Poor MPG

[TLI]

My Buick is now my DD so I have really been watching the mpg close. The best I can get is about 13 city and highway (probably a little more highway than city). I keep hearing people getting 15 or better and I have really tried to watch my driving and not get into any boost and still don't get anywhere close to that. Does anybody have any ideas?

1987 Buick
60# injectors (fp @43)
TT Chip
PTC lock up converter
63 turbo (THDP, Magnaflows, full 2.5" exhaust)
Ported factory heads, intake, cam, etc.

I'm at a loss for answers.

 

[Beamer]

Something is without a doubt wrong. I drove mine on a short trip a while back on the highway and got 22MPG with it. 88 miles and 3.96 gallons to fill back up. You can see my combo in my sig.

How is your wires and plugs? Have you looked at the condition of the plugs when you removed them? If they look black. Do you have a wide band to use for tuning? How about a scanmaster to monitor readings?

Mike

 

[bison]

What is the block learn at while cruising?

 

[I8AV8]

Have you check you rpms? Count the shift and see if you are going into 4th. If you are in 3rd your rmp should be high. If you have a non-lockup convert it will make a difference. I have not check my in town mileage, but my highway is around 24-25 mpg at 70 mph and my rpm is around 2400. I have a vigilante non-lockup converter and 70 lbs injectors. Have you had a compression test? You may have some bad valves.

 

[TLI]

I just replaced my plugs with E3 the ones that were in looked clean, just a little worn out. My wires are Magnacore that I have had for a while. The BLM's are around 128 to 130. The cross counts are changing fairly quickly and I have it in OD on the highway. At 70 the RPMs are around 2200. I don't know if the valves are bad or not, but it runs well when you get on it.

 

[TLI]

By the way I do not have a WB. I have a Direct Scan and tune that way.

Thanks for the help so far.

 

[LS954]

same here ive been averaging about the same in the city since my rebuild. Ill be driving it down to florida tonight and will see how much im getting on the hwy. Prior to my build the highest i seen on the hwy was about 19. By the way my BLM while cruising is on the low side of the 128 mark(about 120 or so). Is there any other way to rais the BLM besides adjusting the FP?

 

[bison]

same here ive been averaging about the same in the city since my rebuild. Ill be driving it down to florida tonight and will see how much im getting on the hwy. Prior to my build the highest i seen on the hwy was about 19. By the way my BLM while cruising is on the low side of the 128 mark(about 120 or so). Is there any other way to rais the BLM besides adjusting the FP?

First make sure that no ambient oxygen is getting in the exhaust. If not then id get a new chip. Ive seen problematic MAF's reading wrong and causing poor economy too

 

[GNRick]

I don't know if larger injectors have anything to do with it but I suspect they do. My mostly stock 87 TR with stock injectors, stock turbo, stock transmission, Dutt neck intercooler, pypes exhaust and 3" downpipe (well, maybe it's not mostly stock) and Full Throttle chip gets 18-20 hwy and 15-16 city. My 87 GN with 009's (soon to be 60 pounders),3200 stall, 3"DP, ATR exhaust and TT chip gets 13 city and around 19-20 hwy. I've tried checking both cars without getting into boost and this is what I come up with. Both cars run real good, no hesitation, pops, or sputters.

 

[Timbuick]

My mileage isn't great either. Cruise/accelerate BLM are good at a little either side of 128. But, at idle can read 142.
The TT chip removes the closed loop at idle (am i right?), which i've heard causes the car to run rich.
Also, in my case my IAC counts are also high and need adjusting. These maybe issues that cause poor mpg or others too, I guess.

 

[LS954]

Well since leaving va with a full tank I ended up refueling at 196 miles and about 3 gallons left, about 12 mpg. That sucks! not once did I get on the boost but my blm are at 118 on cruise. Last year I made this trip wit my old motor and the maf sensor that came wit the car, dont know what brand, I was making around 19 mpg.

 

[TLI]

The really wierd thing about this whole deal is that I got a E85 chip from Eric about a month ago and straight E85 is 10 to 11 same driving conditions???

Go figure.

P.S. No other cahnges other than fuel and chip.

 

[matt94z]

Wow! I get like 12mpg's maybe and my car just has a chip, 3" exh and home made cold air. I know my car has issues though. My BL is at 150 @ idle.

 

[bison]

Well since leaving va with a full tank I ended up refueling at 196 miles and about 3 gallons left, about 12 mpg. That sucks! not once did I get on the boost but my blm are at 118 on cruise. Last year I made this trip wit my old motor and the maf sensor that came wit the car, dont know what brand, I was making around 19 mpg.

If its cruising at 118 its rich and probably cant pull enough fuel to get to 128. Thats part of the problem. What O2 sensor

 

[Dr.drivability]

Have you check you rpms? Count the shift and see if you are going into 4th. If you are in 3rd your rmp should be high. If you have a non-lockup convert it will make a difference. I have not check my in town mileage, but my highway is around 24-25 mpg at 70 mph and my rpm is around 2400. I have a vigilante non-lockup converter and 70 lbs injectors. Have you had a compression test? You may have some bad valves.

x2 I have a vig, but lock up w/ 3:73 gears 22 to24 highway

 

[Shanespark]

The 5 volts you are reading is the reference voltage supplied to the O2 sensor, you are correct the voltage should fluctuate above and below the reference voltage, it is not going into closed loop operation in which case the o2 sensor sends a signal to the computer related to oxygen content of the exhaust gas.

 

[Chuck Leeper]

???

The 5 volts you are reading is the reference voltage supplied to the O2 sensor, you are correct the voltage should fluctuate above and below the reference voltage, it is not going into closed loop operation in which case the o2 sensor sends a signal to the computer related to oxygen content of the exhaust gas.

Huh??

 

[GNRick]

x2 I have a vig, but lock up w/ 3:73 gears 22 to24 highway

I've never gotten that much mpg. Do you have a chip with "lean cruise mode"? I also have a lock up vig.

 

[TLI]

I just filled up yesterday and went 115 miles (GPS) and put 9.1 gallons of E85 inthe tank. I don't get much better with the alky chip and 91.

 

[LS954]

If its cruising at 118 its rich and probably cant pull enough fuel to get to 128. Thats part of the problem. What O2 sensor

Not sure but i believe the sensor was replaced when the motor was redone. Ill find out from my mech.
Also at around 60 mph my rmp are at around 2k