Knock and O2 sensor with a twist? HELP PLEASE!

[slickroper]

I need some of your wisdom guys. I have codes for a bad O2 (0503 -upstream) and the knock sensor (0304). I have had these for over a year and I would just reset the ECU (the car never "showed" symptoms)(I know it's bad) Anyways, I know the O2 doesn't kick in until the car is warmed up, and recently my car started showing symptoms right at startup and it continues even when warm, though not as bad. It runs like it has bad gas (best way to describe it, though not the problem) it will start accelerating and then hit a sluggish point and then come out of it. Sometimes multiple times during acceleration. Does this symptom point to anything in particular? I'm not about to replace either if not needed and since I'm at school my tool resources are limited. I also changed the temp sensor and spark plugs (KYB) a year back so I don't think they are to blame. I just haven't seen posts refering to this symptom as an O2 or knock sensor symptom.

If it helps, I get a real occational code (0307) "Unable to obtain a closed loop operation (right bank)" and (0706) "Fuel injection system lean or rich (right bank)" I guess if O2 is the problem, it's interesting it just started showing symptoms at the flick of a swich after two years of being bad. Thanks...

[Nahkapohjola]

Originally Posted by slickroper

...two years of being bad. Thanks...

Its money u need...
- to buy few O2 sensors, 6coilpacks, TPS, knockS - or cheaper car.
- std plugs last max 10k, use platinums

There are no such things as free miles or smiles.

[nissandoc]

what year is your car? 2000 and 2001 max's are notorious for air flow meter problems. that would explain the fuel system rich/lean code. the closed loop code is the 02 sensor, need to replace it. dont worry about the knock sensor code, its really not that important and doesnt really affect the performance of the car that much at all. air flow meter at dealer is about $115 but they require the ecm be reprogramed, make sure to replace the air filter as well, dont go cheap, buy one from the dealer. the air flow meter will cause the symptoms that you decribed, "bad gas".

[Nahkapohjola]

Some Facts:
- ign is retarded by ECU if Knock Sensor input is faulty. Retarded ignition causes poor performance and more than 10% mpg degrad. Pays to correct it. Replace or bypass; check page9 on link below... Note that bypass is not for every blondie.
- stealer$hip is the most expensive place to buy, never do that as u say youre low on money. (Note that u may get 3 dead reman MAF's in a row from Autozone). MAF 'Reprogram' claim is one of the ways stealer$hips rob u, ECU does that itself; reach exact info via clic clic clic 'Favorite Links' below...

[nissandoc]

just shows how much you really know nahkapohjola. you must own that website cause all you ever do is refer people to it. rather than giving knowledgable advice. i'm sure its helpful in some cases, but this guys problem is real world shit, something you obviously know nothing about. the "stealership" stuff is what ticks me off. the updated air flow meters have different parameters, thats why an ecm reprogram is necessary. but then again, you didnt know that. i,ve driven my 96 max for 100k with a knock sensor code and still get 24mpg, same as its always done. should he really go buy all new coils, a tps, and "a few" 02 sensors as you suggested, at maybe $500-$600, and then still have the same problem? thank god your not working on his car!

[Nahkapohjola]

Agreed, stealer$hips tick everyone off... they like very much swapping 800Euro MAF's w/o testing (like u suggest). They sure bill plugs not changed if youre not careful... But of course, there are some exceptions.

Note to Readers: do verify the Facts from the Nissan Field Service manual as suggested. Ask em' but dont trust em -or- stealer$hip style advice.

[slickroper]

Thanks for your help so far guys. Ya, I can't exactly replace everything, hence the point of the post to narrow it down.

My max is a 1995 GXE. I imagine the O2 sensor needs to be replaced like you said, but would that cause the immediate bad gas symptoms I'm getting right at startup? I understand the system can be retarded by the knock sensor code, but I've had the code for almost 2 years and it never hindered the car like this.

I am pretty attuned to the feel of my car and something is up and it sucks not to be able to put a finger on it and have it fixed.

If I replace to O2, the blinking code doesn't tell me with bank does it? I know there are a couple. And I found a good deal on ebay for one if it's the right one.
http://cgi.ebay.com/ebaymotors/O2-OX...spagenameZWDVW

Thanks again guys, I'll keep you posted...

[Nahkapohjola]

Originally Posted by slickroper

...would that cause the immediate bad gas symptoms ...

No replacements before testing. I just listed possibilities...

O2: During warmup O2 sensor has no effect: In this 'open loop' cold condition, ECU adjusts injection based on TPS, MAF, rpm input. After warmup, only tranny TCU uses TPS, now O2 replaces TPS in engine ctrl input (closed loop).
If O2 sensors fail, engine uses TPS, you cannot feel difference. Mpg is worse.

ECU has selftest for O2, you may also use dmm in testing O2: pulsing up/down between 0-1V. Measure from nearest O2 connector or at ECU; pins listed in the manual. The self tst code should tell; code reliability is sometimes a ?

"bad gas symptoms"
Whatever that means... If its only when cold, points to TPS. Measure for TPS linear resistance, Voltage at ECU. Clic and seek and clic the given links http://www.cardomain.com/id/pohjola#links. Check what u can do to TPS at http://www.cardomain.com/ride/748507/6

KS: Typical KS-failure causes ign retard (not always). Ign retard causes always performance loss & mpg loss, 10% or more. Depends on variables...

Coilpacks die due to driven miles, one by one. CamPos signal has to be good for good performance. Check groundings, connectors, See pages 9,10,14 on the mentioned link.

[slickroper]

I'm starting to think this problem could be not related to the O2 sensor at all. Maybe a bad spark plug or something? I just replaced the spark plugs a year ago but anything is possible.

[Mrbizness1]

I just had the knock sensor changed on my 96 Maxima. Under the new inspection rules in my state if the check engine light is on it doesn't matter how clean the motor runs you won't get a sticker. Most shops want to remove the intake manifold to replace it but I found a nearby shop on the web that changed it in 20 minutes. He even told me buy it on ebay to save money.

[FixUrNissan]

bottom line after reading all this mess. Runnig a vech for a considrible amout of time with a known bad O2 sensor can casue Cat Conveter damage . If your running to rich you will definitly cause Premature Cat failure. Emission warrenty to 8 years 80k miles normally on nissans .The knock Sensor Advances and retards Timing to help control engine ping. The Knock Sensor and the O2 Sensor should be replace, and YES THERE IS A ECM UPDATE. Nissans can check your ecm's # and see if ther are any updates for it. Like computers at home some times software improvements have been made later on after it was released. But if you don't ask they usually don't tell. MAF sensors True have been a cause of wacky problems like runing vechs to lean or to rich.

Recomendation. Replace your faulty O2 sensor , Replace your knoick sensor . You know they are bad? Then go ti your local dealer and get your ecm updated . I know it's going to cost alittle but this is the right way to fix your car. Besides there is a bulliten for O2 sensor codes for ealry 2000 model max's. It States to replace the bad O2 sensor and reprogram ecm.. So Start there first

Gl let me know how you make out

[Nahkapohjola]

Originally Posted by FixUrNissan

... THERE IS A ECM UPDATE. Nissans can check your ecm's # and see if ther are any updates for it. ...

Tell us:
- 1995 ECU sw versions that should be updated
- New version.
- Filename
- What problems the "ECM UPDATE" addresses
- How is this done...
- What "Nissans can check..."

If u cannot give exact answer, claim is balooney.