Alright, just looking for a little help here so thanks in advance. I have a 1999 Ford F-150 with a 4.2 V6 engine. Standard of course. And like most people on this forum..I have no tach. I have purchases one from summitracing. It is nice, and it was at a good price too. The instructions it came with are well worthless. Basicly red goes to all time hot. Yellow to accesory hot and black to ground. The green goes to the "ignition coil 12 volt negative connection." So I have done some searching..and I have pretty much found that that certain wire is suppose to be the white with a pink line on top of the ignition coil. I have already tapped into it, and no luck. So I moved to the next wire that goes into the ignition coil. And no luck there. I have tried the last one, and still no luck. The only other one that is left, is the one that is the actual 12volt hot wire that feeds the coil. I have read of people going just under the dash and were able to find the pink wire with white line. I have not looked under the dash yet, but I have looked on the wire cluster that is next to the brake booster on the driver side engine compartment. Needless to say, that I have not found that certain wire there. I tapped into the only half *** looking white with pink wire that is there..and no luck. Now when I tapped into the dark blue with white strip wire ontop of the coil pack, I did get a reading. And when you press on the gas, the tach does read, but then it just makes a drop all the way down to zero and will stay there until you release the gas. The it jumps back up to 500 rpms. Which I know can't be right. Or so I think. Then when you press the gas again, it climbs to about 800-900 then drops down to zero. It does the same when I tap into the other two wires ontop of the coil. I am just confused and have no idea of what to do. I guess I could go on a search and destroy mission under the dash for the white with pink wire, but if I can't find it..then what. On a Chilton Manuel that I have..it says that on the ECM Module it should have the white with pink wire comming out for a tach. Problem is..I can't find no damn wire. Am I just looking for it in the wrong place? My other last resort is calling summit racing tomorrow and see what they say. But I am thinking that they are going to tell me that my vehicle can't have an aftermarket tach installed. I just know how customer service people work sometimes. Instead of spending time trying to help you, they say it can't be done. One way or the other, I am going to get this done, and maybe I can later post on here how I did it. Thanks for the help, and every little bit helps.

JP