor and the other was never figured out. Based on the color of the wires and placement of the vsv on diagrams, that connector goes to that vsv. I don't know exactly how it works yet but the ecu hadn't had a reading from it since I owned it

I'm sorry, I don't remember... For a low traffic site there's enough to push it all out of my mind after a couple days.

The ECU doesn't "read" anything from the VSV. It doesn't even check load to ensure it's in place. There will be no code in its absence or if it's defective. If it isn't present it needs to be replaced. It isn't a common failure point but it is something which should be tested periodically as well... Fueling is the one thing that can destroy an engine in seconds.

Search the MKIII section for vacuum diagrams to see how it's supposed to be plumbed into the system. There are three nipples, one goes to the FPR, one to the manifold for vacuum and the third just has a small filter on it. You may find the vacuum diagrams in the FAQ section (if you find the vacuum line thread and it's not in the FAQ section let me know and I'll move it there).

When I check that writing tomorrow ill try to see if every thing is plugged up where it should but as for the connector it done. It broke off about a month back so I'm lost there

checked resistance of the isc again and it is still in spec.

check the wiring from fuse box to isc connector and the connect to the ecu connectors and all showed .5 ohms

cleaned the isc again with seafoam running though its airport this time. last time i removed it and cleaned it

some days i hear the isc clicking after shut off and other days i dont ( might try a different one if i can find one that is not 366 bucks

i found it weird that i held the vacuum line to the isc closed and the port on the throttle body closed and it continued to run

i also started the car with the isc connector unplugged and it just kept revving up

so im going to move to fuel and see if i can find something strange

i didnt get a chance to fully check the fuel pressure up vsv because that engine bay got a little too hot for me so im going to study up.

so i hope the info i provided can give you some clues because i am running out of options

i really want to bypass this fuel pump resistor and see what happens because resistance for the fuel pump just sounds dumb. but i would like ur 2 cents to see if it is a good idea

Nothing wrong with that at all I recommend it depending on the issue. I don't think it's the problem here though, but go ahead and try. I recommend you bypass at the bigger round connector as that will bypass both resistor and relay. Use an appropriately large gauge wire and a couple spade connectors to make a reliable and easy to remove bypass wire. Refer to the TEWD to see which two contacts you want to jumper.

for the relay should i use a switch if i am going to bypass it because i dont want it on all the time

No, just unplug the harness connector and plug in the wire jumper with uninsulated spade connectors on the end. When you're done testing unplug the jumper and plug the factory harness right back in. You cut nothing, solder nothing, permanently modify nothing. Use 10GA or 12GA wire for the jumper. This is a diagnostic tool, not something you install to leave in the car.

i was thinking more perm and driving my car to work as a test run LOL

You can drive it. You'll run excessively rich at idle and low to low-mid loads.... might make your problems worse. The whole point of a good heavy gauge wire and crimped on spade connectors is so you get the most solid connection and the wiring will handle the load without over heating... And it's easily removed. The reason for bypassing at the big connector is because the relay is the common fail point of the two... the resistor pack's are pretty bullet proof.

Well the resistor pack is out of spec but wouldn't that pressure reg keep it the same resistor pack or not. And where can I get a new pack because I can only find used ones

No, the fpr doesn't guarantee pressure and volume. The FPR can only flow so much. At higher loads the injectors run at a much higher duty cycle and effectively bleed off a good amount of pressure. I could imagine the increase in pressure from the pump killing an old FPR.

What you're calling "out of spec" is nothing. A cheap meter alone may report that far off. What temp was the resistor pack when you measured it?

I think you're starting grasping at straws and need to go back over what's been covered, see if there's anything you've neglected to check that's been listed.

You expect me to have thermometer? It was hot as hell if thats what you mean. I've replaced the entire ignition system and tested every sensor at least twice. I also replaced the entire charging system. I'm exhausted all my money and haven't gotten any closer to solving anything

Too much to ask, eh? And no, I wasn't looking for an exact measurement. Resistance through any conductor increases in proportion to temperature... heat it up and there's more resistance.

Don't blame me, I didn't recommend you spend a single cent on the charging system (I may have suggested spending $5 on new brushes for the alternator) and warned you to stop just throwing cash at it.


When you're done huffing and puffing: Clean ALL of your grounds (big and small, on the engine block, the intake manifold, driver's side kick panel and ECU) and battery cables. Test the AFM's Vs signal voltage at the ECU with someone moving the vane (I linked to a more detailed description on how to do this a long way back in this thread. Do it both when the AFM is cool and the heat it up heavily with a hair dryer and test again), test FC on the AFM both when it's hot and when it's cool. Wiggling wires does dick... take measurements, test for voltage drop. Check for loose, broken, corroded connectors. Test for voltage drop across Vc from the ECU to the AFM and TPS connectors. Vc should measure around .48 to .5v. Go through the fuse boxes and replace any fuses which are not the proper value (and make sure the previous owner didn't bypass anything else like they did with the 100A FL). Bypass the fuel pump resistor pack and relay if you like, it's not going to hurt anything to try it but generally it fails the other way around. You got rid of the code 51 right? Verified that the vacuum lines are all run properly? ALL of this should take 2 to 3 hours... for a complete novice it shouldn't take more than 3 days.

I replaced the charging system because I had the wrong battery in and th old alt output was terrible now where is this ground on the manifold because alot of things says its there but ive yet to find it. I have cleaned and checked all the engine bay grounds and they are fine. Im going to end up making a video and showing you whats happening

It's SUPPOSED to be bolted to the flange where the lower and upper halves of the intake manifold meet. Cylinder #5 to be precise.

Don't bother, I'm out.

I re-read the entire thread. I missed the item about plugging the ISCV's supply with the throttle closed and the engine still running. This strikes me as a bit odd. If the throttle plate isn't closing completely it needs to be corrected.

^^^Have you made it through this yet?

You should also have a look at the wiring to the climate control head unit, the blower and inspect the blower motor resistor pack for damage or tampering.

Did you replace the fusible link?

Have you located the grounds to the intake manifold?

Does the car die if just the heater is turned on or just if the blower is on at all?

Did the fuel pump resistor bypass get you anywhere?