symptons of a bad AFM?

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Postby Gary » Thu Sep 14, 2006 11:44 am

I see. You are using troubleshooting with "voltmeter"
Basically you pull the connectors out of the ECU and measure the voltage on the connector side, not on the ECU side.
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Postby mison » Thu Sep 14, 2006 12:36 pm

I know, but some measurements is with runing engine... how can engine idling with upluged connector?
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Postby Sleeka_89 » Thu Sep 14, 2006 1:39 pm

my guess would be to leave it connected and probe into the wire using a voltmeter if you need to check with it running :shrug:
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Postby Gary » Thu Sep 14, 2006 11:43 pm

Sleeka_89 wrote:my guess would be to leave it connected and probe into the wire using a voltmeter if you need to check with it running :shrug:

That makes sense.
If you are measureing the resistance of a sensor, it should be disconnected from the power source (ECU)
If you are measuring the voltage, (at idling or while cranking), it should be connected to the power source (ECU).
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Postby mison » Fri Sep 15, 2006 9:02 am

it is not writen correct I think. "perform all voltage measurements with the connectors disconnected" and then I must measure Volts at idling or 300rpm or crank. It is not possible, because ich I will unplug any connector from ECU, engine cannot run.? Maybe your book is right..all connectors connected. I cant write in in eglish right, because I don´t know english, but I am a electrician and this is obscure for me :) I think it must be cennected and measured with thin probe?Does anbody here measure voltage on ECU?
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Re: symptons of a bad AFM?

Postby Awesome-Trac » Fri Aug 19, 2011 1:46 am

this is a old post but i might be able to help regarding pluged or unpluged connectors, have two jumper wires bridge between both connectors, then use meter to measure while car is running....my explaination is kind of garbage but its what a instructor for Toyota told me to do
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Re: symptons of a bad AFM?

Postby 1990ST185 » Thu Apr 16, 2015 3:22 am

I would like to know as well.
A year ago I thought I had a fuel pump problem so I replaced it with a Bosch Fuel Pump 0 580 254 979. It wasn't that it ended up being the Air Bag Sensor so I disconnected it and it drove nice.
It was becoming into a nice daily driver till I started to feel the car to bog down and felt like it was misfiring.
I changed out the spark plugs (NGK copper)
BOSCH distributor cap & rotor with BOSCH wire set.
When I was removing the old plugs I saw that 2 & 3 was full of oil. I assumed that the valve cover gasket was old and having a leak by so I also replaced the valve cover gasket.
Put everything back and the car felt like it idles very rough and dies after maybe 10 seconds unless I kept the foot on the gas. I was thinking it might be the throttle body with carbon buildup so I cleaned it well.
I also cleaned the EGR valve.
I put everything back and NADA car idles a little better but still rough idle and then dies a few seconds later.
I then moved on to the AFM I tried it connected and it dies.
Later I disconnected it and BAM the car stays on.
After running it for a few minutes I gas it a bit but it dies.
Have I narrowed it down to the AFM or is there another gremlin waiting after the cleaning of the AFM???
PLEASE HELP TOYOTA ST185 GURUS :notworthy: :notworthy:
Thank you for your time
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Re: symptons of a bad AFM?

Postby 2RM » Thu Apr 16, 2015 10:55 am

not a guru! :D but what is your vacuum reading? sounds a lot like a vacuum leak to me...
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Re: symptons of a bad AFM?

Postby 1990ST185 » Thu Apr 16, 2015 12:30 pm

2RM wrote:not a guru! :D but what is your vacuum reading? sounds a lot like a vacuum leak to me...


I'm not quite understanding 2RM. What do you mean by vacuum reading? Where can I see these vacuum readings from the car? I did end up cleaning the AFM last night with MAF and contact cleaner... :?
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Re: symptons of a bad AFM?

Postby 2RM » Thu Apr 16, 2015 2:30 pm

do you have an aftermarket boost/vacuum gage? Vacuum reading should be 19-21 in.hg. Check that.
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Re: symptons of a bad AFM?

Postby 1990ST185 » Thu Apr 16, 2015 9:56 pm

2RM wrote:do you have an aftermarket boost/vacuum gage? Vacuum reading should be 19-21 in.hg. Check that.


No sir I do not have a boost or vacuum guage. I'll get one from Harbor Freight and see what happens. What line do you suggest to hook up a vacuum guage to.

Just curious but can a fuel injector cause a problem like this?
I will try to post up a link for a video on how the alltrac runs with and without the AFM hooked up.
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Re: symptons of a bad AFM?

Postby 2RM » Fri Apr 17, 2015 4:40 pm

there is an outlet on the back of intake manifold that is not used, its plugged. If I remember right its on the left side. Hook up to that. Its prolly the best place to hook up. Look at your vacuum hoses make sure all of them hooked up, if they are dry rotted and cracked up replace them. Usually with AFM not hooked up your car will start for 2 sec. and shut off, check engine light should come on also. Post up vids, it will help.
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Re: symptons of a bad AFM?

Postby CTechBlueDragon » Sun Apr 19, 2015 11:35 am

The most sure symptom of a bad AFM is if you still find one in your engine bay. :shrug:
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Re: symptons of a bad AFM?

Postby 1990ST185 » Mon Apr 20, 2015 11:55 pm

2RM wrote:there is an outlet on the back of intake manifold that is not used, its plugged. If I remember right its on the left side. Hook up to that. Its prolly the best place to hook up. Look at your vacuum hoses make sure all of them hooked up, if they are dry rotted and cracked up replace them. Usually with AFM not hooked up your car will start for 2 sec. and shut off, check engine light should come on also. Post up vids, it will help.


Here is the link of video...

https://youtu.be/EOGn-HSb06w

Hope this helps
:( :cry:
Thank you
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Re: symptons of a bad AFM?

Postby 2RM » Tue Apr 21, 2015 12:58 pm

ok, did you try to connect your AFM, reset ECU by neg battery cable disconnect or pull EFI fuse in fuse box, with all hooked up start the car? Did you get check engine light? Did you read the codes? And that lil filter on your breather... that is supposed to be routed back into intake. Hook it up the way it should be, cause it could very well be your problem. So your vac reading is around 12 inhg??? Is that right? If so that's way too low at idle. Get rid of that breather filter, rout that line back in to intake the way it should be. And I think your problem is not AFM IMO. Start replacing all those vac line hoses, its a good thing to do to eliminate problems down the road anyway.
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