trouble with gas mileage

[97neonND]

I have a 97 neon and have only put after market exaust on it. I just redid the head gasket and everything on it and am now having some trouble. The dealership I bought the car from did something to the damn check engine light so now it doesn't work, which in turn means I can't pull any codes from just doing the on/off on/off on trick with the key. My problem is I used to get awesome gas mileage with the car. But now I can fill it and be one empty two or three days later. I can smell the exaust and I can tell it is running way, way rich. People have said Oxygen Sensors could be a good possibilty but from mopar they cost a little over $200 for both of them. OUCH! Can anyone give me any other pointers????

[71RR]

If it's an O2 sensor problem all you need is the first one(the one in the exhaust manifold/header). This is the one that tells your computer the A/F ratio, the one after the cat tells it weather or not your catalytic converter is bad.

[95sprtcpedrvr]

I replaced both of my O2 sensors on my 95. I got a borg/Warner universal type from Advanced auto for $68 and the exact replacement was for a li'l more so I got both of them for less than $200.

[dwc43]

Sounds like they got the dual cams out of phase with each other. I bet that is where your problem lies with milage. HAve you checked to see if the engine light bulb is blown. IT's just a normal bulb and they do go bad.

[neonhondakiller]

O2 sensors will cause a milage prob
and a exaust leak too i would check bolth

i am geting 35 mpg and my car has a lot of mods

[flight704]

the neons use the obdII on board diagnostics . you need a scanner to down load the codes. my neighbor has one and i just use his. advance auto sells them they are not too expensive also snap on has one too its a little more expensive my neighbor is a goodwrench tech and he told me they stopped the key thing stopped in like 93 or around there when they went with the obd systems. i tried it on my 98 wrangler when he told me that mopars cant do that anymoreand it didnt work. I just assumed he was correct. I have never tried the key thing on my 96 neon but i will today , i could be wrong and it wouldnt be the first time either lol

good luck and i hope this helps

[mrmonro]

go to advanced auto or autopalace and have them scan it for free... the bulb is probably blown, in which that case its a 10 minute replacement... howevere if the obd11 scanner picks up an o2 sensor/ and a catalyst monitor code (do not replkace them right away) pay a dealer or local shop that has an otc scanner or snapon scanner to monitor the sensors.... then buy what you need.... those sensors are the first thing (usually) to set the ck engine light on..however something else may be telling them false information... i have also seen both sensors go bad after a headgasket replaement due to cooland/oil burning deposits on them too.... dont be hasty spend the $50 or $75 dollars to have them monitord GOOD LUCK!!!