Gas milage
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Dreamcar86
Active Member
- Joined
- Apr 13, 2006
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You have not given any information. How many miles on engine, injectors, chip, etc. The more information the easier it is to find the problem.
The engine has about 20,000 since the last owner rebuilt it.The car also has 36lb blue tops, hi pressure regulator,wabaro 340 with hot wire,210 205 cam, J carter chip.One other thing is the fuel gauge don,t work and I just caculate the mile and the gallons I put in the car.Last time I filled up the tank and got 125 miles and the car ran out of fuel.Thanks for the help.
Scanmaster 2.1 reading are 02 078,725 af05 L8 37 int 128 bl 139 clt 168 ats 112 r 800 900 tps 42 iac 00 175 cc 116.The last owner told me he got 23 mpg I wish.
Something is really wrong, I can still get over 200 miles per tank, haven't checked freeway mileage lately (Just got GN out of parents garage for the first time in over a year) but even with the mototron injectors I figure I'd get at least 23mpg.
Has the mileage always been this bad? Did you make any changes lately?
Has the mileage always been this bad? Did you make any changes lately?
No I hade the car since say last november And I park it to about april got it painted and after the paint I put it on the roadand didn't put 500 mile on the car yet
No fuel leak and it has the stock exhaust cat dp
Well we are close to the same setup, I have stock exhuast DP back, I get 21-23mpg highway, 15-20 city/highway without the TC locking (trans problem) Worst was 15mpg and I was doing a bunch of testing/playing.
Pull the plugs and have a look at them.
Pull the plugs and have a look at them.
I only get between 12 and 14 mpg but the car is not my daily driver and Im always in boost when I do drive it. I have drove it easy before though and I dont see a chance in hell of getting anything close to 23 mpg. (I dont think they even got 23 bone stock brand new?) I do have a lot of mods so who knows but all these people with mods getting 23mpg just seems a little fishy to me. Just because its a 6 cyl doesnt mean it will get great mileage.
ttypewe4jim
pa turbo buick racing
- Joined
- Dec 1, 2002
- Messages
- 1,808
Last time I had my car out I had a te61 turbo, heads, cam and 83s and it got around 22mpg
justabuickv6
Member
- Joined
- Nov 4, 2003
- Messages
- 1,037
I get 20mpg with mixed driving. I get 23 on the highway. Now, if I get in the boost a lot, it will be around 12-15 with mixed driving.
Long block is stock and the car is tuned properly.
PT52, 60lbs injectors, 3600 9x11 lockup, alky chip.
Long block is stock and the car is tuned properly.
PT52, 60lbs injectors, 3600 9x11 lockup, alky chip.
- Joined
- May 9, 2002
- Messages
- 2,576
Your IAC adjustment is way out....The bushings in your throttle body may be worn out. Look Here, under 'Basics' to learn how to set the IAC adjustment. You'll need a scan tool. 
You may want to have Jay Carter update your chip with a lean cruise.
You may want to have Jay Carter update your chip with a lean cruise.
87TTypeKid
New Member
- Joined
- Jan 23, 2006
- Messages
- 39
Actually, now that someone brought this up-
In my car, I routinely get only 15-18 no matter where I am, 18 being the best with mostly highway driving. Now, the facts about my car-
162000 miles
Mototron 60lb/hr (trimmed duty cycle)
Stock turbo (dead seals..leaks oil under heavy boost)
Hooker 2.5" cat back
TurboTweak 93 octane chip (incorrect boost- set for 17, I only run 12...no controller yet)
Passenger side exhaust manifold either has a blown gasket or something...bad exhaust/fuel odor under boost, almost instant after w.o.t. (no visible fuel leaks in engine compartment)
And I can smell gas on the drivers side when I walk up to the car sometimes...fuel feed and return lines are solid...havent checked the vapor line yet.
I haven't checked my readings since I got my engine back together...but before, all readings were fine on the scanmaster, except knock (due to 18 psi on stock chip..thank you, vacuum leaks..haha).
I will admit there's so much oil in the intake system that its plugging up the IAC from time to time...oil leaks from the bolts that hold it to the TB
The mileage was ****ty back in the day when the car was back on the road after 2 years of sitting..I was only getting maybe 13 mpg on a good day.
