A theory

[Thumper8302]

last couple of days i have been thinking about of couple of issues i am having with my kon...first off the basics... its a 2001 xl, 239,836 miles on the clock, 2wd with the 5.3..... i had stated in one of my first threads i had taken a trip out of town to see a buddy and wound up receiving the p0430 code.... now i bought the kon back in jan and have been having idling issues ever since.. ive ruled out the alternator, fuel system, and vacuum systems. since the trip i have replaced the pass rear o2 sensor, had my cats flow tested, and had the code cleared.. Now i remember when i had taken that trip right after i had gotten off the highway i had hit some construction and due to some crazy drivers i was forced to hit my brakes.. a couple of turns later is when i had noticed the cel.......

after i had the o2 sensor replaced and the code was cleared all was great for around 2-3 weeks until some idiot had pulled out infront of me causing me yet again to slam on my brakes. i looked down and bam the cel was on again.... had the code scanned and it was the same o2 code... i have not had any performance issues like loss of mpgs or rough running....

Truck runs great under throttle..... Lets say im in gear and i turn on my ac.... ac kicks on and my rpms drop to around 300... as rpms drop the voltage drops for a few seconds until the vehicle slowly corrects itself..... Voltage needle goes from just under 14v to halfway between the 9 to 14v levels... Same results happen when im coming to a complete stop especially at night when my alternator is under even more of a load from lights...


So heres my theory... When the voltage drops, i think the electrical system is starving itself. I have a dirty throttlebody and will be cleaning it this weekend.... I dont think the iacv or in my case the idle air control motor is workin right so the computer changes the fuel mixture to bring the idle back up... which incase would cause a rich or lean mixture to be read by the o2 sensors throwing the code... OR.... when the voltage drops the o2 sensors are not reading to their full potential giving a false reading causing the code to be thrown.....


so now im going to sum this all up into one question now that u all know what my thoughts are...... Would a bad Idle air control valve or motor that causes the idle and voltage to drop cause false readings in the emissions or hell, anywhere in the electrical system that would throw a cel?

Any thoughts????

 

[Thumper8302]

bump?

 

[Redhoe01]

Man, I wish I could help you but I am not sure. Nice to hear tho that your truck has 239,000 on it and still running.

 

[highrollin113]

i feel like you jinxed me, my yuk has been fine till i read this thread and BAM!!! cel, lol, i do not know what code it is yet and it seems to run fine no idle problems or under throttle

 

[Mac]

Dude it's a hard read.

Your truck is now running at 240,000 miles (Damn..very nice!)......Let's think about this for a second now.

P0430 keeps popping up because the O2 sensor is reading the Catalytic Converter and I suspect the CAT is dead.

Which Bank and sensor is the code from?

 

[Thumper8302]

man my bad ryan.... its all good tho man ur not alone... my boss called me this evening and he is having tranny issues in his altima..... and mac, i agree its a hard read.... but i had taken it to a muffler shop before hand and they had done a flow test and some other things to it and were confident in tellin me that the cats were good.... ive been goin to them for 11 years and i do trust them..... but the p0430 is catalyst efficiency low on bank 2... so the sensor would be on the passenger side downstream....

now i have had the code cleared now twice and the only time it had come on was after an issue that required hard breaking.. (also remember my idle isue i had been having causing the voltage to drop)... ive driven around 2000 miles and have had no issues with the o2 sensors but those 2 times....

 

[2000Yukon]

I had a ground issue and when I would come to a stop rpm's would drop and slowly come back to normal. Turns out it was one of my grounds.

 

[Mac]

"p0430 is catalyst efficiency low on bank 2... so the sensor would be on the passenger side downstream"

So you're telling me that the code is from the passenger side 02 behind the Cat.
Ok then. Since you said that you change that O2 before, that leaves the sensor from being the problem.
I'm really putting my money on the CAT as being bad. It may not restrict air flow but it could be contaminated (oil)or simply not working properly anymore. You could also check for exhaust leak, that could set the code off.

(Your Truck running at 240k...I'm still betting all my money on your CAT being DEAD.)

 

[Thumper8302]

"p0430 is catalyst efficiency low on bank 2... so the sensor would be on the passenger side downstream"

So you're telling me that the code is from the passenger side 02 behind the Cat.
Ok then. Since you said that you change that O2 before, that leaves the sensor from being the problem.
I'm really putting my money on the CAT as being bad. It may not restrict air flow but it could be contaminated (oil)or simply not working properly anymore. You could also check for exhaust leak, that could set the code off.

(Your Truck running at 240k...I'm still betting all my money on your CAT being DEAD.)

if it is contaminated with oil what should i look for on the cause of it becoming contaminated?

 

[Mac]

All engine over time will consume oil due to internal wear, and those oil will eventually make their way down the exhaust system.

(Dude!!....you could change the Cat or keep on guessing....take your pick)