I have a 1999 Dodge Ram 1500 with the 5.9L engine and about 101,000 miles. Just recently it started having some running problems that have seemed to slowly get worse. First it started a hissing sound like it was sucking for air. The truck was also idling rough with a slight loss in power. Thought it was the IAC but it was a bad air intake gasket. The truck ran great for about 2 days. One hot afternoon I tried to start the truck, it started but stalled about 3 seconds later. I tried a few times and same thing over and over. Figured it was maybe related to the IAC again so unplugged that and the truck started normal. This worked for a few days if the truck would stall after starting. Today I went to start it this afternoon and nothing seems to be working. I was able to get it idling for about 10 secs but stalled, even with pressure on the throttle. Talked to a local mechanic and he thinks its a vacuum leak. Does this sound correct? His other theory was a fuel injector leak.

The symptoms:
1)The truck seems to start normal after sitting over night. Just in warm/hot weather or after driving and letting it sit for 30mins it has a heard time.
2)More often than not, If I unplug the IAC, the truck starts and stays running.
3)Engine will still stall if I try to slightly rev it right after startup.

Any help would be greatly appreciated. Just has not bee my week with vehicles. Brand new Jeep Wrangler, 11,000 miles in shop for warranty work. So need to try and keep this truck running seeing as right now its my backup.

 

Read the plenum sticky and make sure the cat is not clogged. Could be other things , but you have to start with that.