1986 volvo 740 bad on gas! Help

[rogerthechorister]

My owners manual for a 740 (but it's for my 1990 GLT, ie twin cam) says that the tank capacity is 13.2 gallons. Some others (later 960 for example) were I think bigger. That's why I asked you about YOUR tank capacity. IF you have a 13.2 gallon tank then I'd expect you to do at least 265 miles to a tank - at 20 mpg. If I drive my twin-cam gently on a run I can get 25, maybe even 27 mpg. But my V6 struggled to do 17 mpg and my 960 probably does under 20.

Are you SURE that your temperature senders are OK? Some cars have more than one, I think, and if you have a dud sender you may be getting put into "limp-home" mode which will be thirsty.

[richyrich514]

I changed the temps sensor
The only other sensor is for the temperature gauge

Im leaning towards the tps and the IAC

[richyrich514]

The idle has gotten worse

Cold start in the morning it wont start on the first crank and then when i crank it again it will shoot up to the 2000rpm area and stay there until i give her some gas ....

[baggy798]

What engine code is on the timing belt cover? If it's a B230F, you could try replacing the air mass meter with a second-hand one.

I think if the air mass meter has gone skewiff, it can affect the idle and fuel consumption, as well as general running (like hesitation, etc.).

It's all just a wide guess on my part though, I don't know much!

[richyrich514]

Update!

Changed the tps and iac and the idle issue has been resolved

BUT im still not getting good gas mileage

When i do the first cold start in the morning if i dont let her warm up and i leave right away, she feels like shes struggling to get going. After she warms up that doesnt happen again..

Next things on my list would be 02 sensors and fuel pump?

Thanks guys!

[Dirty Rooster]

Rich I keep a close eye on my actual petrol mileage by only ever filling it with exactly 10 gallons every time, running it down to the fuel light (there's about 35 miles after the light goes on so I'm never stuck for a petrol station) then zeroing the trip button.
This way each 10 gallon shows me my mpg (times ten, obviously) on the trip thing.
310 miles last one, 280 miles the one before.

If you do that it's easy and repeatable and gives you good warning of a problem.

Everyone says their method is accurrate but without actually measuring how much petrol goes in the tank you're just guessing.

[richyrich514]

I fill my tank to the top every time and reset the counter.. I can clearly see its not doing good. I guess 02 sensors, maf, plugs / wires etc should be checked

[richyrich514]

Originally Posted by baggy798

What engine code is on the timing belt cover? If it's a B230F, you could try replacing the air mass meter with a second-hand one.

I think if the air mass meter has gone skewiff, it can affect the idle and fuel consumption, as well as general running (like hesitation, etc.).

It's all just a wide guess on my part though, I don't know much!

Yea it's a b230f

[richyrich514]

Update

I have replaced the injectors... It is still sluggish on cold starts but not as severe as before. I dont have any check engine lights but im thinking either mass air flow ? 02 sensor?

I find it weird how after changing injectors it has cleaned up the problem a bit. So maybe the burned fumes hitting the 02 sensors is cleaner and thus helping the problem a bit????