As far as other things go, the MAF is fine, 02 is fine, and I havent checked the TPS output yet...
Best mileage on a single tank? 280-290... I just feel like with the driving I do Im at the pump every couple of days.
Insight please! Sorry for stealing the topic- I was equally as curious about my own situation.
Thanks
In my car, I routinely get only 15-18 no matter where I am, 18 being the best with mostly highway driving. Now, the facts about my car-
162000 miles
Mototron 60lb/hr (trimmed duty cycle)
Stock turbo (dead seals..leaks oil under heavy boost)
Hooker 2.5" cat back
TurboTweak 93 octane chip (incorrect boost- set for 17, I only run 12...no controller yet)
Passenger side exhaust manifold either has a blown gasket or something...bad exhaust/fuel odor under boost, almost instant after w.o.t. (no visible fuel leaks in engine compartment)
And I can smell gas on the drivers side when I walk up to the car sometimes...fuel feed and return lines are solid...havent checked the vapor line yet.
I haven't checked my readings since I got my engine back together...but before, all readings were fine on the scanmaster, except knock (due to 18 psi on stock chip..thank you, vacuum leaks..haha).
I will admit there's so much oil in the intake system that its plugging up the IAC from time to time...oil leaks from the bolts that hold it to the TB
The mileage was ****ty back in the day when the car was back on the road after 2 years of sitting..I was only getting maybe 13 mpg on a good day.
As far as other things go, the MAF is fine, 02 is fine, and I havent checked the TPS output yet...
Best mileage on a single tank? 280-290... I just feel like with the driving I do Im at the pump every couple of days.
Insight please! Sorry for stealing the topic- I was equally as curious about my own situation.
Thanks
Do a leakdown test on the cylinders and verify that the injectors are not leaking since you smell gas. What are your cruising blm numbers? Be sure there are no exhaust leaks before the O2 sensor. Even with the non lockup and a 212-212 i get 20 mpg on the highway.
Well, last thanksgiving, I was getting almost 25 mpg on the highway - I currently am too trying to diagnose my lowered economy - I'm down to 20 w/ a fresh 02 and fuel filter.
Theres a million things that can cause it. When I first got my car, it ran like total crap and I got 8mpg. I wrote a huge thread on here about it a couple years ago. Do a search with my user name and the words gas mileage and you'll find it. What are your BLM's? My engine had alot of vacuum leaks. It had a couple torn injector o-rings making it real bad. My vacuum at idle was 12inches...real low. Whats yours? My plugs were all cracked, causing misfires, I ohmed my plug wires and one was really messed up. I replaced all that. I got a new IAC and set it, as well as the TPS. I changed my intake manifold gaskets. My PCV was working ok, but sucking alot of oil, I relocated it with a catchcan. Do a search on "boost bypass pics" and you'll see what I did. I replaced the injectors with MSD 50's, and replaced my MAF with an LS1 MAF, and added an LS1 MAf Translator and an extender chip. I added a fuel pressure guage cause it didnt have one. My fuel pressure was 50 with the line off
. Its at 38 right now. I checked everywhere for leaks. There werent any. My charcoal canister solenoid was sticking. I used a power supply at work to actuate it and blow it out, while spraying it inside with penetrant. That stopped the sticking...had nothing to do with mileage in my case. My EGR wasnt working that great. I eventually just eliminated it all together since the extender chip shuts it off. I replaced cracked hoses and used hose clamps wherever possible. This all brought my vacuum up to about 18-19 at idle. My mileage went up to about 16mpg. Now keep in mind I had a non lock Art Carr torque converter with a really hgih stall speed, so it slipped alot...plus theres no TCC lockup to bring rpm's down. I also had 4.56 gears in it that some idiot threw in. Seems that without a doubt, those gears and the TC would suck up gas like crazy. But I replaced the rear end with stock gears (original rear was a 7.5" rear..more brilliant work by the old owner). This brought my rpm's way down....but my mileage didnt improve believe it or not. Then I replaced the TC with a stock D5. My mileage didnt improve. Turned out I had a cracked drivers side header. i replaced it and my mileage improved about 1mpg..big deal. I was