Poor MPG, help!!

[Beach Person]

Some similar symptoms to cam sensor fault or crank sensor fault but they generate an engine fault light. Fuel filter maybe some of what you say but not all maybe.

[SIAMBLUE]

I would guess leaky injector, instead of spraying it will drip, that would give you bad fuel consumption, to be honest do some tests, then go from there.

[ANDTWENTY]

Originally Posted by Beach Person

Some similar symptoms to cam sensor fault or crank sensor fault but they generate an engine fault light. Fuel filter maybe some of what you say but not all maybe.

I changed the cam seal where the sensor is just after having the car and all seemed okay but yea, I dont have a light.

Originally Posted by SIAMBLUE

I would guess leaky injector, instead of spraying it will drip, that would give you bad fuel consumption, to be honest do some tests, then go from there.

This has crossed my mind because when I accelerate hard it can be quite lumping and hesitate which makes me think a fuel issue? I might give them a check and replace the fuel filters too.

[ANDTWENTY]

I just went to check the injectors, I pulled the fuel rail out so the injectors were suspended and turned the key to the on position so the fuel filter was priming, checked the injectors and there is no fuel leak so the injectors aren't leaking. I then checked if they were opening and closing properly by putting a screwdriver to them and my ear and they all seam to be clicking evenly. So this rules out leaking and working? They could still be blocked or a bad spray pattern, would this be a cause of poor mpg? I saw on internet that a symptom of a bad fuel injector can be a bad idle which is something i have noticed when starting the car.

[clarkey1984]

I know on some diesel injectors something can wear and cause far too much fuel to be injected, we have a Chrysler voyage at work that over fuels and smokes like nothing I have ever seen because three out of the four are doing exactly That, although how rare it is, or if a similar thing could even apply for a petrol injector or injectors I don't know.

[ANDTWENTY]

Originally Posted by clarkey1984

I know on some diesel injectors something can wear and cause far too much fuel to be injected, we have a Chrysler voyage at work that over fuels and smokes like nothing I have ever seen because three out of the four are doing exactly That, although how rare it is, or if a similar thing could even apply for a petrol injector or injectors I don't know.

I hadn't thought of that happening other than leaking but i guess its something else to check, I think i'm gonna have to rig something up and give them all a test, they looked like they could do with a clean too so will probably do that at the same time.

The other thing that's now making me wonder is the O2 sensor, might give this a clean too? And airflow sensor?

[ww1dm1]

If your coolant temperature sensor peaks at 55degC - something is definitely wrong and it definitely negatively affects your MPG as the mixture is always richened artificially. And my something I mean either the thermostat is stuck open or the sensor readings drifted. Figure out which and replace either the sensor or thermostat.

[ANDTWENTY]

Originally Posted by ww1dm1

If your coolant temperature sensor peaks at 55degC - something is definitely wrong and it definitely negatively affects your MPG as the mixture is always richened artificially. And my something I mean either the thermostat is stuck open or the sensor readings drifted. Figure out which and replace either the sensor or thermostat.

The thermostat was the first thing I replaced, I saw that it was running too cool and it was a common issue so sorted it and thought it would be bad mpg over but no its still here.

[ANDTWENTY]

I recet the average mpg and deceided to drive as best i possible could on my way to college, its about 12 miles with mainly A roads, a mile or 2 of dual carriageway and a mile or so of traffic light section. I coasted where possible and didn't accelerate hard I managed to average about 36mpg which is good but when i got on the dual carriageway they just started falling, doing 50/60 in steady traffic on the A roads was fine, good mpg around 2500 rpm but as soon as i did 70 with around 3000/3200 it just started plummeted. I also had to nip across the city to get some bits and bobs and again my mpg dropped to about 25, i was still being careful but there was a few lights and slower traffic but is this really how it should be?

I picked up some quality spark plugs and put some premium fuel in so will see how that takes. I still have the issue of lumpy acceleration where it just hesitates like it has a choke!? and a slightly dodgy idle, it never drops below 1,000 and fluctuates between 1000 and about 1300? I'm thinking this is due to some blocked injectors.

[colnet]

Have you tried cleaning the icv (idle control valve) ? There is a how to, just do a google search.

colnet