hesitation, high cold idle and poor gas mileage

sd88supra · 01-30-2007, 07:15 PM

After getting 12 mpg, I took my 87 n/a to my mechanic to look for fuel leaks. He didn't find any, and told me it was most likely a bad o2 sensor. I replaced it, and it improved to 15 mpg. Still, its getting expensive as gas is a daily driver.

I thought that perhaps my mechanic missed a fuel leak, but after putting in a new o2 sensor the fuel odor went away. Also, whenever I go to fill my tank I hear the pressure come out. He said that given the high pressure in the fuel lines, even the smallest leak would be easily detectable.

Last time I changed my plugs and plug wires (in fact full tune up) was right around a year ago, 9k miles ago. I always keep my tires inflated correctly. And I've noticed that as my fuel economy has gone down the drain, my car idles around 1300-1500 when cold. When its starting to warm up, it idles around 1000 but a little unstable. Until its at ideal running temperature it idles fine. I also get hesitation when I accelerate (when cold, from 1500 rpm to about 2400 rpm), and whenever I keep it constant at 2000 rpm.

Plugs gone bad? I did a diagnostic and got code 71 (which I've had for a long time), but I had it even when I had good gas mileage.

01-30-2007, 07:15 PM	#1
sd88supra 3" Exhaust Join Date: Oct 2005 Location: San Diego, Ca Posts: 190	hesitation, high cold idle and poor gas mileage After getting 12 mpg, I took my 87 n/a to my mechanic to look for fuel leaks. He didn't find any, and told me it was most likely a bad o2 sensor. I replaced it, and it improved to 15 mpg. Still, its getting expensive as gas is a daily driver. I thought that perhaps my mechanic missed a fuel leak, but after putting in a new o2 sensor the fuel odor went away. Also, whenever I go to fill my tank I hear the pressure come out. He said that given the high pressure in the fuel lines, even the smallest leak would be easily detectable. Last time I changed my plugs and plug wires (in fact full tune up) was right around a year ago, 9k miles ago. I always keep my tires inflated correctly. And I've noticed that as my fuel economy has gone down the drain, my car idles around 1300-1500 when cold. When its starting to warm up, it idles around 1000 but a little unstable. Until its at ideal running temperature it idles fine. I also get hesitation when I accelerate (when cold, from 1500 rpm to about 2400 rpm), and whenever I keep it constant at 2000 rpm. Plugs gone bad? I did a diagnostic and got code 71 (which I've had for a long time), but I had it even when I had good gas mileage.