cant get rid of this miss.. help

[Four0Sport]

for the past few months i have had a slight miss at low rpms in my 5.0L. plugs are new, wires are new (twice), i cleaned the MAF, cleaned out my K&N cone filter, new MSD coils. I do have the annoying exhaust leak from the passenger cylinder bank. which has gottten worse, but i cant afford the down time of having the vehicle in the shop until i get my 93 back on the road. once in a while the CEL comes on for bank 2 02 sensor slow response but goes out soon after. tomorrow i am going to take the IAC valve off and clean it hoping its something simple thats giving me the miss. its driving me insane. could a leaky header give that much of a problem? thanks guys. any input is appreciated.

 

[Four0Sport]

just thought i would add that last night i moved the AIT sensor back to its stock position and not in the MAF adapter where it has been hoping that would cure the 100-300 rpm idle surge ive been getting after the truck bogs down in idle. but it didnt. I cant find my MAF cleaner to clean out the IAC, i dont wanna use TB cleaner.

 

[chriswells78]

Throwing any codes? IAC shouldn't cause a miss, just a bad idle condition. Maybe you have an injector going bad/clogged?

The exhaust leak is most likely a cracked header. It's common. I'll have one f/s in a couple weeks when I do my motor swap.

 

[tktrain]

A leaky exhaust header can cause a noticeable miss, especially under acceleration. I had a bad miss under acceleration on my 1998 5.0 Ex. I found that the EGR tube fitting had cracked loose on my FMS headers and that the accordion tube running from the header to the EGR valve had deteriorated and was also leaking. I had the fitting welded up and replaced the tube and my miss went away.

 

[Four0Sport]

no codes are thrown. under accelleration i do not have a miss, its only in idle, when i begin to accellerate, and when the vehicle is in park. in the mornings sometimes i hear a low whine coming from the engine bay when i put the truck into gear which led me to the IAC. which is drying on my sidewalk as we speak. hopefully that fixes it, but yeah.. i need to get my 99 and up cast manifolds put on asap. that exhaust leak is driving me insane.

 

[Four0Sport]

well I cleaned out the IAC with some electric parts cleaner. truck didnt whine and hiss when i left work tonight, then again it wasnt that cold. 75 degrees at 9pm in northern wv in october, strange. throttle isnt as hesitant as it has been, rpms didnt do a swan dive during idle. there is still a slight miss though, you can pop the hood and watch the motor shake slightly sporatically. hoping the bad pass side header leak is to blame.

 

[Four0Sport]

well the noise is back under the hood. kind of a low whine/vaccum sound. but still no check engine light. replace the IAC maybe? i hate buying parts that i dont need though. just curious but is there an easy, safe way to check for intake leaks other than the 'ol ether trick? thanks guys.

 

[Four0Sport]

so my egr tube was cracked all over the place, went up to ford, put a new one on. the annoying exhaust noise is gone, but im still having an idle problem. when either in park at idle, stopped in traffic at idle, or in park after revving the motor slightly as the vehicle comes back down to idle the vehicle will bog down to about 400 rpm for a couple secs, then the idle will surge up to between 600 and 750 then drop back down to normal 500. im not throwing any CELs, vehicle runs fine through town and on the interstate. the only other thing peculiar is sometimes when the vehicle has sat or is cold and i start it up and put it in gear i hear a noise similar to a vacuum or a woosh of air and the rpms raise slightly. if i put the vehicle in nuetral or back in park it goes away. i just realized ive posted in my own thread 6 times. wow. if anyone has any ideas they would be appreciated.


just thought id put down that i am running an air intake on the vehicle.