Sluggish VP V8

[Chuff]

Thanks for the reply vsuterus.

I was just telling my mate yesterday that the VP is perfect, apart from the lack of power, so I agree in that if it still went like stink, then it may never have been sold.

I too believe it is something relatively simple and hopefully cheap to fix, it's just a case of tracking it down. I have so many receipts for it from the previous 2 owners, that tracking them down would take no time at all, but I am reluctant to do this. It's no longer there problem, and I really don't want to hassle them, although I agree, it could help.

With regards to the O2 sensor, which is a 2 wire jobbie, it may have been a bad connection that pepped things up a bit, but in hindsight it did make a big difference, but I now believe that there should have been a lot more. Sadly, this just highlights how poorly it goes.

Having said all that, I will change the O2 sensor. For the sake of $80, it can't hurt.

And finally, in the previous post I detailed most of the symptoms but left one out one very important one. Throttle response. There is none. When my wife took my dad's car for a drive, her first comment was the responsiveness of his V6.

Anyway, I'll persevere. Whether I find it, or finally give up an pay someone else, it will be fixed.

CATCH!

 

[Chuff]

Update.

I changed the O2 sensor and no difference has been noticed. As I've already stated elsewhere, reading the ECU data into my laptop via the ALDL connector indicates no propblems with any of the sensors, apart from a tempremental VSS which plays up every so often.

Another sympton, which may or may not help in tracking the problem, is that the car lately tends to go great when cold, but crap when warmer after a drive. The other day I cruised for an hour or so on the open road, and WOT power was crap afterwards, whereas this morning, while still cold, I almost had it sideways (accidentally) coming home from the shops.

Don't know if anyone has experienced this lack of power when warm scenario, but I thought I would just add it, as it may trigger someone else's experience, which may be the cure I am looking for.

Thanks.

CATCH!

 

[OSL-060]

Check the alternator output under load, just suggesting it in regards to all the electrical dramas you've had. Then check the coolant temp sensor, maybe share the efi live/winaldl records of temps. Could be something as simple as overfuelling, so I'd check the thermostat too. It plays a part in controlling temps the coolant sensor reads. Maybe even try fitting a cooler thermostat straight up, cheap process and it'll be good for a slight power increase when warm.

Injectors- Have them tested

Pressure Reg- Test fuel pressure before and after yourself if your keen

Faulty ECU- Swap it with your Dads ECU (keep the V8 memcal of course) You won't hurt anything provided power is d/c throughout the process.

G'luck, this has to go down as the longest thread in JC's history

 

[Garth]

im scared

dont worry about my title, i just wanted to put that up,

yes, this is going down as the longest thread in history. and quite a nice one if that

vss well, if that is playing up your spedo will do all sorts of silly things, i.e. jump from 0 to 200kmph in 1st gear, mine did that,

as for the brake fail light, and the alternator light, there is a post within this forum where a fella had a problem, i do belive it came down to the good old bad earth drama. his was loacted behidn his instrument cluster, no earth for the cluster, it was forced to use a seperate earth, and as a result, send everthing into a spin. so check those connectors at the rear of the instrument cluster

as for slugish performance, well, i do belive it is a v8, so yeah, check that timing champ, make sure she's not retarted way to much or beyond the 10degres beyond or above top dead centre. check that fuel system, make sure fuel is getting up there, presure test fuel reg, and make sure that your throtle body isnt dirty or cloged up with some goo, check that good old fravorite part of mine the air cleaner, make sure she's all nice and clean. ensure that there are no air leakes between airbox and the throtle body its's self, make sure all hoses are tight in the breather pipe, (clamps i mean) and make sure that the butterfly isnt warped or stuck in anyway.

