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Brum
P Plater
65 Posts
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 Posted - 01 Aug 2006 : 9:32:08 PM
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Hey guys,
Having some trouble with fuel consumption over the last couple of months. Ok here is the details of my car, and then the fuel figures... 
Stock, '91 V6 Berlina,
140,000 ORIGINAL k's, One owner (Parents)... 
Regularly serviced, and had just been serviced at holden, and they said it was running perfectly, and that 02 sensor was fine.
Tyre pressure maintained at 36pound...
Have been driving very conservatively... Dont use extra accessories like headlights during day... (Only stereo with 6x9", no amp!)
But - the only driving i do is too school, which is 3 mins away, so the engine doesnt warm up, but i let it idle for a couple of minutes in the cold mornings! Umm... thats all i can think of, and the 02 sensor was replaced a couple of years ago, and holden said it was working fine last month...
My recent fuel figures are... (most recent - tonight)(Standard fuel)
17.88L per 100km... 
14L per 100km
17L per 100km
And 21.2L per 100km USING BP ULTIMATE!!!!!
Surely something is wrong... Please help guys...
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mouce
National Driver
1525 Posts
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Posted - 01 Aug 2006 : 10:08:08 PM
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Yeah...something is SERIOUSLY wrong with those figures. You should be getting around 14-15 when you drive the pants off it and you should be able to get it down to about 11.5 driving it normally. Being conservative, even around town, you should be able to get it to 10. At least...if it's a manual you should. If it's an auto then add an extra 1L/100km to it.
When you say it's been serviced at Holden, in my experience with my local dealership, their idea of a service of a VN is to do an oil change, and check one or two spark plugs, and that's about it. Maybe check the fluid level in the auto trans. And no...I'm not kidding. The reason behind this is that they can't help but see that a VN is a 16 year old car, and it's taking up space in their workshop, the less work they do on it the faster they can get the newer cars in there. At least...that's how it is at my local one.
Hell...they don't generally look at fault codes unless you specifically tell them that the engine light has come on.
Anyway, in short, just because Holden say that it's running perfectly doesn't mean that it really is. It just means that it runs well enough to drive out of the workshop without stalling.
ON TO THE PROBLEM:
First up, glad to see the tyre pressure is nice and high, that helps.
The constant short trips are going to be what kills you though. Three minutes? Doesn't matter how long you leave it sit and 'warm up' for...it's still not going to be running as well as it could be. My suggestion is that you throw a shot of injector cleaner in it, and a tank of either Caltex Vortex 98 or Shell Optimax in it, and find a nice open and EMPTY road somewhere (there's plenty of those in SA) and cruise for a bit, then come to a stop, and hammer it as hard as you can to get to 100kph. Do that a couple of times, just to blow the cob-webs out of the poor little motor.
The reason I didn't suggest BP Ultimate is that it's (last I heard) an E3 fuel. I'm not a fan of ethanol laced fuels.
If it's an auto: when was the last time the fluid was checked/changed? A slipping transmission will be causing it to use more fuel than it needs.
At 140,000km I wouldn't expect it to be burnt valve seats, but I would still suggest running a compression test on each cylinder, just to see that they all match up. If you've got access to a vac gauge, plumb it in and see how it reacts while you're driving and while you're at idle. http://users.bigpond.net.au/ergoff/vac1.htm
When did you first notice your fuel consumption go to poo?
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Bite off more than you can chew, and chew like hell - Peter Brock (1945-2006) |
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lolo
Fully Licenced
503 Posts
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Posted - 01 Aug 2006 : 11:29:04 PM
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| mate thats worse fuel consumption than i had when i was running on 4 cylinders...does the engine light come on....if not check the engine light lightbulb....id say to get your coil pack and DFI module checked...thats what was giving me sh1t fuel consumption....and for gods sake go to a trustworthy independant mechanic that relies on business from regular clients to make a living. |
Marcus Rogulic R.I.P (1980-2007)
"The Good Die Young" |
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Brum
P Plater
65 Posts
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Posted - 03 Aug 2006 : 9:52:06 PM
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@ Mouse...
