Drop in gas mileage

Hi there,

apart from the normal tune items that can affect fuel economy, often over looked is the 02 sensor, these should be replaced periodically, what they will do is as they age they will start to slowly fail, now as they may still send input into the ECU no fault code will result, but they can send incorrect information and when they start to fail they will send information that require the ECU to richen up the mixture and this will result in higher fuel consumption, so do the full tune and have the 02 sensors tested as well, start here.

mark (mhpautos)

I recently got a new used car that was my dad's business vehicle, and I am experience fuel economy issues.

Right before I bought it, the check engine light came on and my dad took it to the shop. They said it needed new spark plugs and wires. A few weeks later, I took over the car, and it went from its normal 22 - 23 to about 12 mpg. We changed the plugs and wires and it seemed to fix the problem as I got 26 mpg on the way back home. However, the problem is still there. It seems when I drive the car from in one trip, I get really good fuel economy. When I drive the car over the period of a week or so, I get poor fuel economy.

I think that the problem may be the fuel pump or a leak in the tank or lines somewhere. But, before I go all gung ho about that, I wanted to know if I should try something else. I was looking at those fuel injection cleaners sold at department stores and I thought I might try one of them.

Any suggestions?

You should be getting more than 12MPG. I think they average around 18MPG. With almost 150K on it, I would question if the catylatic converter is plugging. Also, is the car hard to start at times, especially after sitting? If not, chances are there is no fuel leak. Has the check engine light come on?

Let me know.

I have been having poor gas mileage for a few mos. now. Also, when I accelerate going up a long hill or incline the engine "misses or lurches", also does this sometimes when I am at a stop light. I changed the air filter, had a tune-up including new spark plugs, spark plug wires, fuel injection cleaning. No improvement. Then there was an episode where the engine light came on and it was almost like it lost power, engine missing big time. Took it into the dealership and they ran a diagnostics. They replaced the cam/crank sensor and also did a software update on the main computer of the van. No change again. Then the engine light and power loss thing happened again. The dealership said it gave off the same codes, but since they had already taken care of those two issues, they test drove it. Said they did not notice any missing. They now want to have it for the day to put in on a "flight plan" (?? ). I have said to everyone who looks at the van that it seems to be something with the gas and/or emissions but no one seem to go in that direction. I have had a few ex-mechanics mention the EGR sensor or valve and also the gas pressure regulator (??). What direction should I be heading with this issue. I am getting tired of running it into the shop and have spent around $1000 now with no improvement. Thank you!!

you already gave the dealer $1000 to fix it !
AND the same codes are back so its still their problem
so they need it for a day let them have it for two as long as they ll. give it back all fixed
good luck