I thought I would do a write up after finally finding the problem (and solution) to my 12 month saga of chewing through IFS (Ignition Failure Sensor) units.
For those who don't know, the IFS unit is a little black sensor box that sits on top of the front cam cover. You must remove the engine cover to get to it. The sensor gives the signal to the rev tacho. When it dies, your engine will die and not start. It's a similar symptom when your CAS (Crank Angle Sensor) dies. Sometimes the problem is misdiagnosed between the 2 sensors.
Fortunately the IFS is a lot easier to get to and can be bypassed to get you home or to a mechanic. Using a paper clip, you can bridge pins 3 and 4. You will lose the rev signal though.
So onto my story. Mine died for the first time 12 months ago. Got a replacement from Steve at TME and all good. When originally trying to figure out the problem as to why the car wouldn’t start (as it could be many things), it looked like the IFS dying was starting to become common with other VR4 owners.
It then died again 6 months later, annoyingly 400kms from home. This was an expensive lesson to learn as it was a $600 tow to get the car home. I looked around the engine for anything obvious that would cause a new IFS unit to die so soon. Everything looked ok. The sensor plug itself was fine, the rest of the loom looked fine, and I even put brand new braided engine loom hoses from the coil packs and IFS to the main loom.
Deciding not to chance another unit, I also put a fuse in the wiring loom to the sensor (pin/wire 4). I used a 10amp fuse, which I soon found out was overkill.
Thinking I had all bases covered, the new IFS only lasted 2 weeks. And the 10amp fuse didn't catch it. So if you're reading this in the future, use a 7.5. This was becoming an expensive problem to get to the bottom of; and now I didn't trust driving my car anymore.
I got the car running (using the paper-clip hack), and started wriggling everything I could get my hands on connected to the main engine loom. Pop. The fuse went. Wriggled the IFS and plugs to the coil packs, all good. Wriggled the loom plug to the MAF/intake sensor, all good. Grabbed the massive snake like main loom under the intercooler hose, pop.
So to get to the point, the problem was the metal clamp right above the thermostat/top radiator hose. It had slowly rubbed against the main loom and was touching an earthing wire, short circuiting the next sensor in line, the IFS. The clamp looked old and nasty, and it would only be a matter of time until it happened again. So got rid of it and resealed the engine loom.
I'm glad to say that the car has been running perfectly since.
Below are images of where to find the problem.
For those who don't know, the IFS unit is a little black sensor box that sits on top of the front cam cover. You must remove the engine cover to get to it. The sensor gives the signal to the rev tacho. When it dies, your engine will die and not start. It's a similar symptom when your CAS (Crank Angle Sensor) dies. Sometimes the problem is misdiagnosed between the 2 sensors.
Fortunately the IFS is a lot easier to get to and can be bypassed to get you home or to a mechanic. Using a paper clip, you can bridge pins 3 and 4. You will lose the rev signal though.
So onto my story. Mine died for the first time 12 months ago. Got a replacement from Steve at TME and all good. When originally trying to figure out the problem as to why the car wouldn’t start (as it could be many things), it looked like the IFS dying was starting to become common with other VR4 owners.
It then died again 6 months later, annoyingly 400kms from home. This was an expensive lesson to learn as it was a $600 tow to get the car home. I looked around the engine for anything obvious that would cause a new IFS unit to die so soon. Everything looked ok. The sensor plug itself was fine, the rest of the loom looked fine, and I even put brand new braided engine loom hoses from the coil packs and IFS to the main loom.
Deciding not to chance another unit, I also put a fuse in the wiring loom to the sensor (pin/wire 4). I used a 10amp fuse, which I soon found out was overkill.
Thinking I had all bases covered, the new IFS only lasted 2 weeks. And the 10amp fuse didn't catch it. So if you're reading this in the future, use a 7.5. This was becoming an expensive problem to get to the bottom of; and now I didn't trust driving my car anymore.
I got the car running (using the paper-clip hack), and started wriggling everything I could get my hands on connected to the main engine loom. Pop. The fuse went. Wriggled the IFS and plugs to the coil packs, all good. Wriggled the loom plug to the MAF/intake sensor, all good. Grabbed the massive snake like main loom under the intercooler hose, pop.
So to get to the point, the problem was the metal clamp right above the thermostat/top radiator hose. It had slowly rubbed against the main loom and was touching an earthing wire, short circuiting the next sensor in line, the IFS. The clamp looked old and nasty, and it would only be a matter of time until it happened again. So got rid of it and resealed the engine loom.
I'm glad to say that the car has been running perfectly since.
Below are images of where to find the problem.
