My truck *2000 5.2 dodge ram* warms up a little and then it idles waaay down and you can hear the engine sucking air from somewhere?? help?

 

IAC that sucking noise is sometimes normal when you first start truck but it sounds like you have a disconnected or bad vacum line.

 

Ya, it doesn't sound normal at all and never has done it before, so i think it might be its a very loud hiss when then hood is up, if you tap the gas, it will rev up real high then go back down, and when it warms up all the way, it stops, but seems like i'm using more gas also. tired of problems on this truck!

 

How many miles on that pre-cat O2 sensor? If it's over 80,000 miles, replace it.

Or try this: When the symptom appears, rev the engine (trans in neutral or park) to 1500-2000RPM and hold it there for about 15 seconds. If that clears it up and you don't see the problem until the engine cools again, it's almost certainly the pre-cat oxygen sensor.

 

that sounds exactly like what is going on...manual tranny tho....and the cat converters have been taken off. I have 97,000 on this ride

 

97k is time for an oxygen sensor even if it hasn't failed. I'd give that a try since it's needed anyway.

I'd be willing to be that your manual trans has a neutral in it.

 

haha....ya it's got a neutral. which o2 sensor is it u think? isnt there like 3 of em?

 

I suppose the number of sensors depends upon the factory exhaust configuration, the locale for which it was built, and the whims of whoever's fooled with it in the past. There will be two sensors per catalytic converter, one in front, one behind.

That said, we'd be looking at the sensor or sensors in the original pre-cat position(s). The ones that go in front of the cats are used for timing and mixture control, while those behind the cats are there just to indicate whether or not the cat is working and throw codes if not.