themills

iTrader: (2)

I have been throwing a catalyst effieciency code P0430 off and on for a year now. It never effected anything so I just figured, It just was a bad cat. Recently the light came on, same code, but when I am driving really hard, wot, 4500 rpmish in 2nd or 3rd, it feels like the car "chokes". When it chokes... the SES flashes for a couple second and goes off. I guess my question is, Could a bad front o2 sensor do that to my performance or is it definately a "partially" clogged cat...? Would a bad front o2 sensor make the fuel mixture so rich my car would choke up at WOT, or would I just be getting bad mileage. If not, then it really is a partially clogged cat that can exhaust normal backpressue, but not WOT, I dont even know it that makes sense. Anyways thanks for the help.
I have a 5spd. Oh yeah and now the SES has been off except when the Max chokes.. it blinks for 20 seconds, then goes off and stays off.

NmexMAX

iTrader: (22)

Blinking SES typically = misfire which then usually means coils.

KRRZ350

iTrader: (29)

no you are right for thinking that as a possibility since you know that code basically means the downstream o2 is detecting an overly rich condition, But, it is more than likely the cat, I think this because you're upstream o2's aren't throwing any rich codes. I just noticed your car is cali spec, I don't remember what any o2 or cat differences exist between the fed's, but I would like to know. but regardles- You can check for a plugged cat or muffler with a vacuum gauge, the vacuum gauge should come with an explanation of the procedure to check for this, and it works maybe 80% of the time. It won't tell you which cat either obviously.

NmexMAX

iTrader: (22)

CPS + MAF @ 3000 + WOT = no use of o2 sensors, this is with respect to the 99 FSM.

So KRR, you're wrong.

The fuel wont get burned because of a coilpack, therefore letting unburned fuel clog cats, thus resulting in your codes.

themills

iTrader: (2)

Well before it happened, I had bought the car and noticed it had a slight misfire that wasnt even throwing a code, and after I fixed the plug, that bad catalyst code came up. I also had a bad coil pack a few months ago but changed it, it did throw a blinking SES but it stayed on longer than 20 seconds. Wouldnt a bad coil pack keep the SES light on?

From what I read I would have to drill a hole in my exhaust and weld it shut to test with a vacuum gauge.. I think not. heh

NmexMAX

iTrader: (22)

... ... ...

themills

iTrader: (2)

So a coil pack, would or wouldnt keep the light on all the time? It did the first time. I dont understand your ... ... ...

Would a bad front o2 sensor cause my car to "choke" and "buck" randomly when I am at WOT above 3000 rpms?

KRRZ350

iTrader: (29)

No the vacuum gauge hooks up to a vacuum source on your intake, if there is a plugged exhaust it will cause the negative pressure to drop after revving the motor up and down for a little bit, the instructions are specific to what rpms and how long to hold it and something about snapping the throttle and stuff, buy a vacuum gauge, you'll learn a lot just from reading the instructions that come with it, they can be very helpful for diagnosing a bunch of problems.
Yes that is correct that at wot the o2's aren't used, I didn't word that too well. What I meant is that when he's in closed loop (not when he's having the problem) that the upstream o2's are saying everything's cool but the downstream is saying it's rich, so it's highly probable that a cat is not operating effectively. Also, I notice no one on this site ever states there mileage and maintenance when there asking about a performance problem.
I didn't mention or suspect a coil pack because the ecu fires each individual coil and it knows if a single cylinder doesn't fire and he did not mention any misfire codes.
Also, I would have thought that your cat efficiency code would not be a ghost code, but I didn't know for sure and evidentaly must have been wrong.....

KRRZ350

iTrader: (29)

no it would not

themills

iTrader: (2)

Sorry, I have 130,000K

The cat effieciency code is not a ghost, I was simply saying that the light goes on and off, randomly. Like I said, when I am having the problem as I am driving the SES flashes, for the extent that I have the problem. Then no SES at all. I am definately leaning towards a bad cat, seeing as how you explained how the o2 sensors couldnt effect my peformance during open loop. As far as my maintence... Its good. New fuel filter, plugs, oil etc.. always as needed. But your right, even if my coil was only misfiring every so often, still seems like the light would be on for at least a few hundred miles, same for a bad spark plug correct?

KRRZ350

iTrader: (29)

Exactly, god I'd hate to see a spark plug that was soo wasted the max's ignition couldn't jump it. Thanks for the mileage and letting me know the fuel filter has been done, because unless you had a bad fuel pressure regulator, the cat wouldn't be likely to go under 90k, but 130k is probable, I've seen 300k and no problems but that doesn't matter, anyways yeah I suspect the cat.

themills

iTrader: (2)

Guess I will get a vacuum gauge though, heh, thanks for the help .

njmaxseltd

iTrader: (19)

Thats not a choke, it's a misfire. Your 99 is prone to bad coil packs which cause the misfire felt much more under a load. My 99 did the same thing, flashed the CEL every time it misfired, but it never identified which cylinder it was and the CEL never stayed on. I wound up replacing all 6 coil packs to resolve the problem. This is a common problem with 99's.

