Welcome Visitor! Please take a few seconds and Jawboy
New Member
- Joined
- Apr 13, 2014
- Messages
- 4
- Reaction score
- 0
- Points
- 0
- Location
- Oregon
- Vehicle Year
- 1994
- Make / Model
- Ford
- Engine Size
- 4.0 OHV
- Transmission
- Manual
Hey guys,
My truck has been flawless for years always taken the most care of her then all the sudden one morning...
When I start my vehicle the idle will jump between 1500 rpm and 2000rpm the check engine light will also turn on and off in synchronization with the idle. So check engine light on Idle goes up to 2000 check engine light off idle drops to 1500. Once the vehicle is warmed up the idle will continue to jump up and down and CEL on and off but at a lower rpm.
So I started ohms testing a few sensors and such (TPS, IAT, MAF, AICV) all tested fine then moved onto the wiring harness. Everything checked out fine except the circuit to the intake air temperature sensor. The voltage is supposed to read 5 volts from the harness.
The voltage will read 5 volts then as the check engine light comes on and the idle jumps up it will read 1 volt. Check engine light off, idle drops to normal, voltage back to the specified 5 volts. and the motor will continue to idle up and down and up and down.
I have tried my obd 1 code reader and the code reader says. "Vehicle not responding" when trying to pull codes.
Another thing is the truck will only cold start. Once warmed up it will crank and crank and crank but never start.
according to my chiltons book I may have a bad ecm.
Any help would be greatly appreciated. Thanks!
My truck has been flawless for years always taken the most care of her then all the sudden one morning...
When I start my vehicle the idle will jump between 1500 rpm and 2000rpm the check engine light will also turn on and off in synchronization with the idle. So check engine light on Idle goes up to 2000 check engine light off idle drops to 1500. Once the vehicle is warmed up the idle will continue to jump up and down and CEL on and off but at a lower rpm.
So I started ohms testing a few sensors and such (TPS, IAT, MAF, AICV) all tested fine then moved onto the wiring harness. Everything checked out fine except the circuit to the intake air temperature sensor. The voltage is supposed to read 5 volts from the harness.
The voltage will read 5 volts then as the check engine light comes on and the idle jumps up it will read 1 volt. Check engine light off, idle drops to normal, voltage back to the specified 5 volts. and the motor will continue to idle up and down and up and down.
I have tried my obd 1 code reader and the code reader says. "Vehicle not responding" when trying to pull codes.
Another thing is the truck will only cold start. Once warmed up it will crank and crank and crank but never start.
according to my chiltons book I may have a bad ecm.
Any help would be greatly appreciated. Thanks!
