09-19-2006, 08:04 AM
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Senior Member
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Join Date: Jul 2003
Location: Salem, NH
Posts: 897
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Air temp sensor in AFM
I have been trying to debug an annoying hard start problem for awhile now and finally was able to put my AutoForce tester to some good use...If I let the Verde sit for a few days without using it or sometimes if I just start it up to move it and then let it sit it will be very hard to start. In one of the latest episodes I connected up the AutoForce and was able to start the car by using the setting to fake out the ECU into thinking that the air temp sensor was putting out 300 ohms. The problem is I can find very little documentation on the air temp sensor anywhere in any L-Jet documentation.
I find mentions of it and that the inputs from it are used to richen or lean the mixture depending on the temp of the air coming in but I cannot find any specs on what the ohm outputs mean.
The weird thing is if I don't let the car sit for a few days it will start up without these problems.
Thanks,
Kevin
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86 Spider Veloce
87 Verde
Milano registry custodian( www.alfamilano.com)
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09-19-2006, 12:30 PM
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75/Milano manuals for all
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Join Date: Apr 2004
Location: Melbourne Australia
Posts: 1,630
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G'Day Kevin,
10°C (50°F) 7 - 12 k ohms
20°C (68°F) 2 - 3 k ohms
80°C (176°F)  250 - 400 ohms
Note: This is the same as the coolant temp sensor.
Ref: My site, Electrical & Electronic Diagnosis, Section "D" page 25. |
09-19-2006, 12:43 PM
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Join Date: Nov 2002
Location: San Jose, CA
Posts: 1,962
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Craig, do you have the resistance numbers for the 164 / Motronic cars? Do they have the same air temp sensors as the older L-Jet cars?
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09-19-2006, 01:28 PM
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75/Milano manuals for all
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Join Date: Apr 2004
Location: Melbourne Australia
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G'Day Nizam,
Motronic: see pic
Note: This is the same as the coolant temp sensor.
Ref: My site, Electrical & Electronic Diagnosis, Section "C" page 3.
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09-19-2006, 02:20 PM
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Location: San Jose, CA
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Thank you, Craig! I was thinking about transplanting an L-Jet Air temp sensor into a known-faulty Motronic AFM. Complications of the transplant aside, it would appear that the values are similar.
Agree?
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09-19-2006, 03:07 PM
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75/Milano manuals for all
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Join Date: Apr 2004
Location: Melbourne Australia
Posts: 1,630
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Except at the low end.
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09-19-2006, 05:06 PM
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Senior Member
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Join Date: Jul 2003
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Thanks Craig!
Kevin
__________________
86 Spider Veloce
87 Verde
Milano registry custodian( www.alfamilano.com)
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09-27-2006, 09:44 PM
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Registered User
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Join Date: Oct 2003
Location: sunny singapore
Posts: 77
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 Quote:
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Originally Posted by Craig
G'Day Nizam,
Motronic: see pic
Note: This is the same as the coolant temp sensor.
Ref: My site, Electrical & Electronic Diagnosis, Section "C" page 3.
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hi craig,
do you know if anyone sucessfully converted the motronic AFM to MAF? http://www.elecauto.com/desarrollo.htm
i tried it few months back but ran into some problems, installed a 2.0TS 16v MAF from the alfa 156 and ran it with Unichip.
it started fine and ran well, but i have a problem with the engine runs hot. i would be cruising and when coming to a stop, i engage neutral to let it cruise the rpm would drop and engine would stall, i can restart immediately (on the fly) without problem.
but this doesn't happen when i am idling and rev the engine, the rev will drop and hunt for a couple of sec and idle steadily.
want to confirm if i got the pinout of the AFM correct?
pin 1: CO potentiometer
pin 2: AFM signal
pin 3: supply +5v
pin 4: earth
pin 5: air temp sensor +
i have the alfa 156 MAF pinout as these:
pin 1: temp sensor +5v
pin 2: supply +12v
pin 3: ground
pin 4: supply +5v
pin 5: air mass signal output 1-5v range
i was thinking maybe i need to transplant the CO potentiometer from the AFM to the MAF and plug the wire in, maybe same for the air temp sensor?
i have since revert back to the AFM as i have just rebuilt my engine so would want to make sure everything runs fine before i starting messing around with it again. at the moment the spliced set of 5 wires is still dangling in the engine bay ....
anyone got any clue or suggestion?
__________________
'89 Alfa 75 2.0TS
ex '91 Alfa 33 Sportwagon 1.7i 16v
ex '96 Alfa 146TI
ex '97 Alfa 146 1.6TS 16v
ex '99 Alfa 156 2.0TS 16v Selespeed
ex '89 Alfa 33 1.5TI
[IMG]http://www.hotwheels.com.sg/products/picture%20gallery/evo%20kit%20front%20side.JPG[/IMG]
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09-28-2006, 04:05 AM
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75/Milano manuals for all
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Join Date: Apr 2004
Location: Melbourne Australia
Posts: 1,630
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G'Day ????,
Quote:
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Originally Posted by sslim
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Quote:
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Originally Posted by sslim
i tried it few months back but ran into some problems, installed a 2.0TS 16v MAF from the alfa 156 and ran it with Unichip.
it started fine and ran well, but i have a problem with the engine runs hot. i would be cruising and when coming to a stop, i engage neutral to let it cruise the rpm would drop and engine would stall, i can restart immediately (on the fly) without problem.
but this doesn't happen when i am idling and rev the engine, the rev will drop and hunt for a couple of sec and idle steadily.
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I don't know enough about unichip.
Quote:
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Originally Posted by sslim
want to confirm if i got the pinout of the AFM correct?
pin 1: CO potentiometer
pin 2: AFM signal
pin 3: supply +5v
pin 4: earth
pin 5: air temp sensor +
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Yes, this is correct but pin 3 is specified as AF ref. voltage.
Quote:
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Originally Posted by sslim
i have the alfa 156 MAF pinout as these:
pin 1: temp sensor +5v
pin 2: supply +12v
pin 3: ground
pin 4: supply +5v
pin 5: air mass signal output 1-5v range
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This seems correct for some 156 MAF's but I don't know much about 156's.
Quote:
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Originally Posted by sslim
i was thinking maybe i need to transplant the CO potentiometer from the AFM to the MAF and plug the wire in, maybe same for the air temp sensor?
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The ECU would need to see a temp sensor but I would have expected the unichip to supply this. The CO pot is less critical and would normally provide about 2.5V to the ECU.
I think this post proves I don't know everything 
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