just another thing to think about and probably sugest this one. seing everything else has been covered, could it be posible you have got either brake lock? auto trannyslip? or even a blown head gasket? it is posible for the head gasket to cause drama's, cause it will loose compression on any givin cylinder dependiong where the brake is ofcourse, and still not give the signs of a blown head gasket. as for brakes, yeah, well they expend when hot, so you could have a caliper not retarding when released, rubbing disc's on rotor and causing brakes to sweel up? cause that could cuase the brake fail light also

auto tranny, yeah, well if your auto is slipping, (this will usualy only happen when warm) you will lose a set amount in control threwout the gearbag, i.e. lose close to 500rpm more than the usual loss amount.

alternator light, check that voltage regulator, if its not making a good contact with the brushes onto the computator it will not alow the charging to happen, as a result, the battery light will come on, you stop the motor, and it shakes, start the motor, it shakes, and it sometimes shakes a bit more out of those brushes to make just enough contact to work, so inspect those brushes/voltreg. a way to test that is to take a voltage reading of battery when car isnt running, and one when the car is running, if the voltage reading from the car running isnt bigger than the one where car isnt running, you got a charging system fault, more than likley those brushes

i hope this will help you in some way, remember, it's usualy something so simple it's not funny, also, where are ya? im in the south east queensland area, near the gold cost, more than happy go get otu there and help if needed,

cheers
garth

this is a long reply

 

[Chuff]

Garth & OSL-060,

Thanks for the replies.

Yes, 7 pages is a pretty long thread, but considering that when I started, I had a good general automotive knowledge, but didn't know a thing about EFI or Commodores, so to me, this has been absolutely invaluable, as I have learnt so much that I can confidently eliminate most possible causes.

As I've already said, and thanks to this site and others, I have been able to make an ALDL cable, down load appropriate software and analyse the data going into the ECU. All seems fine with the sensors apart from the intermittent VSS reading. This still baffles me, as it only reads incorrectly during higher RPM values (say over 4000) and when I've got it floored. I haven't tried high RPM at part throttle, but I wouldn't think that the results, whether different or not, would indicate one thing over another.

OSL-060, as I've already stated, I am convinced that the problem is not related to any sensor which can be monitored via the ECU, as I have monitored them all and can't fault them. This leads me to think that it must be something that is not sensor driven, and thus I cannot get a reading from the ECU. For this reason, I agree that the fuel pressure regulator and/or injectors could be at fault, but my question would have to be is in possible to have these components falter intermittently?

Haven't had a chance to swap the ECU with my dad's as he's caravanning (ah retirement. It's a wonderful thing!) but I will when he gets back.

Garth, I've checked all the earths under the bonnet, and they are fine. Haven't looked behind the dash, as I had a peek under there while checking fuses, and it's a wiring nightmare. Timing has been checked and is fine. Correct me if I'm wrong, but as the timing is static in its initial setting, then the lack of power & response would be consistent throughout the rev range and operating temperature of the engine if the timing were out, and this isn't the case.

I've taken the throttle body off and cleaned it. This has made no difference, and it wasn't that dirty in the first place.

Air cleaner is K&N and has been cleaned and oiled recently so no problem there and all hoses are fine.

I don't think it would be brake lock as the car has never had any problems rolling under no throttle, as if it was sufficient enough brake lock to counter the power of the car, then you would definitely notice it when coasting.

Tranny slip. Could be a possibility. The tranny does seem much firmer in its change when cold. Whether this means anything, I don't know. My mechanic said he looked into it, but I might take it to the tranny joint myself just to be sure. Another thing I noticed with the WinALDL software is the the TCC Locked value was always false, but I got the same consistent false value when reading my dad's VP as well, so either both our cars are faulty, or the software is faulty. I'm inclined to think it is the software, so unless proven otherwise, I'm assuming that the TCC is OK.

Blown head gasket. Could be, but there are no other indications of this such as water & oil mixing or pressurising of the cooling system. I don't know what else to check for a blown head gasket. To date I haven't done a compression or leak down test as I have been concentrating on electronics, but I will have to at some stage as I'm eliminating most of the electronics as the possible cause.

Alternator may be dodgy, as the light has been flashing on & off every so often. I'll have this checked out in the next few weeks.

