I have a 99 rodeo with 100,000 km's on a 3.2L. I recently had problems with a check engine light on due to the mass air flow sensor and the intake gaskets and a surging problem. I also noticed it was starting to use more gas around that time as well. I replaced the sensor, intake gaskets and the surging seemed to have gone away except the odd occassion it does it on start up. I noticed the gas mileage is getting worse. This morning my check engine light came on after i filled it up with gas. Still seems to be running fine and cant smell any gas leaking.
I need some help as i dont know if it could be a plugged fuel filter, fuel pump maybe going? I read somewhere here that there maybe a TSB for the pump or something? I still have to get it in and see what code it comes up with.<img src="/forums/images/graemlins/confused.gif" alt="" />

well, first find out what that CEL is for. Second, suspect your O2 sensors.

Might be due to, colder weather, winter grade gas, dirty PCV valve, dirty EGR, dirty fuel injectors, low tire pressure, front and/or rear end needs to be aligned, dirty air filter, weak battery or weak alternator. If you replace or clean any of the above pieces make sure you disconnect the battery for at least 15 minutes so the ECU will recalibrate itself.

For more FAQ see the link in my sig.

Before you disconnect the battery though, take it to an Autozone and have the code checked out. They do it for free. If you suspect the fuel filter, then change it and see if that makes a difference. Personally, I try to change mine every year. Since you still have the occasional surging, I'll bet you've probably got some lean left/right bank codes. Sounds like a vacuum leak somewhere. Check for any hardened/cracked vacuum lines. Good luck.

Alin

What a goofy truck i have. I went out at lunch yesterday and started the truck up to go out and the CEL light went out and stayed off. Gas mileage seems a bit better (wont be able to tell until i fill up again)but still have the surging sometimes. I had to order the fuel filter and it should be here soon. I'll check for a vaccum leak. Is there a shop manual out there yet for the 99 Rodeo? I can find a Haynes manual for older ones but i think they changed some things for the 98/99. Thanks for all the help. <img src="/forums/images/graemlins/cheers.gif" alt="" />

It sounds like an intake manifold gasket may still be leaking to me. Good luck with your troubleshooting.

Just an update - Well it turns out i had 2 totally dead 02 sensors. I have replaced them and a fuel filter but not sure if it has totally fixed the mileage problem. I could only get 2 of the 4 and am waiting for the other 2 to come in so i can replace them as well. So far CEL is staying off. Best mileage i had with my truck is 27 mpg on long hwy trip. Right now is is getting 19 mpg for shorter trips and cant find a leak anywhere. Hopefully replacing the other 2 will make it just like a new truck. <img src="/forums/images/graemlins/cheers.gif" alt="" />

I wonder what kind of gas, what kind of 'miles' and
what kind of 'gallons' you guys in Canada have
to get 27 (!!!) miles per gallon ! Here in USA we can
get 27 MPG only in cars.

Oleg

I'd say you are doing well to get 19mpg. I'd say most of us would be pleased to get 19 on short trips.

I would make sure you NEED to replace the o2 sensors before you shell out that kind of cash, those things aren't cheap and it sounds like you are having it done, so that adds up to even more.

Have your codes read, and post again. I would unhook the battery for a while as well and then give it a few days of driving. Then see what your milage and power levels look like.

My boyfriend happens to have his own mechanical/autobody shop so I get a special rate. The short trips are a commute to work-about a 20 min dive one way on hwy. I had the 2 front 02 sensors tested as someone had sugggested here and they were very bad so i replaced them but now the CEL came on this morning and has now since gone off again. It seemed to do this last time and then it came on again a day or so later that's when it came up with the o2 sensor codes. Im still not getting the mileage it should be so i have to wait for the CEL to come on to read the codes. Im guessing it is the back two now. It seems to be my luck with this truck lately. Dont know what else it can be. Just for reference 02 sensors in Canada range from $80.00 each for aftermarket and 175.00 each for OEM. Thanks for the input.