codes, now a no start

[vegasfj40]

Also, how does it idle when cold?

 

[Alan Jones]

It is running rich until it warms up, then leans out. What temp sensor should i check

 

[Alan Jones]

When cold, idle jumps from 800 to 400 and bounces back and forth until warm. Once warm, runs like a champ.

 

[Alan Jones]

From my understanding the o2 sensors should be on hold until normal temp is reached.

 

[vegasfj40]

You can check the water temp switch.

 

[incogrhino]

I have most the same codes going in my new to me 95'. Only 1 o2 sensor in the system. Mine starts and runs fine. Its -13 at night and fires right up.

 

[Alan Jones]

Just ran some obd diagnostics and here are some measurements. Short term fuel trim 0.0, long term fuel trim 19.5, TP% 8.2, B1S1 0.035, B1S2 0.125, Fuel sys 1 OL_Fault. Does any of this help?

Coolant temp sensor did not help...

 

[Alan Jones]

So I just started it in the cold and is started normal for a second, with the rpms kicking up to about 1500. It then quickly dropped rpms, and did the jumping gauge again. I am wondering if this is an indication that the IAC works instantaneously but is not holding the TB open long enough to warm. Does anyone out there think it is likely an IAC issue or another sensor kicking the IAC out of gear? I know these can be pesky to diagnose, but ANY help is appreciated. I have time this afternoon/evening to check whatever you guys suggest. Thanks again!

 

[Alan Jones]

Is there a simple way to test the IAC, or is it a matter of taking the unit off and following the FSM diagnosis...

 

[Alan Jones]

I am now at a no start condition. I have checked for fuel pressure -good- and checked all sensor connections -good-. It will try to fire but only for a millisecond. I cannot get enough fire to register any codes. I pulled the negative battery cable over night and reconnected this morning and no change. If I had FULL insurance on her today I would consider staging her death. H. E. L. P. I still believe a faulty sensor is to blame somewhere...

 

[Rifleman]

When cold the front sensor will read 0.0 to about 0.3 and when warm it stays near a 1.0 reading.

In general, a 0-volt or 5-volt reading indicates a problem with O2 sensors. The 1.25 volts or 3.75 volts is considered normal with 2.5 volts considered optimal. When you checked the sensor voltage were they switching back and forth between rich and lean in closed loop when the motor got up to operating temp? Check this link out, it might help you trouble shoot your sensors voltage readings.
Vf1 voltage

 

[Alan Jones]

Would faulty o2 sensor readings lead to poor idle only a low temp and eventually a no start condition. I am pretty good with a wrench and a lot of tools but understanding the intricate connections between all the sensors is not my strength.

 

[Alan Jones]

Alright, I pulled the IAC again to test, based on a hunch. Using the FSM, I tested the unit and may have my problem. The valve does not move forward or backward. I can hear the solenoid trying to engage, but no movement. Can these be rebuilt or do I start digging for a used one?

 

[gummycarbs]

The valve does not move forward or backward. I can hear the solenoid trying to engage

I believe it's a stepper motor and barely moves with each input.

 

[Alan Jones]

According to the FSM the valve should move in or out depending on the order that you apply ground to the terminals.

 

[ppc]

You have to keep in mind the IAC has to control idle speed over a 1500 to 2000 RPM range in increments of 25 RPM or less. Each sequence of applying the ground to the four terminals is going to move the plunger very small distances as it is a stepper motor. If you can feel movement in the IAC when you ground each of the four terminals the device is probably working properly. You more than likely will not see the movement.

 

[Tedward]

I did something like staple gun a number of pieces of wire to wood.
Maybe 6 short separate leads next to each other like piano keys. Then twisted together at the other end. So when I made the connection to test the IAC valve I could run it over the 6 leads quickly. Could defiantly watch the valve move in either direction this way.