How To: Replace o2 sensor/fuel pump relay

[TimzSE]

Can someone talk me through replacing my front o2 sensor? And/or how much this would cost at a muffler shop? What benefits are there, since my CEL codes keep telling me it's broken (code 33)?

Also, how much do fuel pump relays cost and how hard is it to DIY? This is on the reccomendation of my dealership since my pump may be broken and not sending the correct amount of fuel, possibly causing my 300 mile plugs to burn up from being very rich?

Thanks for any and all help guys!

[Luke]

It's very easy, -disconnect the negative terminal on the battery-look on the exhaust manifold (right side of engine when facing the front of the car) and there is the 02 sensor, it has a wire coming out of it. unplug that-Take a wrench, i forget what size, and unscrew it and take it out-Take the new one and make sure you use the anti seize thread lubricant that it usually comes with, and put that on the threads screw the new one in, plug it up (assuming it's the universal one) -reattach the battery cable

I don't know about the fuel relay, sorry

[SPIRO]

code 33 could also be a timing problem and a variety of other things. Check your ignition timing with a timing light (15deg +_2deg for a SOHC at least). Set your idle for 750 if it isn't already and erase the code by switching to ecu mode 4 (i think) if you didnt already know to do so. Yup or its just your O2. Good luck!

[TimzSE]

Hmm, intersting. About three weeks ago my car wouldn't start, and it turned out my new, 300 mile bosch platinums had totally burned down and should signs of HEAVY richness (if I can borrow my roomies digi cam I will post pics, but they are in NO way what 1 month old 300 mile plugs should look like). The dealership reset my base idle and I replaced the plugs with OEM NGK's. I also had my intake manifold/thorttle chamber cleaned...they said there was tons of carbon build-up, but who knows. At the time (and still) I'm worried it was a bad fuel pump...but I was even more worried it was a broken timing chain. It wasn't, but the dealer-service department informed me the chain was 'stretched' (does this really happen?) and was causing the timing to be off. So, I had them reset it. What I find worrying is that on the same day I replaced my plugs I also had my transmission/diff fluids replaced, a crack on my exh. manifold welded, and my timing reset. Why is my engine slipping timing after only 3/4 weeks? Is this a sign of a terminal engine? Oy. I'm just worried. Anyway, this is not the first time I have gotten a code 33 (in fact it's the 3rd/4th) but it generally goes away for sometime after I clear it. But it is always accompanied by a park/neutral switch sensor. Again, the dealer informed me they didn't know why a park/neutral code would be being set off...and that they really had no idea what it was! Nor did they mention anything about 33 also having a timing meaning. :/ I am not happy. Oh well, I guess I will just replace the o2 sensor tommorow, change the fuel pump relay as well, and hope for the best.

BTW, my 95 SE 5s peed has 133 on the odo, and if ANYONE can describe to me in specifics what the h*ll a park/neutral switch is I would greatly appreciate it. As well as any steps you guys can reccomend to safely protect my engine from future problems!!!

TIA

[yellow_jacket]

The fuel pump relay does not control fuel pressure or pump speed. It simply turns the fuel pump on and off. Basically it either works or it doesn't. If the pump is going bad you would not have a rich condition either, you would actually have a lean condition especially on the top end. If you are running rich it could be O2 sensor, MAF, or coolant temp sensor. The park neutral switch just tells the car if it is in park/neutral and thus it is ok to start the car because it's not in gear. There is a chance it also tells Nissans that it is is in Drive and the computer may be looking for that. The FSM would give the causes for the light. As far as the timing being off, if the chain had stretched a lot it would be making a lot of noise. As long as you aren't burning a ton of oil your motor sounds ok. You just have a fuel managment problem(possibly a distributor problem, but most likely fuel). By the way, the fuel pressure regulator is what manages fuel pressure. It is on the end of the fuel rail and has a vacuum line atached to it.

[TimzSE]

Wow, thanks for the info!

Can you inform me how to diagnose FPR? When I check my plugs tommorow what should I look for? Carbon build-up?

[yellow_jacket]

To diagnose a fuel pressure regulator you need to have a fuel pressure gauge so that you can monitor your fuel pressure. I can't remember the exact pressure, but it should stay at about 35psi.