I have a 98 1500 5.9l 360 and when its warm outside and the truck is idling sometimes it will idle rough kind of a hissing sound coming from the front of the truck and the rpms drop. Sometimes it even dies. It doesn't do it much when its cold but when its warm it will do it bout every other day or so. A/C doesn't work, the fuse keeps blowing so I don't know if that is the cause or not. It does this rough idling when the heater is on and off and if the A/C fan is on or off. Thanks to anyone who can help.

 

sounds like a vacuum leak...also check your intake tube for cracks or holes missing

 

Mine does this exact same thing, 1998 1500 5.9 4x4 extended cab. It is not a vac leak as it only does it sometimes or whenever I leave it running to warm up, the rpm drops slightly & then the iac opens up which is the hissing while it stumbles around some. Usally it will correct it's self after a few mins or if I goose it a bit a few times it will smooth out & the iac closes to normal again. Although I do not think it is the problem I got a fuel pressure gauge setup today & am going to put it on tomorrow & see if it will show a pressure drop when the truck is acting up. I have done a full tune up & the TPS is at .68v but I have not yet pulled the TB to clean everything out yet. I say it is not a vac leak as the last time it was doing it I hosed every vac line, connection, TB, intake everywhere with carb cleaner with no change but if I hit the air filter with carb cleaner when it is doing it, it smoothes out for a second. It is acting like it is leaning out but usally does it when it is cold or warming up & is not in closed loop yet so the fuel pressure check is just a theory. I have 150k miles on it & all is well except for this.

Any ideas where to look next guys?
Thanks

 

I would look at the O2 sensor before the cat. My truck ran very rough in closed loop abd did not throw any codes at all. I changed the before cat O2 and itfixed the entire problem. I would also clean the TB without even thinking about it. I did mine and just bought a newIAC runs really good now! The chart below helped me see what sensors work when.




http://www.bionicdodge.com/Download/...d%20Tricks.pdf

 

Lots of good info on that site, thanks!

 

How much do those O2 sensors run nowadays, and where'd yah get it?

 

What is the bearing in the very middle of the picture that allows the tires to turn while in 4WD called?




And, where is this ground wire (just above engine oil cap)supposed to hooked up at? Just noticed it was hanging loose.



Thanks for all your help, BTW I found the 02 sensor it cost bout $50 for the one with 4 wires coming from it like mine.

 

First pic ... U-joint.

Second ... if that's a flat insulated strap ... it runs down behind the motor and bolts to the back of the block ... right around the corner from the exhaust manifold ... and down a bit ... but still above the starter.

 

What's the part no for that O2 sensor and where did you buy it? My truck does the same thing during warm up it will start to idle alittle rough then smooth out after about a minute. I'm hesitant on yanking the the TB to clean it because I want one of the 50mm Fastman ones.

 

The website in your post states " the file is damaged and could not be repaired".