I frequently check all the oil levels, and the trans oil is fine, but it actually has a bit more than required! As it was only replaced 3 months ago... Is that bad?
I specifically asked holden to check for the fuel, and they said there were no fault codes showing etc.
There have been no lights coming on, but i have noticed my fuel cosumption going up, ever since i changed my oil, and used Nulon 15W/40 oil? Anyone tried this?
Yeah, im the bloke whos about to try that Slick 50 fuel injector treatment, so ill give that a whirl...
Have no idea where to hookup the vacuum guage tho...
Thanks guys!
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Brum
P Plater
65 Posts
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Posted - 03 Aug 2006 : 9:54:58 PM
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@ lolo...
Hey mate, no engine lights come on, but i will get around to checking the globes!
I recently replaced my leads and plugs, properly gapped too!
But is there an easy way to check my ignition module?
Also, i have a local mechanic that i know reasonably well, and he couldnt find anything wrong with it, so he told me to take it to holden... so now im stumped... |
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lolo
Fully Licenced
503 Posts
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Posted - 03 Aug 2006 : 11:10:07 PM
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| lol now you got me stumped..... daamn what can i say...maybe try another mechanic as for the ingnition module...I dont think there is any "easy" way of checking it... tried checking the fuel lines...??? stumped I am lol |
Marcus Rogulic R.I.P (1980-2007)
"The Good Die Young" |
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mouce
National Driver
1525 Posts
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Posted - 04 Aug 2006 : 10:58:28 AM
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You can check each of the 'coils' in a bit of a rough and ready manner. Go for a bit of a drive, and pull over, pop the bonnet, and feel the coils, if one coil is hotter than the rest, it's a good sign that it's not healthy.
As for checking the DFI module (the thing under the coils), as far as I know, the only way to 'check' that is to replace it with a known one.
This really is a good puzzle isn't it? It's given me something to think about at work, thank you. :) |
Bite off more than you can chew, and chew like hell - Peter Brock (1945-2006) |
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Brum
P Plater
65 Posts
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Posted - 04 Aug 2006 : 10:47:26 PM
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Yeah, im about to try another mechanic and he's a commodore specialist... so we'll soon see!
Umm... Thanks for helping me more like it!
But im glad it gives you something to ponder...
One other option is to try a Dyno Dynamics thing? Anyone tried it? They say they can test the fuel/efi components on the dyno and simulate real driving? Has anyone tried it? I will make a new topic and post it to get more hits... Thanks guys |
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Brum
P Plater
65 Posts
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Posted - 08 Aug 2006 : 8:05:38 PM
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Good news boys, covered 200km in my car this weekend, at 110kmph and then filled up, and the fuel economy dropped to 13.4L/100km!
So it must just be the short driving i do... |
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Brum
P Plater
65 Posts
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Posted - 08 Aug 2006 : 8:13:31 PM
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| Oh, and i got the commodore specialist to check the car, he said it was running fine, but had a slight miss in one of the cyclinders, which is likely considering they havent been cleaned or replaced since new! But i am currently using the Slick 50 injector treatment, but he reckons maybe get them properly cleaned, and maybe replace my cat... Any opinions great! |
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Joogie
Fully Licenced
291 Posts
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Posted - 08 Aug 2006 : 8:37:11 PM
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| I found the solution to my apparent bad fuel usage(25L/100km) was to do with my fuel filter. It was blocked so the fuel that needed to go through it couldnt and it need to go somewhere and as the hoses wernt as tight as they need to be it came out through the hose so i was losing fuel while driving. Took me ages to find my problem but i eventually got it. |
Boost me, and double clutch me so i can get my. Loss of Traction! |
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mouce
National Driver
1525 Posts
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Posted - 08 Aug 2006 : 10:20:19 PM
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Get the injectors either ultrasonically cleaned, or replaced (if they are the original ones then the spray patterns would have gone to crap).
