Terrible fuel mileage that mechanics can't fix
Submitted: Saturday, Dec 13, 2008 at 17:12
ThreadID:
64235
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3399
Replies:
7
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bucky00
Hi all
I've got a 1988 swb gq 4.2 dual fuel automatic and it only gets 3 km per litre or 33 litres per hundred, whatever you want to call it. I've lost count of the number of dino tunes I've given it and had it tuned to economy, I've had the gas system overhauled and then serviced every 5000 km, when I had the transmission serviced I had the gear changing set to more overdrive.
I've put electronic ignition on it, I've taken it to four wheel drive specialist mechanics / gas specialists to fix it so many times and when I fill up the car afterwards, they've never fixed it. Even on the highway, running premium unleaded, cruise control, 100 km/h, narrow 30 inch road tyres, 45 psi, no passengers or weight or roof rack, not even a bull bar, cooler weather, no hills, it only gets 3 km per litre / 33 litres per hundred, no better than what it gets around town either, other people with the same cars with everything I just said get at least 5 km per litre / 20 litres per hundred. I had a compression test done on the engine and it's in fairly good condition, it's got new bearings and diffs and an overhauled transmission and the car serviced every 5000 km, it doesn't matter who drives it either. Has anyone got any suggestions?
Reply By: Member - Footloose - Saturday, Dec 13, 2008 at 17:29
Saturday, Dec 13, 2008 at 17:29
Liftum foot ?
Fuel leak ?
Holly carb needs turfing ? :))
AnswerID:
339523
Follow Up By: bucky00 - Saturday, Dec 13, 2008 at 17:47
Saturday, Dec 13, 2008 at 17:47
It doesn't matter how soft I am on the right foot it gets bleep mileage and it's funny, it doesn't get better mileage driving softly on the right foot than it does driving medium and but it gets worser mileage driving hard. I've had it checked for fuel leaks twice and it's fine and the carby's had an overhaul twice.
FollowupID:
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Follow Up By: Pat Malone - Saturday, Dec 13, 2008 at 18:03
Saturday, Dec 13, 2008 at 18:03
holly carb ????
FollowupID:
607038
Follow Up By: bucky00 - Saturday, Dec 13, 2008 at 18:19
Saturday, Dec 13, 2008 at 18:19
It's a standard Nissan one and in case you're all wondering I'm pretty easy on the right foot, it doesn't matter who's driving it gets the same mileage and even when I'm real soft on the right foot and getting heaps overtaking me it gets the same bleep mileage and I live in the country to and I live on a 100 km/h highway.
FollowupID:
607042
Follow Up By: Member - Footloose - Saturday, Dec 13, 2008 at 22:19
Saturday, Dec 13, 2008 at 22:19
PM. Doesn't anyone know the symbol for smilies ? It indicates that I'm not being entirely serious.
I drove an old Landcruiser FJ55V petrol for a few years. It had a Holly carb and extractors, and was way too quick for the brakes and
suspension. It also had woeful economy, however the only time it returned those sort of figures was on a
Simpson Desert crossing in the early 80's.
FollowupID:
607100
Follow Up By: Member - Royce- Saturday, Dec 13, 2008 at 23:10
Saturday, Dec 13, 2008 at 23:10
Release the handbrake!
FollowupID:
607107
Reply By: Member - Phil G (SA) - Saturday, Dec 13, 2008 at 18:39
Saturday, Dec 13, 2008 at 18:39
How accurate is your odometer? Worth checking against a GPS, if you haven't already done so. My recollection is that those old Nissans overread a fair bit, especially with 30" tyres.
AnswerID:
339538
Follow Up By: bucky00 - Saturday, Dec 13, 2008 at 18:41
Saturday, Dec 13, 2008 at 18:41
I use the tripmetre on my GPS, you can't get any more accurate than that and I fill out a log book every time I fill up and calculate my mileage with a calculator.
FollowupID:
607045
Follow Up By: bucky00 - Saturday, Dec 13, 2008 at 18:42
Saturday, Dec 13, 2008 at 18:42
I use the tripmetre on my GPS, you can't get any more accurate than that and I fill out a log book every time I fill up and calculate my mileage with a calculator.
FollowupID:
607047
Follow Up By: Member - Phil G (SA) - Saturday, Dec 13, 2008 at 18:50
Saturday, Dec 13, 2008 at 18:50
Gday Bucky00,
Geeze the server is giving us a hard time tonight!
