Random, intermittent idle problem

[Bozman]

My 1996 (4.0) D1 is having idle issues, sometimes.

Sometimes it starts right up and idles fine. Other times it has a very low and slow idle and will die when you give it gas. The idle is also heavy, meaning that it causes the car to rock back and forth. I let it sit for a few days or so, and the idle is fine sometimes and other times the problem continues. No real rhyme or reason.

While the poor idle is going on, there is also a loud sucking/hissing sound coming from the intake manifold. When I removed the air filter housing and MAF the hissing continues from within the plenum. When it is idling fine, the hissing does not exist.

Any thoughts before I start replacing things?

I was thinking maybe a clogged fuel filter, or a dying fuel pump, or a bad ground?

Thanks.

 

[Bozman]

Nobody?

 

[tex599]

My 97 was doing the same thing and about a 2 months later the fuel pump died. Would only do it after driving a distance. It was hesitant to restart and then once started required me to give it gas to keep it running. Not sure if it was 100% related to the fuel pump, but once I replaced the symptom has not returned.

 

[DeadHead86]

I had similar issues a while back. I replaced the fuel pump and problem went away.

 

[Hoot]

ok guys. thanks. i am going through the list also with a simialr problem. I blew out the MAF with cleaner, replacing plugs today. looking at VSS then fuel pump.