p0wp0w

When I first bought the car it would have an occasional hiccup at idle, just for little bit at a time but you could tell and you could hear it. It would idle perfect and then drop down to almost deing and then come back up to regular and keep doing that for a while. Driving the car is fine, but the idle would just keep hiccuping.

I added the Guru chips and that fixed it, maybe every once in a while like once a month or so. Then I added the MAP stage I kit and it was fine and now I added the Tial. A couple days after the Tial the hiccupping started again. I found that if I run full speed and hit full boost, idling afterwards would be very hiccuppy. But it would be for a long time, most of the time till I shut off the car. The car runs fine but at idle its very noticable. After I shut off the car and wait and turn it on, it would go away but sometimes still be there.

Does anyone know what causes the hiccup at idle, its very annoying and I don't know if it means my engine is dying or not. Thanks alot!

p0wp0w

bump!

Danno

Have you tried sugar under the tongue or sipping water while holding your nose?

What do you mean by hiccup? Does the car shake a little? Does the idle-speed drop?

If you have an air-fuel gauge, you might see that the hiccup occurs at the extreme ends of the dithering range. Like at the extreme rich or lean end. The way around that is to adjust your idle-zones in the MAP computer to either lean out or richen the mixture depending upon which end of the dithering caused the problem.

Another possibility would be the idle-stabilizer valve. Disable it at the test port and uncrew the idle-aduster screw on the throttle-body by about a 2-3 turns. The top of the screws should be just about 1mm under the top-surface of the hole it's in. This adjustment makes the idle-stabilizer contribute 0% to idle air, thus it can't mess with you.

p0wp0w

I just usually drink water upside down or drink it really fast! :P

The car does shake just a little though, the idle-speed either drops then comes back up really quickly or it jumps up to a little under 1k RPM and then drops back down to regular ~840RPM really quickly.

The Tuning module says that I'm still in zone 305 when that happens and the A/F gauge in the tuning module doesn't change when it hiccups, it just dithers around .75-.80 and sometimes goes down to .5

I'll try the idle-stabilizer thing, but I was wondering how do you unscrew the yellow screw, it looks like a circle on top...

Thanks alot Danno!

Danno

That mixture looks a little rich. Try subtracting about 2-3% from zone 305. With the car fully warmed up, it should dither from 0.45 to 0.55 volts centered on both sides of 0.5v. The richer mixture may be causing your idle to creep up, then the idle-stabilizer cuts back to drop it, which is what causes that little hiccup. Idle drops and the stablizer catches it at 840 and the cycle starts all over again...

This rhythmic cycling of the idle-speed can also be caused by vacuum leaks after the throttle-body. You can test this out by disabling the idle-stabilizer via the test-port. Then adjust the idle-screw to the setting above (you might have a cap over yours). If your idle is faster than 900rpm, you've got a vacuum leak that's sucking in extra air somewhere.

cpt_koolbeenz

Any ideas on getting the idle screw to stay put? Today the car started to idle at 2200 RPM. I thought it was the ISV acting up but I found the idle screw about 3 turns out from what I had set it at. The screw was gradually unscrewing itself but the ISV compensated for a time, but all of a sudden the idle just jumped to 2200.

p0wp0w

ooh alright,
so at idle I'd want it to be a bit leaner, but at speed I want around .80 right?

Thanks alot

CPT have you tried some Tite'n from Loctite or something along those lines? I havn't needed to use it yet but that might seem like it would work..

facboy

really danno? 'cos my screw is a fair way inside 1mm (i think maybe around 4-5mm?). if i were to pull it that far out, i reckon my idle would be around 3000 rpm!

washington951

just take a little bit of RTV sealant on the tip of your finger and then slide your finger across the top of the casting for the screw - it'll stay put and keep the screw in its place, but can easily be removed if needed.

if i remember, isn't there supposed to be a rubber gasket on that screw, too? is yours there?