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95 Dak 3.9l clean but low idle 500rpm

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Old 06-03-2018, 10:50 AM
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Default 95 Dak 3.9l clean but low idle 500rpm

I fixed all my vacuum issues, replaced egr, changed the TSS, cleaned the throttle body, replaced IAC, I've got a new fuel pump, and I have a new rotor and distributor set. I had a NAPA mechanic tell me that the RPM is computer controlled on this model. He said if its running clean I'm chasing geese trying to raise the RPM. I was told it should run 7-1000, but it is running smooth at 4-700. I mean I'm probably getting better mileage, but something doesn't seem right. Any thoughts?
 
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Old 06-03-2018, 10:55 AM
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Warm engine, in gear, should idle around 600 or so.
 
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Old 06-03-2018, 10:56 AM
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Did you use an external tachometer, or are you relying on that guessometer in the dash to determine it's 400RPM?

RwP
 
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Old 06-04-2018, 12:37 AM
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Originally Posted by HeyYou
Warm engine, in gear, should idle around 600 or so.
Thank you she is idling perfect if that is the case! I need to fix my dif next. The pinion gear or bearing is definitely having issues.
 
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Old 06-04-2018, 12:39 AM
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Originally Posted by RalphP
Did you use an external tachometer, or are you relying on that guessometer in the dash to determine it's 400RPM?

RwP
I know, I can barely trust this dash. Since I replaced the TSS, the RPM gauge seems to be reading well though. Is there a free way I can get an exact RPM reading?
 
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Old 06-04-2018, 06:27 AM
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Originally Posted by Donovan Alexander Shovan
I know, I can barely trust this dash. Since I replaced the TSS, the RPM gauge seems to be reading well though. Is there a free way I can get an exact RPM reading?
Borrow a timing light....Advance or Auto Zone may lend them for free.
 
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Old 06-04-2018, 07:11 AM
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Originally Posted by Donovan Alexander Shovan
I know, I can barely trust this dash. Since I replaced the TSS, the RPM gauge seems to be reading well though. Is there a free way I can get an exact RPM reading?
TSS has nothing to do with the tach; it's driven straight off the ECU.

However, the frequency/current or voltage conversion is done by a board on the instrument cluster, and THAT can vary out of spec.

To get an exact RPM, borrow a real service tachometer. Do be aware that some tachs will have problems with a stable reading off the coil, though

You can cheat with a timing light; count how many flashes in 10 seconds, and multiply by 2, then the number of cylinders, and that's your idle speed in RPM.

RwP
 


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