inconsistant idle
 

I know that idle is probably the biggest issue people post about here, and I have read all relevant threads regading it, but I haven't seen anyone with an symptoms like mine. I have a s4 TII with all emissions stripped and a modded TB. BAC is gone, all solenoids are removed. I have a strange problem with idle. It is not bumpy, choppy, or bouncy like it is with a VAC leak or TPS misalignment. I have made sure there are no vac leaks and the TPS is properly aligned using a voltmeter. When I put in the clutch or come to a stop and let the revs drop, it may idle anywhere between 900(where I set it using the hard idle screw) and 1500. It is totally random. Also, occasionally it will fall on its face during decel when I'm coming to a stop. I just recently removed the dashpot thinking it may have been sticking, but the idle is still inconsistant. Is this a problem with the fast idle cam or the TB linkage? Perhaps a bad idle mixture or bad grounds? I have read about using the variable resistor to adjust the idle mixture, but have never tried messing with it. The car has newly cleaned injectors and a walbro fuel pump.

Thanks in advance.

I have an 87 TII and I am having the same problems , when I clutch my rpm's go up.. and sometimes it stays at a higher rpm till i clutch and release then it drops back to 750...i thought it might be a thermostat problem , but i replaced and still the same...i also have a coolant leak that is coming from somewhere above my intake manifold , but no matter how hard i look I cant find it.. .. starting to get really frustrated ...lol
any help would be greatly appreciated

I'm running with no thermo at the moment. Maybe that's my prob. I was thinking maybe the TB springs/linkage are dicked up.

I dunno.. right now I'm more concerned that she's dumping coolant everywhere...
But I cant find and cracked or loose hoses , apparently there is a small "L" shaped one from the TB that goes often but i cant find it...sigh

that small 'L' shaped hose is the 90degree coolant hose...It sits under the TB at the back of the engine. The hose routes coolant out of the rear iron and into your TB...


as far as the idle problem is concerned, i'm still dealing with my issues...lol

I dunno.. right now I'm more concerned that she's dumping coolant everywhere...
But I cant find and cracked or loose hoses , apparently there is a small "L" shaped one from the TB that goes often but i cant find it...sigh

sorry about the double post... I still cant find that hose .. I lifted her up and looked but still no luck .. unless its so obvouis that I'm missing it... or do I have to start unbolting to fet at it?

It's under the upper intake mainfold. You can't see it till you take it off. It may be blocked off. I believe you are referring to the hose that goes to the BAC valve, and if you don't have a BAC or if you're using one without coolant then it won't be there.

Can anyone think of any other reasons why my idle would be rock soild 850 then once the motor revs and drops back down to 1200? Do it again and it might settle at 1000. Fast idle cam perhaps? I'm tired of the car running like this, and am prepared to do anything to fix it. I'm tempted to buy another TB, but I would hate to spend money on something that is potentially not the problem.

Are these symptoms caused by a tired engine? The engine has 85-90psi en each housing still, but it has 145k on the clock.

mine does the samee thing n my enginee is rebuilt not too long ago wit 3mm apex seal, etc, but i think my plugs r fouling bcuz it is due.

I would suggest checking your TPS, BAC and for VAC leak, and ignition timing, and your plugs that mite be the problem according to the service manual, so use process of elimination.

I've already checked everything you suggested except timing which I will do soon. Once again, there are NO VAC LEAKS AND TPS IS PROPERLY CALIBRATED.

Just a guesss here, but can you put the BAC back on? That component contributes to air intake for idle speed control from what I gather from the TSM.

I've tried connecting it without the coolant lines, but it wants to do the AWS Accellerated Warmup System When it's connected, and screws up the idle even more. I have the stock ECU.