View Full Version : What Is This From?

01-23-2007, 09:19 PM
Hi I'm a newbie here, but not to cars I have an 87 5.0 that I built and have always worked on cars be it mine or my brothers fathers or who ever. I just got my sc about a month ago since I have installed a trango shift kit the hp model. The rest is stock it is a 90 and it is whit I will try to post some pics this weekend if weather isn't sloppy.

But here is my question my tach is working intermitently and sometime the car gets an extreme rolling idle. Also it sometime cuts off and is always hard to start. these things usually happen after the tach cutoff or on. From my reseach I have found that this is usually due to a faulty ingnition model. So, I bought a new motorcraft one from spinning wheels. I just installed it today and while I haven't driven it enough to know about the stalling and rolling idle the tach is still not working and it is still hard to start. Does anyone have any other thoughts as to what tghis could be? I was thinking maybe a leaking injector but not sure. any insight would be much appreciated

01-23-2007, 09:39 PM
Should have asked first. Sounds like a cam position sensor. One of the jobs of that sensor tells the EEC the info it needs to know which coil to fire to start the engine. When it's failing, the EEC has a "give it a shot" strategy, where if it doesn't get a good cam signal, it'll guess when the #1 cylinder is on TDC for the compression stroke. So it fires the plug. If it doesn't work the first time, the next time you turn the key off and back on again, the computer tries a different time. Usually within 5 or 6 tries with a bad cam sensor you'll get the engine to start and it'll run.

To test, you can pull the connector of the cam sensor and see if the behavior changes. My guess is that it won't change other than the tach will completely stop working and it'll always be a challenge to start.

since it's been pretty intermittant, I'd check the condition of the connector and it's wires closely.

01-23-2007, 09:47 PM
thanks that make alot of sense I'll check it tomorrow and see it it makes a difference.

01-23-2007, 10:19 PM
It will. Aside from the wiring, those are the only two parts that come to mind that will directly affect your tach and idle/stalling.