I have a rough idle problem, and have checked pretty much everything. I changed cap/rotor, wires, plugs, and ohm tested injectors. I found a crack in one of the vaccuum hoses that goes from the air intake collector to this black football-sized container under the battery (whats that for??). So next week when I have some time off, I plan on changing all the vaccuum hoses, and also cleaning the TB and IACV valve since I heard those can also cause idle problems.

I want to change all the vaccuum hoses. I think its about time, since most of them are hard, and my car is about 16 years old. What sizes are the hoses, and how much do I need? Can somone give me a rough estimate, like 3ft. of 3x8 hose, or something like that.

I have already ordered the pcv to rear crankcase hose, since that one is different sizes on each end. Thanks in advance for everybody's help..

 

- Cold, hot or both? TPS=cold, O2=hot. Both=none of those.

- Measure MAF.

- New cap may be doa... dead on arrival.

- Check voltage at ECU. Groundings. Connectors cleanup...

 

If you can afford it, replace all the injectors. Even thought they have the correct resistance, they have a filter screen that gets plugged up, and their are o-rings that leak fuel into the cylinder. As a cheap way out you can remove them and clean their screens and buy a all new seals.

 

The idle will go to like 5500rpm, and then go back up to 7000 at a stop light while in Drive. No codes at ECU, cleaned ground connectors already, and ohm tested MAF. It does this both, when the car is cold or hot. I am planning on changing the O2 sensor anyways. All the injectors were changed at 50k with OEM Nissan ones.

I remember Wiking saying that all vaccuum hoses should be changed at 100k. My car now has 98k. Is there a way that I can find out how much I need to buy? Should I get them from local parts store that sell hoses by foot, or get from Nissan?? and should I also change all those coolant hoses that go to the Air intake collector??

 

- ECU is a lol lottery machine: first need to buy a ticket...

- There are lots too many connectors...try to find them all.

- Was that 7000/5500rpm a typo or actual? Thats not question of idle... U must mean 550...

- Ohm tested MAF? ...but did u check the gradual voltage rise?

- The need for hose replacement can be viewed: take out the engine attached (=typically hot end) hoses. View with good light, press and look for brittles. I just cut off half inch... Bend hoses and look for cracks: if found, replacement keeps towing company bankrupt.

- Do the IACV cleanup: infinidecimally small leak may cause problems. Use liquid sealant if necessary. Even installing the feed tube back may be cause a leak; it may not seat at first 100%.

- If money problems [=too much] go to stealer$hip. Or send a boatload to me and then autozone...


e-dit
Check also Nissan TSB NTB94-085.pdf; idle fluctuation due to filter.
TSB's see for http://maxima.theowensfamily.com/tsb

 

yeah, I hope that was a typo.

 

yes it was a typo, my bad. i meant 700rpm down to 550.
so has anyone changed their vaccuum hoses?

 

Idling between 700 and 550 is very normal. You might want to bump your idle speed in park up to 800.

I've replaced all my vacuum lines a few years back, so I don't know lengths or sizes, but make sure they fit fairly tightly. They are all metric, but I don't they they are all whole numbers.

 

I would guesstimate that I used about 6 ft of 3/8"