Hi all. My wife purchased this 96 Jimmy from auction. The 4.3l vortec engine ran rough but strong. I just finished replacing plugs, wires, rotor button, distributor cap and air filter. When I start it there is something way wrong. It surges to about 3k rpm for a couple of seconds and then drops to about 500 rpm and runs really rough for a couple of seconds,then it repeats the surge to 3k and drop to 500 a couple of more times then it quits. I checked and got code P0108, I replaced the MAP sensor, double checked the plug wires and even put the old distributor cap and rotor back. What did I foul up?

 

Sounds like your IAC valve is sticking. The IAC valve is in the side of the throttle body.

 

Thanks for your reply. I cleaned the EGR valve today and I'll get tot the IAC valve in the next day or two.

Question: Is it possible that a clogged fuel filter or a clogged catalytic converter could be causing this problem? The catalytic converter rattles. The tank was very near empty, I've since added a gallon or two, but I wonder if the filter clogged up when it hit bottom.

 

I do not believe a clogged cat or fuel filter would cause surging like that.

 

I think I found what I fouled up. While putting the IAC valve back after cleaning it I noticed a part that seemed to be out of place. I don't the name of the part but it is about 2" round, black plastic on the other end of the piece of tubing that has the pcv valve. I pushed it back in to it's hole and now the problem is gone. I even went so far as to pull it back out of the hole and the problem reappeared. I thought all along that I knocked something out of place because the problem appeared so suddenly. This car is new to me and it's not so easy to work on. Any idea on the name of the part?

Thanks for all tips/answers!

 

We discussed this a week or so ago. There really isn't a name for it per-say. It is just a fitting that comes with the lower intake manifold. I believe it twists to lock into place.

 

sounds like it was a vacuum leak.

 

Yes, I can see a twist and lock was the plan. However I can see where the lock tabs are gone now. Hope it stays in place.