As for replacing the cat...if it ain't broke...you know.
It doesn't take much to take the cat off and have a bit of a look through it, if you can still see light through the honeycomb mesh inside then I wouldn't bother replacing it. The only reason you may want to replace it is if your car has been running rich, or if you've run OUT of fuel and it's backfired. Either of those will stuff the cat really quickly. |
Bite off more than you can chew, and chew like hell - Peter Brock (1945-2006) |
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Brum
P Plater
65 Posts
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Posted - 28 Aug 2006 : 3:13:01 PM
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Hey Mouce,
I finally ran through that Slick 50 injector treatment, and well, it certainly isnt worth all the friggen money!
The car idles better, but fuel economy is still pathetic...
Next, maybe a set of recondtitioned and ultrasonically cleaned injectors...
Other than that, im stumped, as my fuel economy is appalling... |
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mouce
National Driver
1525 Posts
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Posted - 28 Aug 2006 : 3:24:39 PM
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Well...at least we know not to bother with that injector cleaner. Thanks for posting up with that.
As for getting the fuel figures down a bit. Done the fuel filter? (sorry if you have, can't remember if it was you or someone else who did it recently)
Compression test all of the cylinders. Maybe one of them is way down on compression (can't see why it would throw fuel figures like it has, but it's something else to check).
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Bite off more than you can chew, and chew like hell - Peter Brock (1945-2006) |
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trizo
Forum Moderator
3091 Posts
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Posted - 28 Aug 2006 : 4:11:43 PM
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| you said you did the fuel filter?and this made it better how long after did it strt using more juice?b4 of after the injector cleaner it may of blocked the lines or filter with crap again the cleaner might b that good!!!:() |
3 can keep a secret if 2 are dead |
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Brum
P Plater
65 Posts
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Posted - 29 Aug 2006 : 10:12:20 PM
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Hey guys, sorry it took me so long to reply...
I had the fuel filter replaced last service, in april.
Should i do it again?
@ Mouse. Could it be my fuel pump? Would it be worth putting in a fuel pump from a supercharged VX? Im guessing that it would flow more?
Also, is there any difference between VN series 1 and 2 injectors?
I have a series 2, and what about VP series 1 injectors? Are they not all the same?
Last thing, is it worth putting a larger, 70mm throttle body with port matched elbow on a stock car, with low k's? Cheers mate |
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Brum
P Plater
65 Posts
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Posted - 29 Aug 2006 : 10:20:20 PM
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@ Mouse.
Had an awesome idea, you should write a manual for the Vn commodore with how-to's, mods, and maintence...
It would sure compete with Gregorys... lol
And i would definately buy one! |
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Brum
P Plater
65 Posts
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mouce
National Driver
1525 Posts
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Posted - 29 Aug 2006 : 10:53:05 PM
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The fuel filter should be good for two years or 40,000km whichever comes first. That's what the recommended service life is anyway. You shouldn't have to change it again just yet, unless you've done something crazy like a) run your tank dry so that it sucked up all the crud from the bottom or b) run an ethanol laced fuel through your car (the ethanol will dislodge any crud from the bottom of your tank and guess where it ends up?). Might actually be worth dropping your tank out and cleaning it out by hand (it's not that hard to get it out).
Fuel pumps in VN's are quite nice, they tend to be what I call a 'binary' device, either they work, or they don't, simple as that. When the fuel pump is on the way out, it tends to make quite an audible whine when the engine is running, when it does die, you can't get the engine to do anything but idle, and even then it has a hard time doing that. If you're concerned about it being either the fuel pump or the filter, get a fuel pressure gauge, or go and give a mechanic $20 and get him to test it for you. It takes all of about 2 minutes. If the pressure is low but stable, then you're filter sounds like the culprit, if it's fluctuating then I'd say it's the pump.
To the best of my knowledge there's no difference in injectors from any of the n/a V6 engines from VN S1 all the way through to VX S2. The supercharged V6 engines had slightly bigger ones (I think), but the n/a ones were all the same (as far as I know anyway).