I'm in Melbourne, so I can't show you the car, but I very much appreciate the offer.

All in all, this has been a very long thread and I have learnt heaps, and I believe I've systematically eliminated many of the possible causes. Unfortunately, I haven't actually found THE cause, but I'm a stubborn old fart, and I'll be damned if this thing is going to get the better of me.

To everyone that has had any input to this thread, thanks for everything.

The hunt continues, and I will keep you all posted.

CATCH!

 

[VQST80]

Check Your Kick Down Cable

TRY ADJUSTING YOUR KICK DOWN CABLE CHUFF
NOT TO SURE WHAT THE CORRECT PROCEDURE IS BUT WHEN I BOUGHT MY ST80 IT WAS SLUGGISH AND SLAMMIN GEARS.
mY MECHANIC MATE SET THE CABLE WITH THE TRANS IN SECOND GEAR AND NOW IT GOES LIKE IT SHOULD.
STOCK 5LTR SHOULD SMOKE V6`S ESPECIALLY AFTA 100KPH
NICE RIDE BY THA WAY.
MY MISSUS IS JELOUS!!!

 

[OSL-060]

As I've already said, and thanks to this site and others, I have been able to make an ALDL cable, down load appropriate software and analyse the data going into the ECU. All seems fine with the sensors apart from the intermittent VSS reading. This still baffles me, as it only reads incorrectly during higher RPM values (say over 4000) and when I've got it floored. I haven't tried high RPM at part throttle, but I wouldn't think that the results, whether different or not, would indicate one thing over another.

Apparently the speed sensor readings in EFI Live and some other backyard progs have a bug which contributes to inaccurate data.

OSL-060, as I've already stated, I am convinced that the problem is not related to any sensor which can be monitored via the ECU, as I have monitored them all and can't fault them. This leads me to think that it must be something that is not sensor driven, and thus I cannot get a reading from the ECU. For this reason, I agree that the fuel pressure regulator and/or injectors could be at fault, but my question would have to be is in possible to have these components falter intermittently?

No intermittently is doubtful unless your pump is to blame, As I said....test fuel pressure.

I never meant the Coolant temp sensor was to blame, more along the lines of the readings it's recieving. You're now saying that the problem is temp sensitive, maybe the thermostat is jammed one way or another.

Tested output at that Alt yet? You seem to be doing a lot of data reading and no traditional testing. Fuel Pressure should have been part of your intitial diagnosis. Fuel, spark, compression....cam turns in one piece, exhaust is expelled

People uneccessarily complicate EFI....but I tried to say that 30 posts ago

Keep us informed, can't wait to hear what this is.

 

[OSL-060]

TRY ADJUSTING YOUR KICK DOWN CABLE CHUFF
NOT TO SURE WHAT THE CORRECT PROCEDURE IS BUT WHEN I BOUGHT MY ST80 IT WAS SLUGGISH AND SLAMMIN GEARS.
mY MECHANIC MATE SET THE CABLE WITH THE TRANS IN SECOND GEAR AND NOW IT GOES LIKE IT SHOULD.
STOCK 5LTR SHOULD SMOKE V6`S ESPECIALLY AFTA 100KPH
NICE RIDE BY THA WAY.
MY MISSUS IS JELOUS!!!

That's true but surely he's tried manually shifting the old girl by now.

It's one of the better ways to milk decent shifts out of a stock TH700 behind the 5.0L. I never used to shift mine any other way.

 

[VQST80]

yeah i was suprised how much differnce the drive quailty was afta a few mil of adjustment.
is there a proper way to set kick down cables?
I hate the engine cover on the throttle body, so hard to get off when hot so i just took it off and left it in the shed.
heaps easier to work on now.

 

[OSL-060]

is there a proper way to set kick down cables?

I like mine set so it's fullly kicked down at WOT (wide open throttle), some are set up earlier but you can get nasty things like the box wanting to kick down to 3rd at 210kph. Under controlled Qld Raceway conditions of course