Cause of an issue???

[boojak87]

Hi all. Just wondering whether a stuffed Throttle Position Sensor, Idle Air Control Valve and/or Mass Air Flow Meter Sensor could be the cause for a rough idle when sitting at lights in gear and slightly poor fuel economy? I'm sort of relunctant to try absolutely everything that someone's mentioned to me, because it could be a never ending thing until i replace practically everything in the engine! Just wondering what you all think:

Symptoms on my Ecotec VS being:
- Rough idle ONLY IN GEAR, when in 'N' and 'P' idles smooth. The idle doesn't drop, (hovers around the 800rpm mark) and doesn't threaten to stall at all, however the car has a constant rumbling feeling when sitting at the lights (like sitting in a carby v8), the slightest acceleration (even just 100rpm more) gets rid of it and it's smooth again.
- Poor fuel economy (hovering around the 14.5L/100kms area) was up to 15.5L - 16L at a stage before injectors were treated with a bottle of injector cleaner.
- Not the greatest of pickups (especially once engine and fuel is warm), almost sort of hitting a flat spot in 2nd, when going between 2000 to 3000rpm, then you get jolted back into your seat a tad more once over 3000.
- Don't know whether this is significant or not but after a night of sleep and awakening on a cold morning first start-ups can be a tad rough. It starts almost instantaneously like normal but it chugs for a couple of seconds before it revs itself up to 1500 for a little before finally settling to normal idle speed. When outside of the car during the first start up on a morning a ticking noise can be heard from the engine for the first 30 seconds or so. Like i said, i don't know whether this is significant or not but just thought i'd mention it as the more information given, the better.

Just another query, could the catalytic converter be the cause of this, i have stumbled across the theory once or twice but, i'm unsure!

Thanks all, any feedback or general comments on what i should get checked would be awesome.

Thanks again, Boojakz.

[kopper69]

Mate your thinking of all the expensive stuff. Start cheap. General service is always the best place to start. It doesnt get much cheaper and it will solve most of these little problems. If it doesnt, the car will run better anyway. Things like coolant, oil and filter, fuel filter, spark plugs. Do a search and find out how to check spark plug leads too. They are only $50 or so, so it might just be worth getting a new set. You can clean the throttle body for a bit over $15, so if you have the time and patients you might as well give that a go too. Do the service first. As i said, its cheap, its easy and it will only take a few hours at most.

[boojak87]

Originally Posted by kopper69

Mate your thinking of all the expensive stuff. Start cheap. General service is always the best place to start. It doesnt get much cheaper and it will solve most of these little problems. If it doesnt, the car will run better anyway. Things like coolant, oil and filter, fuel filter, spark plugs. Do a search and find out how to check spark plug leads too. They are only $50 or so, so it might just be worth getting a new set. You can clean the throttle body for a bit over $15, so if you have the time and patients you might as well give that a go too. Do the service first. As i said, its cheap, its easy and it will only take a few hours at most.

Sorry mate, i forgot to mention stuff i had done! MY bad...Lol okay.

Things done:
- Complete service done less than 1000kms ago
- Replaced leads with Top gun leads
- Had throttle body cleaned during service
- O2 Sensors replaced
- Dose of injector cleaner 2 tanks ago

I'm unsure if the oil and fuel filters were replaced though.

[hako]

Try changing that fuel filter and it may be time to bite the bullet and get the injectors cleaned by removing and getting them professionally cleaned - the fact that a can of cleaner lifted your fuel economy sort of points that way.
Also possibly the fuel pressure regulator may be stuffed - not sure on how you test them (do a search). Good Luck.

[digisol]

Most likely the oxygen sensors, $$$ little buggers and you need two of em on a VS, the bad fuel economy kinda gives that away, remember they can be 90% stuffed but will not show a fault code until 100% stuffed.

Test the codes anyway just to be sure, they will make it idle rough, miss and fart and use a heap of fuel.

[boojak87]

Yeah had the O2 sensors (oxygen sensors) replaced about a month back so definately not that! Will get a quote on replacing injectors and possibly replacing engine mounts tomorrow. Any more ideas welcome.

Thanks again guys,
Boojakz

[digisol]

Having a full wallet sure helps when tracking down a small problem, so many things can go wrong.

At least when you find it, all the other stuff will be new.

Fix the simple stuff first, fuel filter etc.

[boojak87]

Got a quote of 130 bucks to replace injectors. Just decided to let yas know, i drove dad's vt around all day today, and the power difference (even though they're the same engine) is incredible. Mine runs like a piece of poo compared to his, hopefully the injector change-over should get my baby vs running like the vt is (nice and smooth and powerful). Now all i got to do is find a set of injectors.

Cheers all,
Boojakz

[hako]

Don't forget to post back when you get the injectors cleaned Boojakz, we'd all like to know if its worth doing.