thinking my exhaust was plugged. A way to check it, is to rev the rpm's up in park and watch vacuum. If vacuum drops alot when you bring the rpms up and hold them, the exhaust is clogged...well, severely clogged. My vacuum didnt drop so it was fine..but replacing the exhaust may tell another story. I also replaced the cam sensor cause it was bad and adjusted it. I also adjusted the crank sensor, cause it was completely loose and getting knocked around. I replaced the ignition module. I replaced all the hoses for the IC with new clamps. New O2 sensor. My brakes were dragging, including the parking brake, so I loosened them all up. I upped my tire pressure to 40psi..this helped a bit. I checked my compression and it was ok. Ive done even more things, but my mileage has never gotten better than 18.7. usually it gets around 17 depending how I drive. I actually saw a little improvement in mileage by cutting off the big scoop to the IC..not all of it but most of it. I think the majority of gas mileage issues are cause by a poor tune, caused by vacuum leaks, bad or maladjusted sensors, and bad components like fuel injectors and ignition system parts. Misfires and dragging brakes will suck up gas like nothing else..with the exception of a clogged exhaust. You really need to replace all of that.
. Its at 38 right now. I checked everywhere for leaks. There werent any. My charcoal canister solenoid was sticking. I used a power supply at work to actuate it and blow it out, while spraying it inside with penetrant. That stopped the sticking...had nothing to do with mileage in my case. My EGR wasnt working that great. I eventually just eliminated it all together since the extender chip shuts it off. I replaced cracked hoses and used hose clamps wherever possible. This all brought my vacuum up to about 18-19 at idle. My mileage went up to about 16mpg. Now keep in mind I had a non lock Art Carr torque converter with a really hgih stall speed, so it slipped alot...plus theres no TCC lockup to bring rpm's down. I also had 4.56 gears in it that some idiot threw in. Seems that without a doubt, those gears and the TC would suck up gas like crazy. But I replaced the rear end with stock gears (original rear was a 7.5" rear..more brilliant work by the old owner). This brought my rpm's way down....but my mileage didnt improve believe it or not. Then I replaced the TC with a stock D5. My mileage didnt improve. Turned out I had a cracked drivers side header. i replaced it and my mileage improved about 1mpg..big deal. I was thinking my exhaust was plugged. A way to check it, is to rev the rpm's up in park and watch vacuum. If vacuum drops alot when you bring the rpms up and hold them, the exhaust is clogged...well, severely clogged. My vacuum didnt drop so it was fine..but replacing the exhaust may tell another story. I also replaced the cam sensor cause it was bad and adjusted it. I also adjusted the crank sensor, cause it was completely loose and getting knocked around. I replaced the ignition module. I replaced all the hoses for the IC with new clamps. New O2 sensor. My brakes were dragging, including the parking brake, so I loosened them all up. I upped my tire pressure to 40psi..this helped a bit. I checked my compression and it was ok. Ive done even more things, but my mileage has never gotten better than 18.7. usually it gets around 17 depending how I drive. I actually saw a little improvement in mileage by cutting off the big scoop to the IC..not all of it but most of it. I think the majority of gas mileage issues are cause by a poor tune, caused by vacuum leaks, bad or maladjusted sensors, and bad components like fuel injectors and ignition system parts. Misfires and dragging brakes will suck up gas like nothing else..with the exception of a clogged exhaust. You really need to replace all of that.A Long Shot...
Related to poor milage, my 170K mile relatively stock GN was getting very poor mileage. This was a gradual decrease in economy over time. I used to get 30 MPG on 95% highway driving, and 22-26 with mixed.
Eventually (100K miles later) , I was getting 12 MPG with 160 miles per tank, and I quit tracking it and started driving it less thinking my engine was just worn out. Then last year, at smog check time, it would not pass no matter what tuneup I threw at it. After failing 2X, I gave it one more shot and reduced the fuel pressure, or at least, attempted to. I hit a wall around 35 PSI. I could not adjust it lower?!?!
