hmm so could this have something to do with the fact that my tach works only 10% of the time. Most of the time it stays inbetween the 2 and 3 and doesnt move at all. Every now and then it will start moving and work fine for a few days then all of a sudden go back to where it was and stay there. I thought it might have just been sticky or somehting but i actually watched it go from a low idle up to the point inbetween the 2 and 3 and stay there when my engine did not rev. Also my temp guage stays at the bottom all the time. Does this sound like a problem that would need to get fixed before it causes more damage? or just something that is no big deal other than my tach not working

 

now that you say that, you probably have a large wiring issue somewhere, or the computer is junk. slight possibility that the temp sender is bad, but it wouldn't just stay dead, normally. bad temp senders will usually only go up a little tiny bit.

start looking at your wiring. more than likely the rubber grommet that the wiring passes through in the firewall has dryed out, rotted, and somehow allowed the wires to cut themselves against the sharp lip the grommet is protecting. it happened on my ex-girl's bonneville. 1 single black wire shorted from the firewall all the way through the dash to the computer because it was rubbing on metal in a split in the grommet, causing the car to sputter and die totally randomly.

 

FYI...IDM = Ignition Diagnostic Monitor signal from the ICM (Ignition control Module)...shared between the Tach and the ECM...check the diagram below....first wire RH side connector.......



Either
1. you have a wiring/connector problem at/between the ICM and ECM......
2. the ICM is kaput,
3. or the ECM is 10-7.....
Since you're also having problems with the tach, ICM connector problems or #2 are good candidates........my 2¢.

 

very informative, thanks for picking up my slack. i'm lazy.

 

temp sendors seem to go alot in fords, something like 40 bucks to replace, mine stays dead without motion but i hot wired the sensor to the battery once and the gauge still works so i kno its the sendor

Quick question, my check engine is in constant on and off, when ever i am not at idle, can i still test it ona diagnostic if it isnt always on (does the computer have a memory)???

 

yes it has a memory

 

what would code 94 relate to? honestly have no idea what its talking about

 

Temp sender is not connected to the ECM.....also make sure you replace it with the correct color coded sender (usually green center insulator for Mustangs)....

Yep....there are three types of codes in the EEC-IV system....(O) = On demand, (M) = Memory codes and (R) = Engine Running codes.

 

Alright guys sorry to bother you again but I still have this problem and first semester is just ending so i wont have auto tech any more at school so working on my car is going to be a bit harder. I havent quite figured out this problem but i have more info about it. Before i didnt notice a difference in performance when the check engine light came on but now i have noticed that when im at a red light it idles rougher and shakes more. And accelerating doesnt seem as quick and smooth. Also i havent noticed any connection between the check engine light and the tach working only 40% of the time. From what im hearing theres somethign wrong with my coils? is that the things that the spark plugs connect to? are they cheap and should i replace those? (i just started work in an auto parts store so i will be able to get parts cheaper) .