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Author Topic: Up & down idle 88 Duke when warm  (Read 33429 times)

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Donster

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Re: Up & down idle 88 Duke when warm
« Reply #105 on: February 11, 2019, 03:43:40 am »
OK, just to be on the safe side, I've ordered another IAC and another MAT sensor, just in case mine were no good (but NO error codes??).
Should be here next Monday.

If I still can't get rid of the issue, I'm willing to replace the ECM (minus the PROM of course).

So, just in case, does anyone have a spare 88 Auto-Duke ECM?

\D
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Donster

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Re: Up & down idle 88 Duke when warm
« Reply #106 on: February 15, 2019, 12:24:30 pm »
Ready for this?

New IAC - RUNS STEADY! ;D ;D ;D

Must have had a bad IAC out of the box.  :(
Thanks all!
\D
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Raydar

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Re: Up & down idle 88 Duke when warm
« Reply #107 on: February 15, 2019, 02:27:40 pm »
Quote from: Donster on February 15, 2019, 12:24:30 pm
Ready for this?

New IAC - RUNS STEADY! ;D ;D ;D
....

I'm happy to hear it! This was turning into a real head-scratcher.
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Donster

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Re: Up & down idle 88 Duke when warm
« Reply #108 on: February 15, 2019, 02:39:59 pm »
If that ain't the truth!
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GTRS Fiero

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Re: Up & down idle 88 Duke when warm
« Reply #109 on: February 15, 2019, 03:46:17 pm »
Awesome news!
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Donster

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Re: Up & down idle 88 Duke when warm
« Reply #110 on: February 25, 2019, 11:32:14 am »
Well, I guess I spoke too soon, but it was good while it lasted.
We ran her real hot yesterday and the symptoms returned..up and down idle, to the point where the engine stalls when in R or D.
So, after reading the newest club news letter, I figured I have a few MAP sensors, so I tried them ALL out. They are all 1 BAR GM MAP sensors, one of them supposedly new. Same issue with all of them. But here is the peculiar thing........when I disconnect the MAP (although I get a CES light), the engine runs great at about 1K RPMs. I put it in gear (D or R) and it drops to around 900 RPMs, but stable.
What the hell, over??

Any ideas?

\D
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Fierofool

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Re: Up & down idle 88 Duke when warm
« Reply #111 on: February 25, 2019, 05:45:28 pm »
Maybe German Fieros didn't have MAP sensors.  Leave it disconnected.  You know they're always ahead of us, automotively.   :P
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GTRS Fiero

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Re: Up & down idle 88 Duke when warm
« Reply #112 on: February 25, 2019, 06:00:30 pm »
As you read my replies, keep in mind that I know nothing about the 4-cylinder Fieros; I am correlating from the V6.

The DIS ECU seems to handle a lack of MAP sensor input differently.  The MAP sensor is for fueling, which means you have a fueling issue.  Did you check for vacuum on the MAP sensor vacuum line?

Did you run the voltage tests in the newsletter?  Since it is the same MAP sensor, the voltage tests should be the same.

The TPS, O2, and MAP sensors work together to help the ECU control fueling.

Oh.  You'll probably need a scan tool to reset the code on your ECU.
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Donster

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Re: Up & down idle 88 Duke when warm
« Reply #113 on: February 26, 2019, 07:53:29 am »
All voltages check out (as far as I can tell).
Vacuum checks out also.
Can't scan the 87-88 L4.
Have a new (refurbished) ECM on the way.
But I also read in Ogre's cave, that the fuel vapor canister can cause problems, so I'll be inspecting it tonight for cracks or other irregularities.

\D
« Last Edit: February 26, 2019, 07:57:41 am by Donster »
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GTRS Fiero

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Re: Up & down idle 88 Duke when warm
« Reply #114 on: February 26, 2019, 08:02:19 am »
Well, if the fuel tank has been overfilled, yes, the canister is going to be an issue.
« Last Edit: February 26, 2019, 06:17:30 pm by GTRS Fiero »
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Fierofool

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Re: Up & down idle 88 Duke when warm
« Reply #115 on: February 26, 2019, 08:47:51 am »
Can't you insert a jumper in the A & B terminals of the ALDL and read the codes?  To clear the codes, disconnect the ECM power supply at the battery, just like you would on a V6. 
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TopNotch

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Re: Up & down idle 88 Duke when warm
« Reply #116 on: February 26, 2019, 11:14:53 am »
Quote from: Fierofool on February 26, 2019, 08:47:51 am
Can't you insert a jumper in the A & B terminals of the ALDL and read the codes?  To clear the codes, disconnect the ECM power supply at the battery, just like you would on a V6.
Jumpering A-B does work on an 88 duke. Been there, done that.
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Donster

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Re: Up & down idle 88 Duke when warm
« Reply #117 on: February 26, 2019, 12:19:56 pm »
Yes, shorting A&B to read error codes works fine, you just can't hook up a scanner tool, like WinALDL. That is what I meant with:
Quote from: Donster on February 26, 2019, 07:53:29 am
Can't scan the 87-88 L4.
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Donster

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Re: Up & down idle 88 Duke when warm
« Reply #118 on: February 26, 2019, 12:21:37 pm »
BTW: Checked fuel vapor canister, nothing to be found.
Now I really am hoping that it is the ECM.
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GTRS Fiero

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Re: Up & down idle 88 Duke when warm
« Reply #119 on: February 26, 2019, 06:15:34 pm »
Quote from: TopNotch on February 26, 2019, 11:14:53 am
Quote from: Fierofool on February 26, 2019, 08:47:51 am
Can't you insert a jumper in the A & B terminals of the ALDL and read the codes?  To clear the codes, disconnect the ECM power supply at the battery, just like you would on a V6.
Jumpering A-B does work on an 88 duke. Been there, done that.

Were you able to scan your ECU?  I know scanners exist.  I think my brother has one.
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