1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Rough idle, sometimes dies when coming to a stop

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Old Feb 21, 2020 | 01:17 PM
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Mr. E's Avatar
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From: Illinois
Rough idle, sometimes dies when coming to a stop

Hello all,
Just got a 1985 rx7 GS with a GSL LSD on Monday. Loving the car so far, just come across an issue.
The car starts right up and drives good, the problem comes when the engine warms up and goes to idle, it drops to around 200 rpm and sometimes dies at that point. If I give it gas it doesn't die.
Any thoughts on what this could be? I replaced the spark plugs and wires, but that didn't change anything. My gas pedal is a little loose too, not sure if that maters.
Thanks for your help!
(side note, but my rear passenger side is making a lot of noise, pretty sure thats the diff mount tho)

Also here is a video after a cold start, about 30 degrees out today: https://www.youtube.com/watch?v=r96s...ature=youtu.be

Last edited by Mr. E; Feb 21, 2020 at 01:20 PM.
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Old Feb 21, 2020 | 03:46 PM
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Have you tested for vacuum leaks? Will it ever idle down and stay running? Has the fuel filter been replaced? And are the float bowls filled half wayish at idle?

The idle and or timing may be off too.
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Old Feb 21, 2020 | 04:49 PM
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I haven't tested vaccum leaks, I will replace the fuel filter and check the floats, it doesn't stay idling at 200 it kinda stumbles and either dies or goes back up to 750 or so.
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Old Feb 21, 2020 | 05:19 PM
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Originally Posted by Mr. E
I haven't tested vaccum leaks, I will replace the fuel filter and check the floats, it doesn't stay idling at 200 it kinda stumbles and either dies or goes back up to 750 or so.
RE:checking floats...look at each float bowl window,fuel level should be 1/2 way up in window. If one or the other is higher,look at venturies on that side and see if fuel is dribbling out. DON'T try adjust floats at this point.

Th 1200 rpm idle,is that with choke pulled out? The shaking could be from secondary throttle plates not quite closed from dirt/gunk buildup or a misadjustment. Have you tried to adjust base idle?

Adjust base idle screw until engine running @1000rpm. Adjust mixture screw richer til rpm picks up @2-300 rpm. Adjust idle speed screw to @800 rpm and see if carb will hold that rpm. Drive car til good and hot and see if it will maintain that rpm. If it does,check and set leading and trailing ignition and reset idle speed. Target rpm is 750.
See where you can get with making these basic tuning adjustments before you start tearing things apart and see what you can find.
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Old Feb 21, 2020 | 05:29 PM
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The drop to 200 rpm only happens after the engine has warmed up and the choke has gone back in. I will check the floats and try some of the tuning tips you gave me on sunday cause I'll have a lot of free time and the weather will be really nice. Thanks for the feedback so far, I really appreciate it.
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