02' 4.7 w/ 166k, my idle has been fluctuating from almost stalling to about 1500 RPM's. I recently cleaned the TB and changed the IAC and TPS. No differance. i have done a visual check for any vacuum leaks and I didn't see anything, but that's not saying there isn't one. Any other ideas. If it helps, this started when I had a cracked head putting coolant onto two of the cylinders that has since been repaired. Not sure if related though.

 

How long since you changed the plugs? PCV valve?


SJ03

 

The plugs and pcv valve were changed when I changed the head last weekend. I have also changed numerous other thing such as some coil packs and some injectors. The surging idle was happening before I did the top end over haul and I was hoping the over haul would have fixed it. The truck runs like a champ now but I just have to get the idle straight before it kills my tranny.

 

Are you getting any codes?

 

0 codes. I'm going to spray some ether or WD on the vacuum lines later to see if a line or rubber is cracked.

 

I'm betting vacuum leak, although you may want to take a good look at your plug wires...

 

Well I checked all of my vacuum lines first with a spray bottle filled with soap and water and then later on with ether. I didn't see anything or hear anything while checking them that would make me think I had a leak. And about the plug wires.... The 4.7 has coil over plugs, no wires. I have replaced EVERY coil and plug and still does the same thing.

 

Winner winner chicken dinner..... After weeks of racking my noggin, it seems as if the MAP sensor was the problem. I changed it last night but never started the engine because it started raining. Went this morning to make groceries and I had to make sure I was in the right truck. The engine ran awesome, idle was perfect. Thanks to everyone for all the help.