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VT V6 high idle issue

No9

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Help needed with high idle issue. When the car is started it revs to around 2000 rpm and then slowly drops to 1200 rpm in park,when its in drive it stays around 1100 rpm and runs rough. I have cleaned the throttle body,replaced iac and tps,checked for air leaks changed temperature sensor and tried the idle re-learn procedure and nothing is working. Any advice would be much appreciated as i'm loosing my mind lol.
 

BowTie

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Tb butterfly can get sticky when old and not close properly. Try pushing the tb closed by hand while it's idleing.

Have you played with the idle screw? That can cause it too.
 

Andyman022

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Help needed with high idle issue. When the car is started it revs to around 2000 rpm and then slowly drops to 1200 rpm in park,when its in drive it stays around 1100 rpm and runs rough. I have cleaned the throttle body,replaced iac and tps,checked for air leaks changed temperature sensor and tried the idle re-learn procedure and nothing is working. Any advice would be much appreciated as i'm loosing my mind lol.
 

Andyman022

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Sorry bout that no9 I’m new to this site it just so happens that I had the same or very similar I am a qualified mechanic but hadnt worked on a commodore since VH era but I also have a vs serious 2 wagon (For Work) that I have had for about seven years. And basically I have set it up as a tow vechile and it’s got a trailer on it more than not, (been great).just bare with me for a minute and I will get to what I needed to do only a couple of nights ago I was using a mechanic mate of mine to look after it for me as I work in a different industry now, until about 12 mths ago I wanted to get the heads done on it and with out a second thought he said yeah there probably........ by now it has done a lot of Kim’s and I only wanted to do the heads to give me more torque l knew they weren’t.......after he had done the heads my car has never been the same, I will tell you that the head work that I wanted done should have given me plenty of more towing capacity, I then started questioning his capabilities and removed the heads thinking the worse case but they were to the specifications I asked. Since then I have been stabbing in the dark. The last couple of months my car started using more fuel but and when starting to stall every now & again. When starting in the mornings it was doing exactly the same. At this stage I really knew nothing about ecotec engines. But I tell you now that Without tooting my own horn I know every ......... thing about the running of them. don’t get me wrong I knew what to do with the Dynamics for head work, but compared to the amount of sensors on these ........ EGINES the heads were easy, last week I drove about 75kls towing an empty trailer & went through $40 of fuel, the next day same thing. I was starting to Dreed driving it. At my wits end I left work on last Wednesday at lunchtime as it was pissing me off big time. I had discovered this site and was reading a lot about people that had the same problem quite a lot. And honestly I was fearing the worded, but do not go done the same road as me and believe that everything on here is factual. No offence to this site it did help me quite a bit & a lot of it was around 2013/2015. So really not a lot of people knew about every sensor, some knew a lot about a sensor. I needed to go through each one myself as I had had a gut full if you believe everything thing you read you wil rebuild your whole car, as l basically did I started working on the issue around 12:30pm & gave up around 4:30am the next morning had basically taken out every sensor and worked out what each ones purpose was spent about three hours at my second home (Car Wreckers) im going there again tomorrow, not for my wagon thou it’s run great now as I also have a statesman that I play with (jazzing up)as my fun car, trying to compare what the sensors are supposed to look like. I only gave up as I needed to go to work in two hours. Sorry for banging on, lm writing all this so that you do not do the same there are too many sensors to go on about at this time because realistically I haven’t had a lot of sleep since but I will say that your car is not ........ you will be able to fix it, I wil start by asking how many k’s has it done, is it using more fuel than normal & last but not least is the exhaust tip black as black can get, mine was spitting black soot all over the front of my hammer tone silver trailer. I ask these questions as If so you might have an injector o’ ring not sealing or I did notice that the wiring loom for the injectors on the passenger side were sitting pretty close to inlet manifold under the throttle body & gets pretty hot every time I tried something I’d move the wires by accident and at one stage it receding up to around 3500 with no insulation hey try looking for those sorts of things as a leaking o’ring that’s how far I went also I replaced injectors & everything to no evail, it bought back my basic instinct that it’s normally the most simple thing that gives you the most grief, one more thing before I fall asleep in my shed do you know much about cars if you do l will probably be able to walk you through it, I’m off to bed now as I want to get up early to go shopping for my statto cheers Andyman I’ll check in tomorrow I just read back through it & it’s .......... long post sorry bout that.
 

