I just bought an Autotap. I already knew I had a misfire somewhere, and it just showed me that it was cyl #4. Change the coil, no sweat. (I knew it was the coil, because previously the misfire was on cyl #3, and I swapped positions of the coils.) However, I noticed somthing else while driving. There's a catagory called INTAKE RUNNER MANIFOLD CONTROL FAULT. At idle or part throttle it reads NO. But when I gas it, it changes to YES. Here's the question: Is that a problem, or could it be lag time b/w the order for the seconday valves to open and when they actually open? Also, my TPS reads 19% @ idle and 93.4% WOT. I thought this was bad until I put the scanner on my buddy's 97 F-150 5.4L and his is at 16% @ idle and 92% @ WOT. Is this a sign that they're starting to go bad, or just a offset? (Autotap says it should be at 0% idle and 100% WOT. By the way AUTOTAP is the next best thing since canned beer.

 

The percent at idle and wide open will be differant for every veh. This is the % of avalable TPS voltage 0% being no volts and 100% being 5 volts. Normal idle tps voltage is abot .9 volts so 18% to 19% is right on' and wide open is always less than 5 volts so again 92% is right on. mine idles at 18.80% and wide open is 92.90%
I have never looked at intake runner control but from what I understand of it's function it sounds as though it is operating properly. It is supposd to make the intake runners longer at slow speeds to increase the torque output of the engine. then at higher Rpms it shortens the runners. If you don't have a code I would think that it is operating properly. I have read wher if you change to amanifold without runner control you have to remove the motor from the old manifold and connect it so that the computer thinks it is there.
I use my auto tap for tuning datta, so I only log the necessary perameters that I am looking for as the more things you log the slower the function. It shure is a fun tool to have though, you can really understand what acomputer controlled engine is doing.

 

I was wrong. Not the coil. I believe that I have burned rings on #4 cyl. Tell me if this sounds right.... When I pulled the plug, it had oil around the threads and some crunk between the electrode. Damn, I have another motor, I'm just not ready to do the install. I put a new plug in and cleared the codes, so we'll so how long it lasts. There's no more surging at a even speed anymore, and the idle has smoothed out drastically.