Your O2's are not taken into consideration by the ECU at WOT. However, you probably should replace them for better performance and gas mileage during normal driving conditions.

themills

iTrader: (2)

DO you have a link to the "better" mitsubishi packs, or I heard the 5th gen ones have the problem fixed correct?

KRRZ350

iTrader: (29)

Either way, regardless of whether you have bad coil packs, which you should at the very least test the resistance's first, and clean the grounds, but regardless you should deal with your cat efficency code, it sounds like its repeatedly coming up for you no? Is it there now? I've seen a melted cat, they operate at extremely high tempatures, if you do have that and have had bad coil packs in the past (that rhymes sick) then it's also very logical that the misfire caused unburnt fuel to reach your catalytic converter which would increase the 'catalyst reaction' thereby causing the cat to reach tempatures high enough to cause it to melt. Maybe this isn't the case though, but my question for those of you that had a misfire due to bad coil packs is Q: Did your ecu throw a cat efficiency code?

KRRZ350

iTrader: (29)

[QUOTE=njmaxseltd This is a common problem with 99's.
.[/QUOTE]
my freind was givin an offer from a tech at infiniti, to buy a motor from a '99 that had around 60k on it. The reason it was pulled from the car and needed an overhaul was because of excessive carbon build-up due to an o2 problem, he said this particular problem was common on '99's, I know your car is cali spec, and I don't know what sort of fix there was for this problem, all I know is what I stated above, but I'm curious if anyone else knows about this.
GO HERE SO AS TO NOT GET OFF TOPIC

I couldn't agree more with njmaxsled that 130k is past the life of the o2's, and you would get better gas mileage without a doubt! There going to start throwing codes at 160K anyways, along with the knock sensor,big bill to swallow but get it out of the way while you can.

themills

iTrader: (2)

Yeah, its is big to swallow,

When I just had a bad coil, It didnt throw anything but a misfire code, and an ignition code, but no catalyst efficiency code.

So I went driving hard tonight, and had a friend hit "read" on the scanner for the 16 seconds the SES would blinkm the car would stutter, and I could hear almost wooshing sound from the engine bay. Guess what, P0303 (0606) which is cyl. 3 misfire. So I am guessing it is an ignition coil, but why isnt my car storing the code? My cat efficiency has been going on and off for a long time, starting after I fixed a misfire, that I suspect was with the car a while before I bought it. So it is probably my cat is bad, and I will change it when I need to pas smog, but It appears my random flashing code is a misfire..that wont store... thats weird.

As to not start another threaD.... any suggestions on coils. Which mitsubishi's can I use, or is the 5th gen coils better?

KRRZ350

iTrader: (29)

sweet deal man, sounds like you know your stuff about cars, I'm impressed with the whole -live data- drivin' around with the scanner hooked up instead of geussing!

themills

iTrader: (2)

Yeah, well I still think my cat might be bad But I will fix this coil, then vacuum test, and I'll know for sure, without destroying it anymore if it still works... thanks for the help.

supadupa6

o2 sensors should cause the car to choke. however, they do play a MAJOR roll in fuel management. They'll kill your mileage if they're not working right.

Nealoc187

iTrader: (23)

My gas mileage wasn't affected when I had non working - and later non existent - O2 sensors...

njmaxseltd

iTrader: (19)

ECU runs a set A/F map under those conditions for optimum performance.

Incorrect data from a working O2 will cause more problems then running the car on a default A/F map.

KRRZ350

iTrader: (29)

I had one bad upstream, and one bad downstream, I went to put them in and found out nissan gave me the wrong upstream, I put them both in where they belonged, and cut the wires for the one bad upstream, It threw different fault codes and ran way better!

themills

iTrader: (2)

I suppose iy wouldnt hurt for me to at least change the main upstream o2, before the pre cat. I also suppose, the rear o2 being bad, could give a code to, but it seems like if the rear wasnt reading, I just wouldnt throw a code, if something was wrong with my cat, or very first 02 sensor

So, am I right in assuming maybe change the front right o2 and the one right after, even though my cali car has something like 4 o2 sensors.. or 3?

Nealoc187

iTrader: (23)

Didn't seem to cause me any problems when I did it.

KRRZ350

iTrader: (29)

I personally (keep in mind I don't actually live in cali, so I don't know how tough it is to get around this, plus I would probably have a hook-up somehow like I do here) but anyways, I personally would replace just the front o2's for gas/performance reasons, then I'd use a broom-stick instead of buying new cats, then I'd go HERE to buy some shady electronics

konak85

iTrader: (10)

Who knows what that shyt will do to you A/F ratio

KRRZ350

iTrader: (29)

It's for the 2 downstream sensors, which don't affect the a/f.