ECU? Memcal? Economy and rough idle?

[boojak87]

Howdy all,
Just a quick question. I have a 96 VS V6 ecotec sedan and for a while now i've have noticed a lack of economy, pulling 15.5L per 100kms on average for the last countless amount of tanks (granny driving). Quite a while back, (before the car was handed down to me) we noticed a mean rattling sound when slightly accelerating uphill. We were told it was a timing issue and to try switching to premium unleaded fuel. We did so and never heard the noise again and forgot about the problem. The economy and the MEAN idle i get sitting at the lights hasn't really bothered me until now (as petrol prices are going up and i'm often paying $70 (on a cheap day) to fill up on a student's part time wage) and i was just wondering by chance (don't know much about the computer system in a VS) if the ecu or memcal was rooted, thus giving the previous timing issue, the rough idle in drive (sitting at lights) and the poor fuel economy? If so, could it be pinpointed to either the ecu or memcal? I'd much rather pay for a new memcal than fork out a heap for a whole new computer! If it is just the memcal, do you guys recommend i get a performance chip as i have a few mods (top gun leads, ss inductions cai, catback exhaust) and am planning to add things like extractors and high flow cat soon. All your input would be much appreciated including ecu specialists like Dr.Bob.

Thanks all,
Boojakz

 

[Doctor Bob]

get me the code off the original memcal, there were some pinging issues with some standard vs ones.

Rob

 

[kopper69]

Mate your thinking ahead wayyyyyyyyyy to far. ECU is the last thing you check. You havent checked anything yet by the sounds of things - Dont start at the high price items and work back. There are so many things which can cause a rough idle and most checks can be done free. I would place a bet that a rough idle is going to be a loose or bad spark plug lead or spark plug. Do yourself a favour and replace the spark plugs first. Get a multimeter and make sure the leads check out ok.

http://forums.justcommodores.com.au/showthread.php?t=22308

Make sure the connections are tight. I reakon that the problem will be that they are loose on the spark plug. Push them on and you will probably feel them move around. I found i had to warp some of the connectors slightly out of shape so that would make a tighter connection on the spark plug. Check for fault codes as well. Try this, let us know how you go and we will work on if the problem isnt fixed.

 

[boojak87]

Ok...lol here we go...things done during recent major service:

1) O2 Sensors replaced
2) Throttle body and IAC cleaned
3) Complete fuel system check for leaks
4) Leads and plugs checked and replaced (replaced leads with top gun)
5) Air filter replaced
6) Fuel filter checked
7) The usuals like oil etc.


Possibilities that may cause the problem i have:

1) Injectors (never been cleaned or replaced in 217,000kms)
2) Engine mounts (possibly causing rough idle feel) (have been told they're on their last legs)
3) Exhaust leak through manifold or cat clogged up or just rooted??? (Again, never been replaced or looked at)
4) ECU/Memcal, had a ticking noise in engine a long time ago, when accelerating even slightly uphill, went away after switching to premium unleaded. Took the car to the mechanics and was told it was a timing issue and premium burns at a hotter temperature, thus the noise disappearing.

The car actually does idle fine (sits at steady idle revs right between 500 and 1000), it doesn't feel as if it's gonna just conk but it does send a mean vibration through the steering wheel when sitting at the lights. Another thing is...on first start on some mornings, backing out the driveway, then flipping to drive and turning wheel and just bout to accelerate, revs drop right down, to the point of conking out, but then drives normally as i straighten out. It's never died on me as yet, but i really want this issue fixed because it's really pissing me off!


Problems:

1) Rough idle when sitting at lights in drive (N and P seem to be alright)
2) Fuel economy, averaging 15.5L/100kms (last tank got me 310kms before fuel warning light came on)
3) Lack of power in middle rev range when wanting to overtake, there's a dull spot (around 2200 and 2600rpm) before she picks up again, almost like a flood of fuel entering the chamber.

Neways guys, i'll leave it at about that, i think that's all i can just about tell you! Any more feedback on the issue would be awesome, keep it coming.

Thanks all,
Boojakz

 

[cladiges]

i had the same problem with the fuel economy. i was getting 320km out of a tank. and really rough idle, the problem was my engine temp sensor sending the wrong info to the ECU. got it replace cost $30. now she runs like a dream

 

[Doctor Bob]

get me the code off the original memcal, there were some pinging issues with some standard vs ones.

Rob