Can't argue with a GPS! Thats what I use too. Out of interest, how much is the speedo out?
Cheers
Phil
FollowupID:
607050
Follow Up By: bucky00 - Saturday, Dec 13, 2008 at 18:55
Saturday, Dec 13, 2008 at 18:55
The speedo says about 10% faster than I'm really going and the standard trip metre says about 4% more than I've really gone, it's funny how the speedo can be of different accuracy to the trip metre.
FollowupID:
607054
Reply By: Flywest - Saturday, Dec 13, 2008 at 19:38
Saturday, Dec 13, 2008 at 19:38
Ummm
Maybe you have it stuck in low range everywhere you go?
Really it sounds a lot to me like your torque converter is slipping badly for that sort of mileage!
As an example - I get 5 KM/ Liter of diesel and auto gas combined, in a 7.3 liter v 8 intercooled diesel F 250 hauling 4.5 tonnes of boat at 100 km/hr on cruise control. (Bout 9 tonnes rolling mass all up).
You can have the torque converter replaced and even get one with an electronic lock up feature if you want, so that your connected 100% to the drive shaft at 1:1 ratio and not getting any slippage there.
Sounds like you have a bad slipping auto trans to me and thats usually the torque converter but not always - it could also be the wet clutch pack if it is worn out.
Go see an auto tranny man - whoever did your dyno tuning should have picked up the transmission slip on their read out graphs, at the rear
wheels.
Good luck with it.
Cheers
AnswerID:
339548
Reply By: Member - Shane D (QLD) - Saturday, Dec 13, 2008 at 22:07
Saturday, Dec 13, 2008 at 22:07
My guess is also the Torque convertor or Tranny.
If everything is set right at the motor, problem maybe further back.
I had a MWB petrol/gas Cruiser( 4.2 manual) and it consistantly got 25l/100k on gas JUST city driving, I wasn't nursing it either.
Shane
AnswerID:
339575
Reply By: ross - Saturday, Dec 13, 2008 at 23:40
Saturday, Dec 13, 2008 at 23:40
Has anyone does a breathyliser on the exhaust gasses?
If an engine is using about double its nomal fuel consumption ,surely the exhaust would smell pretty rich
At 33/100 ,you would think you could catch the fuel in a bucket at the exhaust pipe.
AnswerID:
339584
Follow Up By: bucky00 - Sunday, Dec 14, 2008 at 08:49
Sunday, Dec 14, 2008 at 08:49
No I don't think they have or at least they haven't told me but I'll look into it, thanks
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607136
Reply By: GerryP - Sunday, Dec 14, 2008 at 12:05
Sunday, Dec 14, 2008 at 12:05
Hi Bucky00,
Used to have an 89 GQ on petrol/gas but was a manual. Never managed better than 26 l/100 and regularly went up to 30 towing or off roading. Mind you,
mine was pretty loaded up all of the time. Like you, tried everything but failed to fix it. Becuase of this, as
well as the difficulty in getting gas, or even petrol in remote
places, ended up swapping to a diesel.
Would be very interested to know if you find a fix. The annoying bit was that there were 2 or 3 others in our 4wd club with petrol GQ's all getting much better economy - never did find out why.
Don't wish to sound negative though mate - really hope you come up with an answer as they are basically a very good, tough truck.
Cheers
Gerry
AnswerID:
339652
Reply By: Tippa - Sunday, Dec 14, 2008 at 18:30
Sunday, Dec 14, 2008 at 18:30
I wouldnt be looking at the torque converter as they are a mechanical/hydraulic component which cant wear or "slip" more than normal unless it has internal rotor or stator vane damage- which i would highly doubt.
How
well does she go? Is it down on power do you think?
I'm thinking, if its been tuned and tuned again, thats not the problem. So maybe its something like cam timing.
I dont know these engines, but if they are overhead cam, maybe the belt has slipped or been put on one tooth out when last replaced, or if its a chain then it may have stretched/worn.
Just an idea...
Also if its idling rough, check for vacuum leaks.
Good luck!
AnswerID:
339723
Follow Up By: Tippa - Sunday, Dec 14, 2008 at 18:33
Sunday, Dec 14, 2008 at 18:33
Oh and one last thing... your exhaust may be restrictive. Check all mufflers for broken and freed baffles (tap case with a hammer and listen for them rattling loose inside) or a melted down catalytic converter if it has one fitted (actually quite likely... remove and look thru the core).
Cheers!
FollowupID:
607243