NeddyBear

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I was only looking at my RPM yesterday, she purrs at 600 RPM in park.
The cause of your issue could be endless and would depend on your maintenance program as to whats been serviced and replaced.
Just a few points that might need attention: have you replaced the throttle position sensor, spark plugs and leads.
Five years ago our old girl was running a tad rough and after replacing these she started purring again and has continued to do so.
I think over the 10 years I've replaced all the sensors and fuel related thingys so maybe that's helped her to continue to run smooth.
Another thought hows the fuel injection components, a few years back I freshened up this entire area that made a noticeable difference straight away. Could even be the idle speed motor/air control valve.
 

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No9

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So far i have replaced the injectors and also a complete inlet manifold gasket set,iac,tps,plugs,leads,coils and module plus fuel pressure regulator. The car starts at around 2000 rpm and drops down when warm to 1100,i can not find any vacuum leaks and the fuel economy seems ok but the exhaust tip is black and smells rich. I have cleaned the throttle body and plenum and replaced the pcv. I also replaced the fuel pump,the engine runs well for having 205,000 kms but i'm stumped and can not get the idle down. I'm fairly competent with mechanics and appreciate the help and suggestions you guys have given me.
 

Andyman022

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Hey there No9 I worked out while changing of cleaning all o the sensors you’ve mentioned that my idle & the running of the car in general didn’t really change that much, until I was driving it from work, I pulled over For a breather & was looking under the bonnet, still stump, I realised which I have not read posted is, what it needed maybe the ICU needed reset. So I disconnected the neNegstive battery terminal for just over 30 seconds, then let it idle for a minute or so, drove it normally for ten minutes, pulled over & turned it off, restarted it & drove the rest of the way home & man it was like driving a totally different car man, yeah sure I hade to reset my stereo settings. But compared to the stress release OMG. The car is still running awesome, in my last post I mentioned to fuel consumption ($40 for 70ish KLm’s) after reset I’ve done the the same trip and used not even 1/8 of a tank & idles great. So maybe give that ago hey. (I think after all the work I had done the EXU thought WTF & gave up trying :) hey) don’t blame it was about to cheers Andyman
 
J

JohnW

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So far i have replaced the injectors and also a complete inlet manifold gasket set,iac,tps,plugs,leads,coils and module plus fuel pressure regulator. The car starts at around 2000 rpm and drops down when warm to 1100,i can not find any vacuum leaks and the fuel economy seems ok but the exhaust tip is black and smells rich. I have cleaned the throttle body and plenum and replaced the pcv. I also replaced the fuel pump,the engine runs well for having 205,000 kms but i'm stumped and can not get the idle down. I'm fairly competent with mechanics and appreciate the help and suggestions you guys have given me.

Check if any error codes have been recorded (some important ones don't turn on the engine light), and no matter what the fault rectify them as a starting point. Might not fix your problem but at least you'll know your're starting your search from a reasonably solid base.

Once you've done that and the problem persists, from the symptoms your describing I'd be having a close look at the engine temperature sensor (I'd just replace it, about $25). If its inaccurate and telling the ECU the engine is cold then its going to raise the idle speed and richen the mix.
 

No9

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Thanks guys i have checked for codes and nothing was logged,i also replaced the temperature sensor. Would bad o2 sensors cause high idle?The only other thing i can think of is the maf sensor which i have cleaned.
 
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JohnW

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I know this is probably a really silly suggestion, given all the things you've already done. But as don't think it got a mention so far might as well chuck it out there.

Dodgy air filter or a blockage in the air intake pipe to the filter box?????
 
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