Is This Idle Hunting? Bad Idle.

[delljit]

Some small facts first off - r33 gtst s2 (1996) with no mods apart from apexi pod.

I recorded a video using my mobile phone so the quality isnt the greatest. Ill try to provide an explaination to help.

http://www.youtube.com/watch?v=02Cyv2CWqDU

In the video you can see that my idle is fluctuating from about 100-1000rpm. This occurs when ive been driving the car for around 5-10 minutes, or generally once its all warmed up properly. You may also notice that as the rpm fluctuates, so does the vac/boost.

About 3/4 through the video you can see me open the throttle a little bit. The following is what i deal with on the roads when driving. Say im in second and approaching a corner or roundabout and have to give way so i slow down. Its very likely that the car will completely drop off all rpm and die on me. In the video im in neutral or first with the clutch in i forget. Either way, when im in first and i start to slow down a bit after opening the thottle, its very likely that the rpm will drop off to around 0 but not actually stall completely. As seen in the video i rev it a bit, then the rpm drops to about 0 and the battery light flashes for a second but the car doesnt actually die.

Anyway, i plan to take the car to a workshop/garage this month to solve this issue however if i can do this at home id be excstatic.

After searching the forums heavily ive come to the conclusion that it may be caused by one of, or a combination of the following:

-faulty afm

-leaking i/c piping

-dirty aac valve

-faulty o2 sensor

-faulty tps

Ive read that cleaning the aac valve can do wonders; is this the type of problem i can solve by cleaning the aac valve at home? It's just that i dont have a large amount of cash to wave around so being able to fix this my self would be great.

[OVADRV]

it could be dirty or faulty AFM. give it a clean with electrical contact cleaner to start off.

[NYTSKY]

I had this problem,turned out to be the ACC valve,dont bother cleaning it,it didnt work for mine as it was stuffed.

Not saying this is your problem.

[frozenwaffles]

yeah that looks very air flow meter'ish...

[jeffworld2]

if not a factory computer, this can be caused by having the first few cells of the map unbalanced, ie on powerfc first 3x3 should be the sameish in fuel and timing, otherwise you get this sort of thing as it jumps through bouncing off different values.

if standard ecu, check your afm wiring and plug, and if all good try cleaning or getting a replacement aac valve

[bazr33]

mine did this when rolling up to a set of traffic lights in neutral

it was the AAC valve. You can check this by temporarily disconnecting it. if ya idle doesnt fluctuate after disconnecting it, well theres ya problem

i ended up putting on a sr20 aac valve that was apperantly the same and doesnt do it anymore.

[Hydroxinol]

I had the exact same symptoms as you after pulling everything apart for a turbo upgrade (pulsing idle when stationary with car warmed up). In my case it turned out to be an air leak. Check all vacuum hoses connected to the crossover pipe and intake manifold for broken/split ends. Also check your Intercooler piping and make sure there are no leaks after the AFM. Definitely clean your AAC Valve regardless as many have mentioned.

[delljit]

Gave the AFM a good clean today, the inside was full of black shit. Gave it a clean with some electrical contact cleaner and put it back, the car seemed to run better than before. It still has a rough idle at times but its not as frequent.

Tomorrow i'll be cleaning the aac valve, hopefuly that helps.

[Hydroxinol]

In the video you can see that my idle is fluctuating from about 100-1000rpm. This occurs when ive been driving the car for around 5-10 minutes, or generally once its all warmed up properly. You may also notice that as the rpm fluctuates, so does the vac/boost.

I have the same thing. At first I thought it was a Vacuum leak, but after testing with soapy water and listening with a hose I found nothing. Now I suspect it is a faulty O2 Sensor. When the car starts idle hunting try disconnecting your O2 Sensor and wait around 30seconds. When I did this my idle stopped still at 900rpm.

My theory is that the car runs fine until the O2 Sensor is warmed to operating temperature as the ECU ignores this reading until that time. Once the O2 sensor is operating, the ECU reads a false value and idle struggles as the O2 Sensor is not able to keep the ECU up to date with accurate readings. I tested my O2 Sensor at operating temp with a multimeter and noticed that it does not vary in voltage as it should. I am going to test another O2 Sensor. Will let you know how it goes.

[delljit]

Very interesting theory. Last week i gave my aac valve a very good clean. At first it seemed like the problem disappeared but after about 30min of driving it happened but only to a small extent. No where near as bad as it was before. The aac valve cleaning definately helped.

Unfortunately, i havent been able to drive my car enough to see if the problem has gotten any better. I got busted driving it last week and got 2 fines, one for it being manual and the other for high powered vehicle (im a p-plater). Its my second car and i drive it like once a week but i dont feel like risking more fines. Im fully licensed next month though.

The o2 sensor stuff sounds like its worth a try if it happens to me again, ill keep it in mind.

[eddieeeee-ro]

try a new afm.

[tek_01]

thats how my car was running when i took the BOV off and turned it on LOL

so definately check for leaks in all piping such as vacuum and intercooler/intake side of things

but as others have mentioned before try someone afm