VS ecotec Bad idle and missing while cold, and running rich.

[Robb]

As the title states, recently my 95 acclaim is running rich all the time it seems, I'm assuming this because of the smell of the exhaust and increased fuel consumtion. I've gone from averaging about 8L/100km to about 10-12L/100km (I do mostly country driving).


Also to start my car (when cold) I need to give it a slight amount of throttle, otherwise it will just start and then stall instantly. Then when I give it a bit of throttle it will just seem as if it misses for the first second before it decides to move.
Once the car is warm, or if it was only off for a short period of time, it no longer misses at all and the idle is fine, the car behaves great (other then bad economy).
I have tried opening the t/b butterfly slighlty, that fixes the stalling on startup (not the missing), but means once the car is warm it idles way too high.

I have checked the ecu for lodged codes, I only get 12's, so all is fine there.

I have ruled out
- spark plugs
- leads
- tps
- iac

I've ordered new O2 sensors, and if that does not fix the problem I'm thinking new coils and dfi.
I tested and inspected coils and dfi and they seem fine, but reading other threads it seems other people have tested and inspected the coils and dfi and it still ended up being the problem.

So do you guys think I have missed something or know what the problem is?

[RX25SE]

You will barely notice faulty O2 sensors as they are a fuel trimming device (small adjustments from a base program)

I would be taking a good look at your Air Mass Meter.


Dont mess with the throttle stop screw, this will upset the base idle settings.

[Robb]

I gave the MAF a good clean with MAF cleaner a couple days ago, as it was not clean but it was not dirty enough to cause any problems. But after it was clean there was no noticable change

[Wombles]

Maybe try the CTS?

[Robb]

Thanks, did not think of that. I might replace the cts and check it's earth before I replace the dfi and coils as the cts will be much cheaper lol (I guess around $20 for a new one?)

[RX25SE]

CTS is worth a shot.
It's not earthed as such.
The PCM sends it a 5v(IIRC) reference voltage, as the CTS has a neg temp coefficent, the voltage back (signal)to PCM varies with temp.


I doubt it's ignition. This would normally cause issues on one cylinder or cutting in and out.

Most likely fuel system.
Have you checked the fuel pressure reg? Is it bleeding fuel in the vacuum line?

Badly leaking injector? (normally a missfire symptom)

[Robb]

In regards to the fuel system being the problem, is that still a possibility when the car acts totally normal* once it warms up?
*excluding the smell of the car running rich and increase in fuel usage compared to a month ago

I also replaced the injectors about 5k km ago

[Wombles]

Try cleaning the I AC?
Test the TPS?
Test for a misfire?

[Robb]

In regards to the IAC and TPS, I have working spares, tried them, no change.
I'll work it out eventually, most likely after some sum of money

[Wombles]

Try testing the CAS to.

Just throwing ideas for ya..
Have a similar problem. Changed heaps of things but still slightly there..

[Robb]

Well I seem to have fixed 90% of the problem, once the car has been running for 10 seconds it behaves fine.

The battery terminals must have been slightly corroded, although visually it was barely noticeable, therefore it did not seem like it was major enough to effect anything, and why I have not bothered in doing this in the past.
But I thought I might as well give it a sand and a wipe down because I have tried everything else. Then problem pretty much solved. No missing under acceleration when cold, and after 10 seconds or so the idle is fine.

[Brett_jjj]

A while back I had bad misfire problems when starting my VS ecotec from cold. When the car was first started for the day it would miss badly would and barely idle unless it was revved a bit..Usually the throttle doesnt even have to be touched at all when starting, hot or cold. It would only do this for 20 seconds or so, then it would clear itself, come good, and idle perfectly. It didnt happen at all though once the engine was warm. I ended up tracking it down to being a faulty purge cannister soleniod. Its located at the rear of the engine on the drivers side.