Intermitten Low Idle

[gobagheera]

I have a 96 GTS.

Most of the time, the idle is solid at ~450rpm, but every now and then, when I come off the throttle, it'll drop to 0 and bounce around 100rpm. It has never died on me, but I was alarmed when it did this. It'll slowly creep up to 450rpm from there. If I blip the throttle, it'll settle on 450 and be fine.

Is this a problem or an indication of potential problems? Or is this normal and I'm just being paranoid? Thanks!

[BOOST ALMIGHTY]

I doubt anything is really wrong, but it probably wouldnt hurt to stick some spark plugs in it.

[viper spray]

And replace the IAC .

[gobagheera]

Thanks for the tips. I will give those a shot. I was secretly hoping this was normal. At least it doesn't seem major.

[GTS Dean]

The first tic mark on the tach is 500 rpm, not 0.

[99 RT/10]

Start with cleaning the IAC and Throttel bodies, should not need to replace the IAC, BUT you might want to think about replacing the battery. A low or bad battery plays havoc with these cars computer.

My 96 did th esame thing(coming up to a light or pushing in the clutch). I disconnected my computer to reset it(about 20 minutes) and that also helped, but a new battery(while reseting the computer) worked perfectly.

[ram4whldr]

Originally Posted by GTS Dean

The first tic mark on the tach is 500 rpm, not 0.

That is what I was thinking. So it is probably idling closer to 650 - 700.

[gobagheera]

I'm pretty sure I have the ticks on the rpm gauge correct. After warmup, it idles just a hair below the tick between the 0 and the 1 marks (which I presume is 500). When it falls to 0, it goes to the tick with the 0 mark on it. Please correct me if I'm missing something on the rpm gauge.

Thanks for all the input and ideas. Got a lot of things to try

[99 RT/10]

O tick=0
next tick up= 500 RPM(same size tick)
next tick(Smaller)= 750 RPM

It should idle just below this smaller, third tick mark. Hope this helps.

[gobagheera]

Originally Posted by 99 RT/10

O tick=0
next tick up= 500 RPM(same size tick)
next tick(Smaller)= 750 RPM

It should idle just below this smaller, third tick mark. Hope this helps.

Wow, didn't even notice that 500rpm tick. Thanks. I would have never known. Wish they would have made the tick distances proportional to make it clear what rpm it was at.

So I guess it was going from 500 to 750 rather than 0 to 500 that I thought. I'll try the tips above to see if I can stablize the idle still.

[-FROG-]

Originally Posted by 99 RT/10

Start with cleaning the IAC and Throttel bodies, ....

My first thoughts too.

[kenschobert]

my 1996 gts idles at 500 rpm

[95Viper]

Exact thing was happening to my 95. I removed the IAC, then it can be taken a part in two pieces and cleaned the heck out of it. Then I opened the butterflies on the TB's and cleaned very well, even with a toothbrush to ensure a ridge had not built up and the TB wouldn't close cleanly. Ran perfectly as soon as I was done.

[Jack B]

Originally Posted by gobagheera

Wow, didn't even notice that 500rpm tick. Thanks. I would have never known. Wish they would have made the tick distances proportional to make it clear what rpm it was at.

So I guess it was going from 500 to 750 rather than 0 to 500 that I thought. I'll try the tips above to see if I can stablize the idle still.

Basically all of our cars idle at 680-700 - Even when the idle seems erratic it holds in that range. That is where the PCM keeps it. Take one plug wire off and it will still idles in that range. The PCM via the IAT and timing advance keeps it in that range.