I'm still saying that you should compression test the cylinders. It's always worth doing that every 12 months just to keep an eye on the condition of the rings and the valves.
Is it worth putting a 70mm t/b on the VN. Hell yes it is. BUT since your car is not behaving itself, let's get the sucker running properly before you go looking for a slightly more snappy throttle response. Just so you know, the larger t/b won't actually give you any more power, but it will give a slightly more lively throttle response at low throttle percentages. The matched elbow is something that is often overlooked, and will help things along. But as I said...let's get the car running properly first.
As for writing a manual on how to look after and love your VN...what do you think the last 711 posts of mine have been? LOL. There's a how-to section on here and all anyone needs to do is ask and if I can I'll write up a full how-to guide with pictures (if I can take them) on how to do whatever people want. Check it out, there's a few in there now. It's open for anyone to add a how-to guide to, so long as it hasn't already been covered, and it's not an illegal modification. I might write a book at some point, but I prefer to just answer people's questions as they come up, that way I can personalise the help a bit, plus it's damn good fun.
The metal intake pipe...for starters, I'd rather avoid aluminium, I'd rather go for Stainless, sure, it's more expensive, and it's heavier, but it's going to last way longer, and look good for longer. Heat transfer like that isn't a huge issue believe it or not, yeah the pipe will get warm, but with the speed at which the air moves through the intake pipe, even at moderate revs, it's not in there long enough to actually heat up noticeably. The metal intake pipes are used for one of two reasons either a) to go with the fully sick neons under the car bro! or b) to mount a pod filter that is not inside a box, so that it doesn't 'flop' around on the end of the plastic one. There's little to no point running a metal intake pipe if it's just going to an air box, unless it's there for cosmetic reasons.
I'm considering getting a metal one for my car, so that I can mount my pod a little more securely, but then again...what I've got works, and there's no performance gain to be had from it...so I'd say just hang on to your money. |
Bite off more than you can chew, and chew like hell - Peter Brock (1945-2006) |
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Brum
P Plater
65 Posts
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Posted - 07 Sep 2006 : 10:09:19 PM
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| Hey mouce, i kno you always say use good quality oil, and i have always used the Penrite HPR 15, but it always comes out black and gluggy, so im currently using Nulon 15w/40. It still seems a honey colour after 5 months. But i was looking at trying something else. Sine they are all normal oils, would it not be wise to use a full-synthetic oil in my car, such as the Penrite SIN 15W/40? ONly thing is its like $70. WOuld the full-synthetic be alright?? Cheers |
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mouce
National Driver
1525 Posts
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Posted - 08 Sep 2006 : 9:59:22 PM
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Full synthetic oils would be okay, but in my opinion it would be a complete waste of money in our cars. You've gotta remember that our cars were designed to run a natural oil. Since it's hard to find a good quality oil that isn't semi-synthetic most people run a semi in there. Full synth oils are the type of oils that are recommended for performance vehicles and highly stressed engines.
To me there's $35 that I don't need to spend on the SIN oils...they're damn good oils, but not much point for a VN.
As for your oil and how it comes out there's two schools of thought on it, and they are both valid (which is a bit of a downer):
1) If the oil comes out black and gluggy it may not be doing such a fantastic job lubricating things, but you know that it's cleaning crap outta there.
2) If the oil comes out all honey coloured and nice, it might be doing okay as a lube, but it might be leaving a whole lotta crap in there that should be coming out.
Ideally you want an oil that's not coming out lumpy, but it shouldn't come out clear either. If you put a few drops on a sheet of paper you should be able to see a little golden brown around the edges (ie. it shouldn't be burnt black, but it shouldn't be completely honey coloured).
If you do do something crazy like try out the Penrite SIN oil, let me know how it goes, be interesting to see what you think, |
Bite off more than you can chew, and chew like hell - Peter Brock (1945-2006) |
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