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1984 Fiero SE 2M4 Dies After Letting Off Throttle by Sanhino
Started on: 03-22-2020 12:41 PM
Replies: 2 (50 views)
Last post by: theogre on 03-23-2020 05:19 PM
Sanhino
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Report this Post03-22-2020 12:41 PM Click Here to See the Profile for SanhinoSend a Private Message to SanhinoEdit/Delete MessageReply w/QuoteDirect Link to This Post
The title pretty much explains it. I've been having high idling issues which is in another thread, but when it feels like cooperating and idling properly, when I give it gas and let off it drops down to about 400-500 rpm and sometimes is able to pull itself out of it, and sometimes just flat out dies. My first thought is the fuel pump but I previously spliced in a fuel pressure gauge and fuel pressure isn't dropping when this happens, it consistently reads about 10-11 psi consistently. I've also replaced the IAC, TPS, and MAP sensors, as well as the vacuum lines as part of my high idling issue. Any thoughts?

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Gall757
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Report this Post03-22-2020 08:27 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
The two issues may be connected. There will be a bit of re-learn time for the computer after working on the high idle problem.
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theogre
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Report this Post03-23-2020 05:19 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:
The two issues may be connected. There will be a bit of re-learn time for the computer after working on the high idle problem.
While first part is likely very true... Second isn't if you drive the car.

These old ECMs are very dumb and forgets most things every time keys is off. For that matter Forgets most things in a few seconds to a minute or two when the engine is on and running. ECM needs standby power mainly to save DTC(s) set by whatever errors cause by iffy/bad sensors etc.
Is why ECM needs driving > 35mph to reset IAC every time you run the engine.

NORMALLY IAC will be close to same setting to get cold engine to work right but ECM has nothing to make sure IAC is true until that reset cycle.
New IAC or just take out old IAC to clean the port then ECM is more confused until the reset cycle.

You need a ECM scan tool to read sensors etc. because iffy wiring and plugs may make sensor value read way wrong, ECM sees low/high volts regardless of volts You see elsewhere, and more.

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