Contour Enthusiasts Group Archives Forums General Troubleshooting Lean Machine

My tour has been throwing a constant CEL for a while now, and finally today, I took it down to autozone to get it checked out (very nice guys, btw.) ODBII says 0171 and 0174 (Running lean 1st and 2nd bank). Any fixes? One of my buddies says it could be just because it's so darn cold here. Clean my injectors, perhaps?

Lean codes are usually caused by vacuum leaks (i.e. too much air) so you'd be better off checking for those first.

However, clogged injectors or a fuel pump that doesn't like the cold anymore (i.e. not enough fuel; usually associated with loss of power) can cause lean codes as well.

The last group of causes for these codes are bad combustion (i.e. too much unburnt air & fuel; usually associated with hesitation/surge and often caused by bad plugs/wires/coil(s)).

Good luck!

BTW, if you've over-oiled your K&N, you may have contaminated your MAF and/or IAT which would also pop lean codes (since the PCM infers less air flow based on the sensor reading than is actually passing through the MAF). You can eliminate this cause by reading the Barometric pressure from the PCM. If it is significantly low (<26"Hg and you aren't in the mountains or inside a huricane), then your MAF needs cleaning.

Wow, those are a lot of good calls. Thanks for the sugestions.

What I've done: The CEL popped up, which prompted me to cleaned my K&N filter. First time I've really done it, so it's possible I over oiled it, i'll check the maf. In addition, the fuel pump was replaced right before I bought it (about 800 miles/1 month ago), so i doubt it's that (but it very well could be!). if it IS plugs and wire...well DAMN, time for an upgrade! Thanks again!

My 95 has OBD-1 computer but reported lean codes when the O2 sensors were going. Sensors get weak and report a lean condition, computer compensates by richening up the mixture. Result: fuel mileage drops and dying 02 sensors still report lean mixture. CEL gets turned on.

If you do clean your MAF, make sure it's with either an electronic parts cleaner or throttle body cleaner. The other cleaners are too caustic to be used on those sensitive wires!

My own thought, though, would be to run this stuff called RXP (it's in a little red bottle at Autozone in the additive section) through your car after you clean out the throttle body and MAF. I was having difficulties myself with my 00' SVT starting up here early in the a.m., and doing the above mentioned items helped dramatically as well as improving throttle response and power.

Just my .02$

Electronics parts cleaner would be best - no chance of residue left behind by the cleaner.

Oops! I forgot the most obvious HEGO failure. I often assume that people have eliminated this cause before they start hunting around for more interesting causes. My bad.

what, exactly, is HEGO? And what the correct way to go about cleaning out the AMF and TB? The last thing I wanna do is take it to some monkey to do something I know I could do just fine on my own! :p

Oooh, I'll take the first part... Heated Exhaust Gas Oxygen sensor, a.k.a. O2 sensor. "Heated" because the sensor has a built-in heater element to maintain the platinum-coated zirconium sensor at the temperature required to function properly.

(EDIT: Here\'s a nice write-up on oxygen sensors , in case you're interested.)