Idle irregularities every now and then

[abrush]

I have yet to figure this one out but it makes it hard when my 88 B2 with a 1994 4.0 engine doesn't act up all the time. Every now and then, and it seems to happen when the engine isn't completely warmed to full temperature, the B2 kind of acts like it is going into convulsions. The idle will rise and drop to the point that I can see the front of the engine rocking back and forth while sitting in the driver's seat. It only does this while stopped such as sitting in park or at a stoplight in drive with the foot on the brake. The minute I hit the gas to take off it quits and runs great. Then I will get to the next stop light and stop and it will idle perfect. I want to say it will idle irregularly 1/4 of the time. Does anyone know why it would be doing this?

 

[crazywhiteboy]

im havin somewhat of similar problems with my 97 4.0...like today, i was out playing in the snow, and after i was done climbing a steep icy hill i shut off my ignition, and my engine tryed to stay running. then it jumped to probably around 6500rpms. but my keys were out and ignition was off. so i opened my hood asap and pulled the power cable off the battery. now when i start it, it idles at 3000. anyone have any clue about what happened and what i can do to fix it? thanks!

 

[Capt Jay]

Sounds like a vacuum leak.

 

[reno]

Vacuum leak or the MAF going, that is how mine started out (MAF), even though i did have a vacuum leak at first. Start with the Vacuum leak first. You pulling any codes yet?