Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.

New Posts Contact us

Just Commodores Forum Community

It takes just a moment to join our fantastic community

Register

runs rough runs smooth runs rough runs smooth

BobbyWatson

New Member
Joined
May 10, 2009
Messages
4
Reaction score
0
Points
0
Members Ride
VP Executive
The Car
  • 1993 Holden Commodore Executive Wagon
  • VP Series
  • V6 engine (says 3800 on top)
  • Air conditioning, automatic transmission, no modifications, very factory model car.

The Symptoms
  • The engine runs smooth most days.
  • It runs rough other days.
  • Temperature doesn't seem to be a factor - it can run smooth or rough at any time.
  • Never a problem to get it started.
  • Can be rough from the get-go, or can get rough while driving... even on the express way.
  • Revving the engine can often clear the problem, but sometimes not. It can backfire through the intake when revving.
  • I cannot reproduce the problem deliberately. I can start it and get one reaction, shut it down and restart it and get the opposite.
  • There seems to be no consistent or predictable pattern.

Two notes. (1) I have not worked on a car for a few years, so I'm out of practice. (2) A few months ago was the first time I saw a Holden in my life, so I'm not familar with the car or its jargon - aka go easy on me with the abbreviations, thanks.

Two more notes. Plugs and wires look good. Computer fault codes come up empty.

I thought this might be a common problem with the model but after reading for an hour or so I haven't come up with an answer yet. Any ideas? Thank you.
 

delcowizzid

on holiday
Joined
Jul 8, 2008
Messages
6,993
Reaction score
434
Points
83
Location
NZ
Members Ride
в∞ѕтεכ √&
do you know anyone with the same model ide borrow there engine computer and try it for a few hours and see if it still does it.or you need to start replaceing stuff to find the issue really new fuel filter etc random sensors and stuff.if you have access to a laptop they can tell yyou a lot more than just the error codes you can see if its a sensor issue
 

BobbyWatson

New Member
Joined
May 10, 2009
Messages
4
Reaction score
0
Points
0
Members Ride
VP Executive
> do you know anyone with the same model

No. "A few months ago was the first time I saw a Holden in my life" - I'm not exactly widely connected here yet.


> ide borrow there engine computer and try it for a few hours

I'd need a how-to


> or you need to start replaceing stuff

Hit or miss, trial and error, is what I'm trying to avoid.


> if you have access to a laptop they can tell you a lot

I have a laptop. How can this help?


Thanks for the input.
 

delcowizzid

on holiday
Joined
Jul 8, 2008
Messages
6,993
Reaction score
434
Points
83
Location
NZ
Members Ride
в∞ѕтεכ √&
if you make an ALDL cable which is pretty easy ill post a link to a schematic and get a copy of WINALDL free off the net you can monitor the sensors in realtime and see issues like the coolant sensor suddenly going cold is a good one normally makes the car run rough as and comes and goes this is a regular issue and is the ecu on its way out.
 

crazybiker

Member
Joined
Sep 9, 2008
Messages
703
Reaction score
3
Points
18
Location
Sydney NSW
Members Ride
VR Commodore V6
I'm willing to bet it's the ECU (Engines computer) that's shot itself.

That sounds like the exact kinda problems I was having with mine. Tried everything, and then went the ECU and it solved it.

A second hand one from the wrecker should cost you $30 or so
 

BobbyWatson

New Member
Joined
May 10, 2009
Messages
4
Reaction score
0
Points
0
Members Ride
VP Executive
I found a link on https://forums.justcommodores.com.au/threads/how-make-diagnostic-cable-your-vn-vp-commodore.5723 which should help, and one too https://forums.justcommodores.com.au/threads/change-coolant-temp-sensor-v8.86026 although it's for a v8 it still gives a hint of what I should be looking for. I found offsite links to many ALDL diagnostic programs but anything commodore-specific is much appreciated. I also found people selling ALDL cables but prices range from moderately expensive to very expensive.

However, I didn't find a link for changing the ECU. delcowizzid, since your first suggestion was to test the ECU with a known good one, it might make good sense to follow that up... the caveat being that used ones may not necessarily be good out of the box - crazybiker, that's a good suggestion... I'll look for what wreckers I can find around here.
 

delcowizzid

on holiday
Joined
Jul 8, 2008
Messages
6,993
Reaction score
434
Points
83
Location
NZ
Members Ride
в∞ѕтεכ √&
WINALDL is the easiest VN-VP software free on the net. to build a cable do it like this 2 10k resistors and a 2n2222a transistor you will need a 3rd 10k resistor as well to put the ecu into diagnostic mode.
 

Attachments

MickT

New Member
Joined
May 10, 2009
Messages
57
Reaction score
0
Points
0
Members Ride
VY SS
Let us know how you go with it. My car is doing the same thing but not backfiring.
 

goldvn05

New Member
Joined
Jan 22, 2006
Messages
34
Reaction score
0
Points
0
Location
Sydney
Members Ride
Calais V
i also would be keen to find out from you guys, how you resolved it, as im also havign the seme symptoms.

eg.
- intermitent, rough idle and rough drive.
- does rough on both hot days and cool days., then comes good on other days.
- on other thing i noticed, was increased vapour from the exhaust, when it does run rough (as if it was a winter day start up), but it was a normal 20-25 degree day.


lookig forwrd to hear back from you all how you resolved it, thanks
 
Top