I recently purchased a 1996 chevy cavalier with 171k the majority of the miles were all highway miles it was an older guys car who used it to go to college about 150 miles away from his house.. So the car is in great shape other then his rattlecan paint job on my to fix list..

Heres how the problem started... Owned the car for a cople months and decided well im going to put a bit of money in it since its running really strong and seems pretty reliable.. so i started off with a " Cold Air Intake" reset the computer by dissconecting the battery and started it up it was a bit grumpy at for a min or so and ran just fine after.. waited about a cople weeks changed the spark plugs which were aparently already new.. but oh well.. cople more weeks i ordered headers and installed them and had a full exhaust to done as well.. Thats when the problem started.. as soon as the headers and exhaust went on the car started running really rich "its buring the new catilitic converter" NEVER ran rich before i changed to headers and exhaust. also its begun to back fire once out of about every twenty starts.. anyone got any ideas?

how have you determined it's running rich? what plugs did you buy?



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Guy at the exhaust shop to took it back to said it was rich. he cut the exhaust back apart to look at the cat and it had turned white inside? He said typicly that means to much fuel. Spark plugs are bosch iridiums. same type that and part number as the set i pulled out of the car

Did he redo the location of the O2 sensor? Maybe it's not getting an accurate reading if it's spaced too far out of the exhaust flow. Or maybe he totally f'd up the sensor if he reused it. Just my guess. Good luck!

Its still the old sensors.. the o2 location for the up stream sensor was moved down the exhaust about 3 inches because the headers port location for it.. and the down stream sensor was moved forward about 2 inches from stock location to a mounting hole that the factory put in the exit of the catalitic converter... Ive already got new o2 sensors on the way from rockauto wont be here tell the 12th tho

White is usually a sign of a lean mixture. Without a wideband you will never really know. You can read the plugs for a better idea over reading the cat.

Your problem is likely O2 sensor related. Probably need to do a heated O2 sensor in the primary position.



FU Tuning

Also, get rid of the bosch plugs, and if you ordered bosch o2 sensors, send them back too. Also; your exhaust guy has no idea what he's talking about. White=lean, black=rich.



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My car ran better when I put a heated primary o2 sensor. I agree with the above, white = lean which is probably bc of the primary o2 sensor being off.


PSN ID: Phatchance249

damn i dont wana put another 60$ sensor in the car.. the heated rear ones enough.. how do you even add a heated sensor in since the primary is unheated?

im going to try just replacing the two with stock replacements and see what she does if im still having problems ill replace the fuel pressure regulator then up to a heated o2 sensor

pull the plugs and see what they look like, post a pic if you can.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs

there is a write up on here that I contributed on. Basically I got a universal heated 4 wire o2 sensor, cut the plug off the factory 2 wire connected it to the appropriate two wires on the sensor, and tapped into the two power wires for the rear sensor. Works great. I would run some fuel system cleaner through it, could have gunky injectors limiting your fuel.


PSN ID: Phatchance249

ill pull them while im at work today if its dead.. ive already ran an entire big bottle of lucal fuel system cleaner.. im talking like the 32oz er used it over 4 full tanks of gas..

i though the primary sensor was only 1 wire?

that fuel system cleaner was a waste of money. not really contributing anything to your problem i know but just thought you should be aware for future

I agree. Rather use seafoam than Lucas


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no need to product hate come one.. seafoam here is way to expensive $12 a can i think not.. the lucas was only $6

I think the earlier LD9's had a 1-wire, forgot about that. Not sure what to do then.


PSN ID: Phatchance249

Location of the IAT sensor can cause some issues as well. And the Lucas CAN cause spark plug discoloration if used excessively.




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Nobody has asked and OP hasn't stated whether the CEL light is on or not. One time I forgot to plug in my IAT and the car ran rich as could be and wouldn't idle for anything.


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs

Check engine light is NOT on it does however randomly come on then go right back off after like 5 min. IAT sensor is literly exacly were it was in the stock airbox. i get my new heated o2 sensor's today so hopefully that will take care of things

Shawn McKenzie wrote:I think the earlier LD9's had a 1-wire, forgot about that. Not sure what to do then.

Use to be a kit for the 1 wire systems to do a heated, but still not much different than doing it on a 2 wire system.



FU Tuning

Ok so i have a second heated o2 now and need some info on converting it... i know what wires do what on both plugs 2 are heater wires 1 is a ground and 1 is the sensor wire correct? so if i splice the new heated o2 into the other o2 sensors heater wires and ground wire it then hook its sensor up to original senors plug it should work just fine correct? or do i need to run it its own heater and ground wire?

I'm having the same problem in my 2003 cavalier...right after putting in a full exhaust I'm getting consistently 20 mpg regardless of driving style and no i dont put my foot down more just to hear the noise, my driving style has remained consistent. Pulled the plugs today and each looks brand new, the a/f gauge reads between 14.2-15.7 at idle and cruising going down to around 11.7-12 at wot which seems normal to me. Anyone have a solution? Also replaced the upstream o2 sensor and no change and these are already heated in my year if im not mistaken

So it seems the universal heated o2 in the upper locatin has fixed half the problem also found a broken vacume line leaving the throtal body repalced that and shes back to runing like a champ thanks guys! sorry i took so long to repost wanted to give it awile to make sure it was really fixed