After a lot of head scratching, I determined that coupled with a Walbro high volume fuel pump, the fuel return line was too restrictive, resulting in high rail pressures at idle, 15, and 25 MPH tests. The BL numbers during these tests were in the low 90's.
My "Quick Fix" to get it to pass was to swap in an old low volume fuel pump, lower the line-off pressure, which reduced my high HC numbers to a point that it passed. I never drove it with this setup long enough to get MPG numbers, but the BL numbers were higher, around 105. Still rich, but enough to get it through and registered.
I have since replaced MOST of the return line, including the length up and into the tank with a mix of AN hose and aluminum 3/8 line, and put the good pump back in and returned the FPR adjustment to 43 PSI line off. I am now getting an average of 19 MPG, BL numbers much closer to 118. The one part of the line I have not replaced is the steel piece that runs from the connection near the Pwr Steering gear to the FPR. I figure this part still has some restrictions, but the replacement StSt Hard line I received was so poorly bent, I ended up putting the old one back in.
I still feel I have some restrictions in the 1 line I did not replace, resulting in some erratic BL numbers. For the most part, they are fine. But the intermittant stumble, lean out and over-rich conditions I encounter at various points in my daily 80 mile commute still occure from time to time. My increased mileage confirms this was a part of the problem.
One other thing worth mentioning: I did get an additional 2 MPG increase by fixing 1 vacuum line leak, so before going all out and replacing fuel components, I would make sure all vacuum ports and lines are checked! Some reduction in economy is due to the age/miles on not only the engine, but the car itself. Engines can be rebuilt, but we also need to consider the items that we rarely think about, like the fuel and vacuum lines we tend to "Assume" are OK! (My cracked vac line was inside some black plastic conduit and was overlooked for quite some time!)
Hope this helps!
Related to poor milage, my 170K mile relatively stock GN was getting very poor mileage. This was a gradual decrease in economy over time. I used to get 30 MPG on 95% highway driving, and 22-26 with mixed.
Eventually (100K miles later) , I was getting 12 MPG with 160 miles per tank, and I quit tracking it and started driving it less thinking my engine was just worn out. Then last year, at smog check time, it would not pass no matter what tuneup I threw at it. After failing 2X, I gave it one more shot and reduced the fuel pressure, or at least, attempted to. I hit a wall around 35 PSI. I could not adjust it lower?!?!
After a lot of head scratching, I determined that coupled with a Walbro high volume fuel pump, the fuel return line was too restrictive, resulting in high rail pressures at idle, 15, and 25 MPH tests. The BL numbers during these tests were in the low 90's.
My "Quick Fix" to get it to pass was to swap in an old low volume fuel pump, lower the line-off pressure, which reduced my high HC numbers to a point that it passed. I never drove it with this setup long enough to get MPG numbers, but the BL numbers were higher, around 105. Still rich, but enough to get it through and registered.
I have since replaced MOST of the return line, including the length up and into the tank with a mix of AN hose and aluminum 3/8 line, and put the good pump back in and returned the FPR adjustment to 43 PSI line off. I am now getting an average of 19 MPG, BL numbers much closer to 118. The one part of the line I have not replaced is the steel piece that runs from the connection near the Pwr Steering gear to the FPR. I figure this part still has some restrictions, but the replacement StSt Hard line I received was so poorly bent, I ended up putting the old one back in.
I still feel I have some restrictions in the 1 line I did not replace, resulting in some erratic BL numbers. For the most part, they are fine. But the intermittant stumble, lean out and over-rich conditions I encounter at various points in my daily 80 mile commute still occure from time to time. My increased mileage confirms this was a part of the problem.
One other thing worth mentioning: I did get an additional 2 MPG increase by fixing 1 vacuum line leak, so before going all out and replacing fuel components, I would make sure all vacuum ports and lines are checked! Some reduction in economy is due to the age/miles on not only the engine, but the car itself. Engines can be rebuilt, but we also need to consider the items that we rarely think about, like the fuel and vacuum lines we tend to "Assume" are OK! (My cracked vac line was inside some black plastic conduit and was overlooked for quite some time!)
Hope this helps!
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