[bron5on]

Hey guys, hope I'm not rehashing old topics but I have a problem with the idle in my g16 16v (from 95 swb vit) converted sierra. The problems seem to stem from cold starts. When I first start it will idle at around 1100rpm, over the next 5 mins it slowly climbs to about 1600 before eventually dropping to 1000. I assume this is when the thermostat opens. How ever, if I don't give it the full 5 minute warm up before taking off, the idle stays high. Every time i pause at intersections or coast with clutch in the idle sits as high as 1900 rpm, sometimes alternating between 1500 and 1900 (as if I'm revving it). Quite odd really. Even half an hour later it will still idle at 1500 unless I pull up somewhere and let the car idle for a minute or two at which point the idle will drop back to 1000 and wont give me any problems until the next cold start. Figured it may be the IAC(?). I looked this up on outers and found this pic:

Apparently plug 40 is the IAC? Mine however looks like this:

As you can see, the plug itslef exists on my loom but has nowhere to go on the manifold. I'm using the original loom that came with the engine. It seems the plug has never been utilsed so is my model different> Am I looking at the wrong part? What is the black plug above it? Also to the left there is a blue plug (behind the throttle cable), Is this what I'm looking for? Any help would be much appreciated as I'm at a bit of a loss! I also tried dissconecting the temp signal for the ecu. Whilst warming up it makes no difference if it's dissconnected but once up to operating temp when idle has dropped, removing it sends the idle back up to 1500rpm. Once I plug it back in it takes just over a minute for the idle to return to normal. Let me know if there are any more pics or details I can provide. Thanks in advance


Bronson

[11_evl]

the black plug is the TPS throttle position sensor.
i could guesstimate the rest but ill leave it to others who may no better

[bron5on]

Thanks matey. That was actually my guess too. Think I'll just have to pull the whole lot apart, clean it and hope I can get it back together in the right order!

[royce]

mine had the same prob, plus low on power and crappy fuel consumption

2 things I did at the same time that solved it, were clean the airflow meter with contact clean and go round and make sure all the vacuum hoses and connections were solidly airtight

straight away fixed the prob, dropped near on 3l/100km fuel usage and drove heaps better, I dont know if it was one or the other or both that fixed it though

the IAC is round the other side of the manifold, unplugging it will only tell you if the computer is making it idle high and not something sticking

[ninjadaniel]

Your TPS (Throttle position sensor) directly controls your ignition timing advance. Check the resistance over the pins for this, your base-line (no throttle) should be a certain resistance rating, if this is incorrect it will advance your timing and cause increase in idle speed.

Try disconnecting battery for 15 minutes to reset ecu

[brendan]

my G16B always cold starts at 1500rpm untill warm then its drops to around 900-1000rpm. the guy ni bough it off said it was normal/way ti was hooked up sort of thing. but yer i might go around with some soapy water and cheak all the vacume conections

[bron5on]

Thanks for the answers guys. Am going to have a play with it today. Will disconnect the battery and have bought a few metres of vaccuum line so I'll replace the lot. Might even pull the throttle body and give it a bit of a clean. Hopefully I can get it back to normal. Was fine for the first 5 momths after the conversion and only started playing up a few weeks ago. Will see how I get on!

Cheers!


Bronson

[bron5on]

Been tinkering with the zuk and was wondering if this is my IAC?


It's from the inlet plennum on the engine side. You can see it in one of the earlier pics with the blue elcetrical plug connected. The top pipe is an air line coming from inlet tract, midway between throttle and air flow sensor. The bottom two are water conections which leads me to believe it's temp controlled. I tried blowing through the water lines but it seems to be very restrictive. Could there be a blockage here causing the valve(?) to not operate correctly thus resulting in the idle problem i'm having?

[royce]

yep thats it, from what I gather its opened when cold to give fast idle for warm up then the coolant flowing closes that and the ecu takes over the idle speed control

not sure on restriction, better to see if both hoses get hot when up to temp

[bron5on]

Beauty! While it was off I gave it a hit with the compressor and noticed it was somewhat easier to blow through afterwards. So I bolted it back on and replaced the vacuum lines while I had the bonnet up and so far it seems to have done the trick. Will find out over the next few days i guess. Has anybody had experience with these? I would imagine there is a better way to clean it rather than just hit it with the compressor? Cheers!

Bronson