engine hard to start when hot

[Jack2048]

What kind of plug is the TR55?

Not sure what you are asking.

 

[alldodge]

Not sure what you are asking.

Your plug pic shows TR55 and Power, so just wondered who makes them?

 

[Jack2048]

NGK

 

[Scott Danforth]

I pulled this. Not sure how to test this. The sensor reads 10.7 ohms. But did not change reading when I ran a hair drier over it. Only went down to 9.8 Ohms after ten minutes in the freezer.

you connect a pwm power source to it, and depending on what the voltage is, the IAC opens to that point (or closes to that point) its a small stepper motor that opens and closes a throttle plate bypass

 

[Jack2048]

its a small stepper motor

Well, that seems obvious now, probably tired when I looked at it last night.

No PWM Supply here, but, the IAC opens when given +12v.
The Air Charge Temperature Sensor responds appropriately.

I restarted the engine, hose from the fuel pressure regulator to the plenum has good vacuum and does not appear to have any leaks. Nothing coming out of the regulator.

 

[alldodge]

All the sensors controlled by the ECM use 5V, applying 12V can damage them.

Nothing coming out of the regulator.

Nothing should come out of it, vacuum controls the pressure increase. Even though the ETC responded appropriately do wonder if the engine thinks is cold and supplies more fuel. Need a scanner to see what the ECM is seeing

 

[Jack2048]

All the sensors controlled by the ECM use 5V,

Ok, good to know!

applying 12V can damage them.

This was not a sensor but the stepper motor. To determine polarity I was looking at the signal on the connector which read 14.5v.

Nothing should come out of it, vacuum controls the pressure increase.

Right, agreed. But I was reading somewhere in one of the manuals to which I was pointed, that the regulator should be checked in this manner.

Water temp sensor ok.

 

[alldodge]

This is the wiring for the IAC on a Merc motor and so far as I understand, same parts are used by VP

 

[Jack2048]

I unbolted the IAC and covered the opening. Running the engine, I did not see any movement on the valve. I don't know if that helps.

 

[alldodge]

I unbolted the IAC and covered the opening. Running the engine, I did not see any movement on the valve. I don't know if that helps.

That is weird, the motor should have died if all the air was closed off from the IAC port

 

[Jack2048]

That is weird, the motor should have died if all the air was closed off from the IAC port

Yes, at the same time the computer had the valve closed while running. If attached, it would be the same as my tape covering the holes. Wouldn't it?

After cleaning the IAC, there was dirt in the metal filter, the uneven idle seems to have gotten better. I want to re-check this when the engine is cold, in case it was just a byproduct of the engine being warm from when I ran it earlier in the day.

Next to check is the PCV.

 

[alldodge]

same as my tape covering the holes.

Maybe, if you just covered the hole the IAC came out of then no

 

[Jammer864]

There are 2 temp sensors on that engine. One for the gauge on the dash and the other for the computer to tell it how hot the engine is. Using the factory manual for temps vs volts (page 3-15), check the one driving the computer, Also I couldnt tell but have you had the injectors flow tested? Possibly one or more are leaking?

 

[Jammer864]

from a former Ford mechanic that knows the Ford FI fuel system......"when voltage is low, the computer interprets that as being cold, so more gas is added to help start. Make sure battery connections are clean and tight, and check cranking voltage at the starter. The computer may think its cold out when in reality its only a poor connection." Just a thought.......