Hey guys!
i have a 2000 5 speed max and i'm a few issues with it. In the winter when it was 32 degrees out my car ran fine, no bouncing of the rpms what so ever. Then a 60 degree day came and it was fine when it was cold, fine on the highway then the rpms began bouncing at traffic lights, but would soon go away once i accelerated. Now today it was 80 degrees and all hell broke loose. It was fine when i first started it in the morning then at traffic like my rpms were bouncing like crazy between 200rpms to 700rpms and stalled several time. When i rev the engine in neutral it revs perfectly once it settles back down to idle it begins bouncing again. I turned on the AC and the rpms went up to about 700 for 5 minutes then all of a sudden started bouncing again. I then drove with the AC on and it felt like the car weighed 10,000lb it was accelerating so slow at WOT. I went to class came back drove the car home (it was a 60 degree night) then once in my driveway it started doing it again and it began accelerating poorly again. Basically it runs perfect when the weather is 40 degrees or lower. The hotter the weather the more the engine shakes. Only CEL is P0420 for an o2 sensor but i think that shouldn't affect my performance since it was on even before i had this problem.
(MAF and IAVC were changed a year ago, disconnected maf issue still occurs)
Any advice would be perfect thanks!

 

sounds like a Knock Sensor, but fix the o2 first.

search here and 4th gen forums for Knock sensor. See if that resonates with your issues. You will have a lot of reading to do.

 

i dont think its the knock sensor because my symptoms are much more sever. Idle bouncing between 200rpms to 700rpms and acceleration is terrible at Wot. A bad knock sensor would make my engine shake but not shake that severely, and yes it would affect my acceleration but again not that severely. I have a bad knock sensor in my 97 maxima but its not a huge issue i notice as far as performance wise.. can it be spark plugs? is there more stress on plugs when hot?

 

I'm almost 99% sure it's an electrical issue.

Have you tested your IAT (Intake air temp) or CTS (coolant temp sensor)?

 

hey Tunermaxima3000 thanks for all the advice.. i just changed the PCV on my way to school because i searched that someone here had the same problem and the PCV solved it. I drove the car for 20 minutes and let it idle for 20 minutes and all seemed well. I dont know if its the weather again though. It was a cool rainy day today about 50 degrees. The only way ill find out if this works is when its hot out like 70 or 80 degrees. If it still does this im going to change the CTS, if it continues then ill rip apart the manifold and change the knock sensor and the spark plugs. Hopefully all this would fix the problem.

 

you replaced IACV ? with new one or junk yard item ? seems to me it's you IACV

 

After only reading first first couple sentences I thought knock sensor.

 

i had the p0505 code a while back but i replaced it with a brand new one and reset the battery. I never got that code again and instead of my idle being at 900 its now at 700 and it doesn't fluctuate like it used too, so i dont think its my IACV. From what i heard our ECUs know if our IACV goes out before we even notice.. its just that some of dont get the codes checked and it fries the ecu. But i caught mine on time. My car runs 100% fine in cool weather but once hot and put under stress (AC on) it idles really bad. One thing that caught my attention was that while i was accelerating in first gear when it was hot i heard a ticking noise from the engine (similar to when you have low pressure in your engine and start in 4th gear.. that noise). So i thought it had to do with oil pressure in the engine. The car starts easier with the replaced PCV and isnt as loud as it used to be..