Sluggish VP V8

[Chuff]

VQST80 & OSL-060,

Thanks. I have tried manual shifting it and it doesn't make any difference. The car itself has no problem downshifting, as when I boot it, if it needs to go down a gear or 2, it does.

OSL-060, as I've already said, I haven't had a chance to test the fuel pressure or regulator as yet. I do not have the necessary equipment to test EFI fuel pressure, and I'm undecided as to whether to buy the equipment, or get a mechanic to test it, as if I go with the mechanic, then I want to drive it and learn as much as possible so I can direct him in the right direction, rather than having him go off on a tangent checking things I have already checked at his standard $$$$ per hour. The car is the wife's car, and as such, I only get to drive it on the weekend, and this is when I can analyse what it's doing.

With regards to the temperature, what I was highlighting was that generally the car goes crisp and hard when cold, and the problem of lack of power and response seems to be occurring only when the temperature of the engine has reached normal operating temperature, and then intermittently it seems to loose power. Once normal operating temperature is reached, this is where it stays. In that regard, the car is not overheating, and the temperature gauge indicates a perfect temperature, as does the data gather from the ECU

So that's it. I will get the fuel pressure checked once I learn a bit more of the car's characteristics. I do appreciate all the input given by everyone, and I am trying to relay as accurately as possible the behaviour of the old girl, but obviously the only way to really understand what's going on is to drive it. What makes things worse is that everything I have stated can be true at any given point, and false at any other given point. That's the frustrating thing about it. It's not consistent.

So I persevere, and I will keep you all up to date.

CATCH!

 

[vnstu]

any luck yet?

just a couple of thoughts...

you noticed a change in performance when master resetting the ECU and playing with the o2 sensor. have you tried that again, and did it have any impact?

one tip my mechanic of a father gave me, reset the computer, and basically flog the crap out of the car for a bit. the computer will re-calibrate itself, optimised for performance. maybe resetting the computer while the engine is warm? i would suggest a second opinion on this, as my knowledge in this is sketchy, my VN is my first EFI, and i dont know if it has to be calibrated from a cold start.

but from what i've seen in these posts i dont think it's the computer, unless there's a matching issue with your engine. maybe throw a stock chip in, see if there's a change, and at the end of the day you'll have a spare on the shelf or you can flog it on ebay, and it's another factor cancelled from the equation.

anyway, the point i wanted to make, in my dayjob as an electronic engineer, if you get any variables changing with temperature, as your engine performance seems to be, it's usually because of a changing resistance value. increased temperature causes increased electrical resistance in metal components (ie resistors, inductors etc) and decreased resistance in semi-conductors (transistors, diodes etc). and is this weather related as well? does it run significantly better late at night than on a stinking hot day even when warm (ie air temperature related) or is it purely related to engine temperature? if a critial wire or component is hotter than it should be, it will have a higher resistance, which will change the voltage, which mayl impact on engine performance.

my 2 cents are free
stu

 

[Slooth]

anyway, the point i wanted to make, in my dayjob as an electronic engineer...

Electronic engineer! You might come in handy somewhere down the track!

 

[Chuff]

Update.

I haven't touched the car lately, as I've been too busy doing holiday stuff! What I have done is purchased a genuine Holden VP & VQ Series II Vol 4 manual for the 5 litre EFI engine, and I have been reading up on how it all works.

The information in this manual, describing not only how absolutely everything EFI works, but also the in depth diagnostics are proving invaluable. This book is an must for anyone wanting to understand, in detail, how all this stuff works. It is without doubt the best $50 I have ever spent on any auto related book, as the EFI information is complete, and nothing has been left out.

I have read most of it, but will need to read it again in order to fully absorb the information contained within, but it has already highlighted some interesting points which I will be investigating further once I have some time.

I'll let you know how it all goes.

CATCH!

 

[rachv8ss]

I know this post is like 10 years old so i hope you reply.. after reading through 8 pages theres no update on if issue was found.. its exactly the same problem we are having at the moment with a vn ss... please tell me all these years later you ended up finding the problem and can help with some info so we can fix our vn..
We have replaced all plugs leads.. had timing reset, flushed fuel tank and lines.. new internal and external fuel pumps and filter.. cleaned out injectors.. but it just has no guts at all, its a snail !

 

[EYY]

It's 25 years old now, probably due for a rebuild.

They're not the quickest things around anyway, pretty slow actually in standard form.

 

[Circlotron]

its exactly the same problem we are having at the moment with a vn ss... please tell me all these years later you ended up finding the problem and can help with some info so we can fix our vn..

Maybe you are just the latest person to own Chuff's car...

 

[rachv8ss]

Hahaha reading his post i was actually thinking that except his was vp

 

[Jxfwsf]

Rebuild and stroke it.....

 

[Chuff]

Maybe you are just the latest person to own Chuff's car...

Nope. I still got it, and I ain't selling it. :smoking:

The Calais is now hidden away awaiting an engine rebuild & club reg in 2018. Since putting it into storage 3 years ago I have not seen many VP Calais getting around, and none are even close to the condition of mine, so it's a keeper, especially with all the bits 'n' pieces it's got on it.

Sluggishness was probably as a result of a tired motor. Previous owner must have driven it hard, and with all the goodies on it, I don't blame him. In the end I ended up burning my own chips for the ECU and got some good gains over the Chip-Torque crap that the previous owner installed. This, and changing the diff from a 3.08 open to 3.89 LSD made all the difference, and that's how the wife drove it till we parked it.

Chuff