Dies when unplugging AFM

[Devin LeBlanc]

So, I know it really doesn't matter, But my two other friends with mk3's you can start the car with the AFM unplugged, or with it idling unplug it and it stays running, you can even rev it a bit... But for some reason when I unplug the AFM mine dies right away.. and wont start with it unplugged.. What could cause this? hmm

Thanks:nono:

 

[jetjock]

It'll matter when the AFM fails and you end up stranded, which is not what Toyota intended when they designed the car.

 

[dubsupra209]

maybe its the afm you have...

 

[jetjock]

^ Seems to me having it unplugged kind of puts a crimp in that theory...

 

[mkIIIman089]

maybe its the afm you have...

Might be that burned out tail light too.

 

[Devin LeBlanc]

So what could cause it then?

 

[jetjock]

Are your friend's cars stock?

Could be lots of things but without knowing what you've done to the car it's tough to even guess. All I can say is:

1) The AFM isn't used for starting the engine even when it is connected. That alone proves you have a problem.

2) If everything is working right the engine should rev to appx 3000 without it. Can be driven like that all day long.

3) Assuming everything else is working AFM fail safe is primarily dependent on the STA and TPS signals. Since you didn't mention having codes your problem could be anything from tuning to poorly done modifications.

Keep in mind all this applies only to a GTE. A GE can run with a bad AFM but for sure won't run with the connector removed.

 

[Devin LeBlanc]

Well its a GTE technically, just a GE block and head, But Im running everything from a GTE from the fuel pump, to the injectors, manifold, same year wiring harness and ECU, With correction off in the SAFC it does the same. I know I have a problem, now I just have to find it. The diagnosing begins! This is my favorite part about working on cars, Its a challenge that it fun that always turns out to be something stupid half of the time haha.

I will start double checking everything, I do not have any codes present other than 34 from hitting fuel cut, But if I clear it it reacts the same, I will take a video and post it.

 

[Devin LeBlanc]

Heres a video guys!
http://www.youtube.com/watch?v=VRuUID0x18s

 

[bioskyline]

well dont unplug it then problem solved lol

the only thing left of the original ge is block and head right? being higher compression than the gte block the ecu might not be able to guess the correct a/f ratio?

 

[Devin LeBlanc]

Compression does not play a role in Air fuel ratio, and as far as that goes they are perfect, VF is 2.5 volts while cruising..

" well don't unplug it then problem solved lol"

Problem not solved, becuase the car should still run a drive without a AFM plugged in or even on the car for that matter to a certain extent. Also the ECU does not "guess" the correct A/F ratio..

 

[bioskyline]

hmmmmm my 87 runs with it unplugged, but it wont boost, once its hits 0 on the boost gauge it rpm locks and rumbles, missfires and generally runs like crap.

in the video i dont see the stock pressure sensor, is it installed and im just not seeing it? im wondering if the ecu doesnt try to run on speed density with it, even thogh the tsrm shows it as only running the gauge. could be an idea?

 

[Nick M]

Also the ECU does not "guess" the correct A/F ratio..

Calculations are not guesses, this is correct.

 

[jetjock]

Uh, you claimed it wouldn't start...

 

[toyolla86]

im not vastly familiar with the 7m but on the 4a the afm has a relay that turns on the fuel pump. so if the afm was unplugged car dies. and it wont start either. which afm and or ecu do you have.


sorry i didnt read page 2.

 

[TurboStreetCar]

i dont see the stock pressure sensor, is it installed and im just not seeing it? im wondering if the ecu doesnt try to run on speed density with it, even thogh the tsrm shows it as only running the gauge. could be an idea?

TCCS cannot see the boost sensor. Its only wired into the dash wiring.

What is the problem with the car other then it doesnt run with it unplugged? What made you unplug it and see if it runs?

 

[Devin LeBlanc]

The car runs fine, no codes ect. But the funny thing is, When I first got it running I started it without the AFM and let it idle and it ran fine.. But now it does not. My two other friends cars run with it unplugged..

 

[3p141592654]

I have seen this before. Sometimes it takes a few start cycles before the MIL light comes on with the AFM unplugged. Then it will run as JJ says. If it is unplugged and the MIL light is off, it won't stay running, but should crank and fire briefly.

 

[Dirgle]

It's late so I might not be thinking straight, but what if the signal for VC was severed on the ECU side. The signal would be shunted through the AFM and throw the TPS completely off if the AFM were unplugged. This could be tested with a multimeter by checking for continuity between pin 3 on the 24pin ECU connector and pin 1 of the TPS connector.

 

[Compton74]

are you running the gte or the ge afm?