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last time i mentioned this i got about 15mpg mind u my daewoo is 26 city 36 highway well since last report its gotten worse i am 1/8 below 1/2 a tank and ive only driven around 92 milees since fill up beginning of this month im not sure what to look for. the ripped hose i replaced didnt change the problem re-gapping plugs didnt fix this gas problem. my air filter is pretty much clean i cleaned the throttle body earlier this year i am really thinking MAF sensor but im not sure what to do i was thinking taking it to autozone tell them i need a scan but i did unplug my maf sensor one day b eginning this month so im not sure if a MAF code will show up from that or if a MAF code does show up im not sure if its because of a bad maf or cuz i unplugged it. i do have a map sensor too im just out of ideas i though ixing that hose and regapping plugs would have fixed it. What should i do?
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did you try replacing your ignition coil, wire set, and O2 sensor. also try cleaning your MAF sensor with MAF cleaner.
Lots of things can affect fuel economy, even some things that don’t seem related. Have you verified ignition timing? How about your exhaust, any leaks? Exhaust leaks, and especially leaks close to the exhaust ports at the cylinder head, can really kill fuel economy. Weak spark (perhaps due to bad wires, or cap / rotor) could be a culprit. Engine not warming up properly (perhaps the thermostat is removed, or stuck open) can cause poor fuel economy.
If the fuel milage used to be more normal while you’ve owned the car I would look at the service items first along with looking for any vacuum leaks.
If your car has OBD plug it in. Lots of parts shops will scan your car for free or if you bring a mechanic a coffee they will too. I know I would! Its such a valuble tool. It makes searching for possible causes of your problem so much easier and faster.
In any case don’t just throw parts at it. Investigate them first unless they’re due – as per milage interval – and you can afford it.
The very first thing I would check is the coolant temp sensor for the ECU. Some cars have 2 sensors. One for the ECU one for the dash. They don’t last forever and they tend to slowly fail rather than all of a sudden. When they completely fail all sorts of issues arise as the ECU cant properly fuel the engine for its temp, usually resorts to one fixed map and its usually rich.
You can test the coil positive and negative pols for resistance measurments. If its above the limits or close replace it. Coils are the most over looked tune up item. They do last a long time but like anything else will wear out. Weaker spark = weaker combustion, more fuel consumed.
Wires are the same. If the wires are within the spec leave em. If higher replace them.
Did you check the condition of the cap/rotor if equipped? If its a coil pack system check the resistance values against spec.O2 sensors last a long time but eventually fail. And they tend to fail over time meaning its not all of a sudden rather they just get worse and worse. Usually causing worse and worse fuel consumption and loss of power. If you drive around on a completely failed one you will run rich all the time.
Another thing to check is your EGR system if equipped. More often than not the ports are plugged up with soot and the valve still works just cant do its job. Early vacuum powered EGRs can be easily tested by at idle pushing up on the rubber diaphragm underneath it. This should allow EGR flow. If the engine runs very poor or stalls when you do this it works.
Also another good idea is to poor in a bottle of good injector cleaner into half a tank and go for a drive. Its argued weather its better to run cleaner thru the entire system vs just the fuel rail, but at this point for $6 its worth a shot.
Some mechanics don’t do this as it can dislodge varnish in the tank and plug up the filter. In some cases I agree but in my own car I run a bottle thru every oil change – as recommended by the manufacture and have had no issue. In that same breath I also change my fuel filter everytime I’m due for spark plugs for good measure. Fuel where I live is far from clean.
I would suggest that you make sure the brakes are in proper working order, if they are dragging the car has to overcome the friction of the brakes. Also have the alignment checked because if the alignment is off the tires are not pointing straight thus are rubbing across the pavement like erasers.
I have had people come in the shop complaining that the car has to rev real high before it moves, lo and behold the parking brake was on. 😳 :blush:The Coolant temp sensor (AFAIK I only have one) is not really accessable as it is under the Intake and my Temp light and gauge function normally so i doubt this is the problem. i was wondering about plug wires but i have no idea how to tell if wires are bad my car has a VGIS a type of electric ignition system and i have coil-on-plug setup.how does a O2 sensor cause that? AFAIK only the MAF and MAP control that? Vacuum leaks was a thing on my mind but i can only see 3 1/2 vacuum lines 2 lines are just after the Throttle Body one of them goto the MAP sensor not sure where the other one goes and between those two is a rubber plug the second vacuum line i see connects to the end of the thing the throttle body bolts to above the intake it makes a lever thing move when i give it gas the 3rd is the one for the Brake Booster. I do have a EFR system but AFAIK it would throw a code if something is wrong with it (Same for fuel injectors) Since my car dont show constant signs of fuel starvation and never stalls i dont think the fuel filter is the issue. Id be more than willing to dump a bottle of injector cleaner in the tank but is it ok to dump it in than gas up the car? will putting injector cleaner in there throw any false codes?
WTF is AFAIK?
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Sorry…couldn’t help myself :silly:
[quote=”AudioFunk” post=76756]I remember my car use to eat gas like crazy. I just needed to replace the spark plugs lol.[/quote]
well that is what i hoped would fix it for me but it didnt maybe i need new wires not sure i dunno how to tell if they bad my misfire didnt g away with the re-gap
Well i consulted a Mechanic and they told me i need to replace my Valve cover and plugs since the plugs are oil fouled, however, they did not answer me on if that is causing bad MPGs.
That is bad. To be that bad you have to have to be:
(1) Running the engine dead cold, like with no thermostat, so the ECU runs you at full rich.
(2) A bad temp sensor so the ECU just THINKS the engine is cold.
(3) A weakening O2 sensor so the ECU runs things rich.
(4) A partially plugged exhaust or catalytic converter.
(4.5) Ignition timing that is way late.
(5) A neighbor that is borrowing your gas.
[quote=”LeoTheLion89″ post=78189]Well i consulted a Mechanic and they told me i need to replace my Valve cover and plugs since the plugs are oil fouled, however, they did not answer me on if that is causing bad MPGs.[/quote]
The oil fouled plugs will be a contributor.
1. Not sure what you mean “Running the engine dead cold” Its around 40F this time of year or even colder.
2. I dont think a Temp sensor is a Issue my Temp guage works perfectly.
3. O2 Sensor is a possibility but i dont know if i have more than one.
4. I dont think Exhauset is pluged. When i stated the car after the plug regap the think bellowed thick white smoke for a good two minutes. Ignition timing could be a issue but my Timing Belt is not due for a change yet.
5. Impossible. I have what many Foreign cars have: a gas door that needs to be opened remotely my car is a lever others such as the VW Bug is a button.Also i have a leaking valve cover the mechanic i took it to to fix the brakes said its common with my engine. I plan on replacing the valve cover gasket anyway assuming i have a socket the proper size to take the nuts off with.
@College man:
I did clean off as much oil from the plugs as i could but considering that removing the plugs made the entire plug socket covered in oil and all the oil when into the cylinders when i removed them im sure they got full of oil upon putting them back in.
A few drops of oil are not going to wreck the plugs. And it’s unlikely your mileage could drop by half due to plugs, without you noticing major power loss and misfiring. And that much misfiring would burn up your catalytic converter and lodge a bunch of error codes. And it’s not dragging brakes, they would burn up in 2 minutes if they were dragging away 50% of the engine power. I would go with late timing or a slipped cam belt or a restricted exhaust as possibilities.
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