83s bad gas milage
03-06-2006, 07:08 PM
#1
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83s bad gas milage
So far I found that the FP reg and pulse dampner were all leaking, so I replaced those, did the plugs wires cap and rotor.
Plugs are the right color.
I am still getting about 7-8 mpg around town with some highway, but I do have a lead foot.
I assume the 83 is speed density.
I also talked to Gilbert at Vertex, and he said terrible gas milage on an 83 was usually the sign of a computer problem, and he did not seem to think that the o2 or any of the temp sensors were the problem.
Before I haul off and buy a new computer I dont need, does anyone have the ohm ranges of the temp sensors, and the air flow meter.
Also what is the number for the correct size injectors. (never can tell)
It does seem like its getting worse, but my car runs very good.
Anybody else with an 83 or 84 solved a problem like this.
Gees I am almost beginning to suspect a fuel leak, but I dont smell anything and can see no signs of a leak.
Plugs are the right color.
I am still getting about 7-8 mpg around town with some highway, but I do have a lead foot.
I assume the 83 is speed density.
I also talked to Gilbert at Vertex, and he said terrible gas milage on an 83 was usually the sign of a computer problem, and he did not seem to think that the o2 or any of the temp sensors were the problem.
Before I haul off and buy a new computer I dont need, does anyone have the ohm ranges of the temp sensors, and the air flow meter.
Also what is the number for the correct size injectors. (never can tell)
It does seem like its getting worse, but my car runs very good.
Anybody else with an 83 or 84 solved a problem like this.
Gees I am almost beginning to suspect a fuel leak, but I dont smell anything and can see no signs of a leak.
03-06-2006, 08:01 PM
#2
Nordschleife Master
0. You have a Private message.
1. 7-8 mpg is a bit low for freeway. Since it doesn't seem to matter if your intown, or not, something is weird.
2. The 1983 US 928S does not use a speed density system. It uses an air flow control system. It has a barn door type sensor that measure the volume of air, and the tempreture of the air, that the engine injests. It then does a calculation to figure out how much fuel is needed. The system is called L-jet.
3. There are many many things to check other than replaceing the EFI computer system. I do not know Gilbert at Vertex, he may be good, and I won't want to talk bad about someone I don't know. However a mechenic that suggests that the most common problem with the L-jet fuel system is the control unit is generaly NOT a good at fixing the L-jet EFI system. The control unit is very reliable, and should be the last thing you check.
4. What would I check? Here is the list.
Cold start injector
Cold start injector tempreture/time sensor
Temp II switch
Vacuum line to the distributer (a vacuum leak or clog to the distributer can prevent it from getting proper advance)
Leaking injectors
cloged cat
proper fuel rail pressure
O2 sensor
Air Flow meter (unlikely IMHO, but that's what it ended up being in my car.)
I think that rounds out the lot.
I'll see if I can't put up the requested data.
1. 7-8 mpg is a bit low for freeway. Since it doesn't seem to matter if your intown, or not, something is weird.
2. The 1983 US 928S does not use a speed density system. It uses an air flow control system. It has a barn door type sensor that measure the volume of air, and the tempreture of the air, that the engine injests. It then does a calculation to figure out how much fuel is needed. The system is called L-jet.
3. There are many many things to check other than replaceing the EFI computer system. I do not know Gilbert at Vertex, he may be good, and I won't want to talk bad about someone I don't know. However a mechenic that suggests that the most common problem with the L-jet fuel system is the control unit is generaly NOT a good at fixing the L-jet EFI system. The control unit is very reliable, and should be the last thing you check.
4. What would I check? Here is the list.
Cold start injector
Cold start injector tempreture/time sensor
Temp II switch
Vacuum line to the distributer (a vacuum leak or clog to the distributer can prevent it from getting proper advance)
Leaking injectors
cloged cat
proper fuel rail pressure
O2 sensor
Air Flow meter (unlikely IMHO, but that's what it ended up being in my car.)
I think that rounds out the lot.
I'll see if I can't put up the requested data.
Last edited by ViribusUnits; 03-06-2006 at 08:26 PM.
03-06-2006, 08:51 PM
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1. 7-8 mpg is a bit low for freeway. Since it doesn't seem to matter if your intown, or not, something is weird.
Thats mixed leadfoot driving. On the highway only it does better, but still not where it should be.
2. The 1983 US 928S does not use a speed density system. It uses an air flow control system. It has a barn door type sensor that measure the volume of air, and the tempreture of the air, that the engine injests. It then does a calculation to figure out how much fuel is needed. The system is called L-jet.
3. There are many many things to check other than replaceing the EFI computer system. I do not know Gilbert at Vertex, he may be good, and I won't want to talk bad about someone I don't know. However a mechenic that suggests that the most common problem with the L-jet fuel system is the control unit is generaly NOT a good at fixing the L-jet EFI system. The control unit is very reliable, and should be the last thing you check.
Thats what i thought too, but he is very experienced. He is the only person down here I would trust to rebuld an engine or trans. Maybe he was trying to make a sale or maybe he has run into it a lot.
4. What would I check? Here is the list.
Cold start injector
Cold start injector tempreture/time sensor
Temp II switch
Vacuum line to the distributer (a vacuum leak or clog to the distributer can prevent it from getting proper advance)
I also thought about retarded spark.
Leaking injectors
cloged cat
No cat
proper fuel rail pressure
New FP regs
O2 sensor
Have not checked that yet
Air Flow meter (unlikely IMHO, but that's what it ended up being in my car.)
I'll see if I can't put up the requested data.[/QUOTE]
yes if you could send me a link to the resitance readings, that would help.
Thats mixed leadfoot driving. On the highway only it does better, but still not where it should be.
2. The 1983 US 928S does not use a speed density system. It uses an air flow control system. It has a barn door type sensor that measure the volume of air, and the tempreture of the air, that the engine injests. It then does a calculation to figure out how much fuel is needed. The system is called L-jet.
3. There are many many things to check other than replaceing the EFI computer system. I do not know Gilbert at Vertex, he may be good, and I won't want to talk bad about someone I don't know. However a mechenic that suggests that the most common problem with the L-jet fuel system is the control unit is generaly NOT a good at fixing the L-jet EFI system. The control unit is very reliable, and should be the last thing you check.
Thats what i thought too, but he is very experienced. He is the only person down here I would trust to rebuld an engine or trans. Maybe he was trying to make a sale or maybe he has run into it a lot.
4. What would I check? Here is the list.
Cold start injector
Cold start injector tempreture/time sensor
Temp II switch
Vacuum line to the distributer (a vacuum leak or clog to the distributer can prevent it from getting proper advance)
I also thought about retarded spark.
Leaking injectors
cloged cat
No cat
proper fuel rail pressure
New FP regs
O2 sensor
Have not checked that yet
Air Flow meter (unlikely IMHO, but that's what it ended up being in my car.)
I'll see if I can't put up the requested data.[/QUOTE]
yes if you could send me a link to the resitance readings, that would help.