ok here we go, i went to check the map sensor, haynes manual says the connector should between 4-6 volts with key on no vacuum and not connected, it read 4.9(so far so good) then i plugged it in and the book said it should read 5.0 volts(voltage varying type) it only read 2.4 volts, is this thing bad? Also my symptoms were high idle, it starts about 1000 rpm then slowly goes to about 1500 rpm but it tries to kick down but goes right back up, i replaced tps sensor check IAC for volts, all tested good.
Help me with this headache!@@@ thanks for all your help@!

 

No. The book is wrong. 2.5 Volts is the correct reading for when it is plugged in. I thought the same thing, and so bought a new sensor thinking that was throwing off my mass air conversion, but I got the exact same reading (2.5 V) with the new sensor. I then found in another book that the reading should be 2.5V.

 

where else do i look?

 

Look for what?

 

When you replaced the TPS, did you make sure that it's below 0.99V at idle? If it's anything over 0.99, you'll get that same behavior. After adjusting it, snap the throttle repeatedly and make sure that it's always going to the correct voltage or less and adjust as needed.

Have you cleaned out your IAC? Just because the voltage is correct doesn't mean that it's not sticking; it just means that it's being cycled correctly. Take it off and clean it out really well with carb cleaner.

And, BTW, the Ford MAP sensors work on frequency rather than voltage, and although the voltage will probably give you your answer, testing the frequency will give you the best answer. Except I don't remember what the frequency is supposed to be near...

 

85-90ish Ford Fuel injection had voltage varying MAP sensors, after that they were Frequency varying type. So you you are both correct. The voltage varying type are much easier to test. The frequency type must have a oscilliscope to test it. ( or a least a Digital meter that has a RPM function.

I agree with IAC theory, clean it out and make sure you do not have any vacuum leaks.

 

I think with either type, voltage varying or frequency varying, with the vehicle off (no vacuum), the signal wire should show 2.5 volts, and will change with vacuum if it is a voltage varying type. You can test the frequency varying type with a tachometer set on the 6 cylinder scale. I don't know exactly what frequencies, but a repair manual should have a table. I definitely would clean the IAC first off, as MAP sensors rarely go bad.

 

ok, i will check the tps sensor for 0.99 volts and i did clean the iac real good, it runs at 1500 rpm then down to 1000 rpm then back up, i will keep you guys posted... thanks for all your help!!!!