oil pressure

[um_fan]

I've had my '02TB for about 2 month now and never really notice my oil pressure gauge untill I got a check engine light over the weekend. I got a P0440 error, and reseted that code (wife left the gas cap half open and hope that was the issue).
Then I got a P0305(?) Code (o2 sensor). My question, my oil pressure jumps to above 40 when I accelerate and keep a cruising speed of about 60-65 mph. Is this normal :confused:
Also, where is the o2 sensor located? I'll try to replace that myself, right now I'm getting about 18-19 mpg (mix: city & highway)
Thanks

[ylab]

That oil pressure sounds about right, my '02 idles with 40psi of pressure. (Higher when the oil is overnight cold) The pressure will rise with engine speed and highway cruise is around 60-65 psi.....if you watch the switch accelerating or reving the engine, at some point it stops rising when the pressure relief valve kicks in.

As far as the O2 sensors, there should be two. One towards the bottom of the exhaust manifold/header and another after the cat....but P0305 is a misfire detected on cylinder #5 and not an O2 sensor failure. (Note that code really means that the #5 cylinder isn't burning the fuel correctly, not necessarily a bad plug/coil as a plugged injector could also cause that error). If a mis-fire code, even if intermittent, remains for a prolonged period of time the PCM may deactivate the injector on that cylinder to prevent converter damage and you WILL notice reduced power/rough idle/etc. - In other words, fix it pronto!

[um_fan]

That oil pressure sounds about right, my '02 idles with 40psi of pressure. (Higher when the oil is overnight cold) The pressure will rise with engine speed and highway cruise is around 60-65 psi.....if you watch the switch accelerating or reving the engine, at some point it stops rising when the pressure relief valve kicks in.

As far as the O2 sensors, there should be two. One towards the bottom of the exhaust manifold/header and another after the cat....but P0305 is a misfire detected on cylinder #5 and not an O2 sensor failure. (Note that code really means that the #5 cylinder isn't burning the fuel correctly, not necessarily a bad plug/coil as a plugged injector could also cause that error). If a mis-fire code, even if intermittent, remains for a prolonged period of time the PCM may deactivate the injector on that cylinder to prevent converter damage and you WILL notice reduced power/rough idle/etc. - In other words, fix it pronto!
I haven't notice any loss in power or rough idle at all, I could be wrong with the code. I did look it up and it said o2 sensor. Right now I have no engine light now. I'll run the scanner again today and take it to the dealer tomorrow just to make sure. But the car is running fine right now...

[gabe]

i have a 05 envoy and the oil gauge starts a 40psi and it hardly moves. my dodge starts at 20psi and goes way up it moves alot. is this normal for gmc oil gauges to move very little or should i take it in to the dealer. thanks :confused:

[ylab]

Gabe, the stated oil pressures probably doesn't apply to your Denali, which has the 5.3L V8 and not the standard inline 6. In the I6 the oil needs to reach and protect a greater number of moving parts and travel farther distances than in your V8. The vehicles I've owned with Chevy V8s usually held between 32-40psi of pressure and they used to be pretty steady.

Anyone with a 5.3L able to confirm for Gabe that its oil pressure still behaves the same?

[Dacomputernerd]

Yep, with my 05' 5.3 the pressure stays pretty constant :yes:

[um_fan]

I just ran a new scan right now and got "No Code" :confused:
Before I had 2 error code...anyone with ideas...

[sweaburgbull]

I was reading your earlier reply with respect to the pressure relief valve. Is this something that can stick or fail? I noticed today that my oil pressure guage is "off the charts". Even when the truck is off, the guage reads way over to the right. I'm not sure if that means that the guage is faulty or if my pressure is actually high. If it is my pressure reflief valve, is this something I can change or should I bring it into the shop to have it changed out? Lastly, I just had the cat. converter swapped out on it. I don't think it is related but I thought I'd throw it in...

Sweaburgbull

[Super 88]

I was reading your earlier reply with respect to the pressure relief valve. Is this something that can stick or fail? I noticed today that my oil pressure guage is "off the charts". Even when the truck is off, the guage reads way over to the right. I'm not sure if that means that the guage is faulty or if my pressure is actually high. If it is my pressure reflief valve, is this something I can change or should I bring it into the shop to have it changed out? Lastly, I just had the cat. converter swapped out on it. I don't think it is related but I thought I'd throw it in...

Sweaburgbull

Sounds to me like a bad gauge based on you said the gauge is way over to the right even when the truck is off. Obviously when the engine isn't running you have no oil pressure.
There is a guy on ebay that rebuilds these gauges. I've never had to replace one, but IIRC most people have said the dealership will want to replace the whole instrument cluster which is of course extremely expensive.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280142887467

[AbsoluteZero]

....but P0305 is a misfire detected on cylinder #5 and not an O2 sensor failure. (Note that code really means that the #5 cylinder isn't burning the fuel correctly, not necessarily a bad plug/coil as a plugged injector could also cause that error). If a mis-fire code, even if intermittent, remains for a prolonged period of time the PCM may deactivate the injector on that cylinder to prevent converter damage and you WILL notice reduced power/rough idle/etc. - In other words, fix it pronto!

I recall there was a TSB in the recent past dealing with water getting past the hood seal and accumulating in one of the plug well which could cause a misfire.