Can a heated O2 sensor kill the engine?
#1
Can a heated O2 sensor kill the engine?
Hello everyone,
I was just wondering if the heated O2 sensor in the tail pipe, before the catalytic converter, can cause the motor to not start or kill it while I was driving.
Can it cause a no spark condition?
I have been working on a no spark problem and I was curious if the O2 sensor would cause this. I've pretty much tracked down to the TFI module and will be pulling the distributor tomorrow to test that.
I was just wondering if the heated O2 sensor in the tail pipe, before the catalytic converter, can cause the motor to not start or kill it while I was driving.
Can it cause a no spark condition?
I have been working on a no spark problem and I was curious if the O2 sensor would cause this. I've pretty much tracked down to the TFI module and will be pulling the distributor tomorrow to test that.
#4
Join Date: Nov 2006
Location: Memphis, TN 38135, USA, Earth
Posts: 5,495
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Don't pull the distributor. Mark its base with a scratch onto the intake manifold so you can set it back where it was, then just loosen the clamp bolt & spin the dist. for access to the TFI bolts. There's a special tool to remove those bolts, but it's only a few bucks for a cheapo at most parts stores.
If you suspect the HEGO, get a Haynes manual or a Ford service disk & a digital multimeter, and test it.
If you suspect the HEGO, get a Haynes manual or a Ford service disk & a digital multimeter, and test it.
#5
Thanks for the replies everyone!
The truck is a F150 1989 4.9 6 cyl.
Anyway, I have a Hayes manual for the truck but I did not see any mention of a HEGO. I will have to look again. I did find a webpage at another site that said the TFI module on this model truck is known for going out while running down the road. Because of its closeness to the engine, the heat from the block kills it.
There is an Ohm test in the manual but I don't see anyway to get it done without pulling the distributor. I do plan on marking the distributor location as well as the rotor's with a scribe. I dropped in a new coil since they are cheap, just to eliminate any problems with that. Coil is charged but, is not releasing. This is really what is making me think it is the TFI module. I'll know for sure if it is when I do the Ohm test.
I was kinda curious about the heated O2 sensor killing the engine though. I don't know to much about them. I'm an old school mechanic, before this injection stuff came about. I would kill for a Holly four-barrel setup right about now!
What happens if the O2 sensor goes bad and stops outputting voltage? Dose the system default to running rich or dose the engine shut down or something else?
I've been putting off learning all of the latest auto technology and I'm real happy at this point that my old work truck was built in the early stages of the new tech stuff. Maybe I'll be able to catch up, some day.
I just came across this web site the other day. Really nice to have a place where people can help other folks out!
Thanks again for the help! I'll try to return the generosity some day!
The truck is a F150 1989 4.9 6 cyl.
Anyway, I have a Hayes manual for the truck but I did not see any mention of a HEGO. I will have to look again. I did find a webpage at another site that said the TFI module on this model truck is known for going out while running down the road. Because of its closeness to the engine, the heat from the block kills it.
There is an Ohm test in the manual but I don't see anyway to get it done without pulling the distributor. I do plan on marking the distributor location as well as the rotor's with a scribe. I dropped in a new coil since they are cheap, just to eliminate any problems with that. Coil is charged but, is not releasing. This is really what is making me think it is the TFI module. I'll know for sure if it is when I do the Ohm test.
I was kinda curious about the heated O2 sensor killing the engine though. I don't know to much about them. I'm an old school mechanic, before this injection stuff came about. I would kill for a Holly four-barrel setup right about now!
What happens if the O2 sensor goes bad and stops outputting voltage? Dose the system default to running rich or dose the engine shut down or something else?
I've been putting off learning all of the latest auto technology and I'm real happy at this point that my old work truck was built in the early stages of the new tech stuff. Maybe I'll be able to catch up, some day.
I just came across this web site the other day. Really nice to have a place where people can help other folks out!
Thanks again for the help! I'll try to return the generosity some day!
#6
Join Date: Nov 2006
Location: Memphis, TN 38135, USA, Earth
Posts: 5,495
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Ford computers have always had a strategy for dealing with dead sensors or other wiring faults that corrupt the data used by the EEC/PCM. One of those strategies is HLOS: Hardware-Limited Operating Strategy. Another is FMEM: Failure Mode Effects Management. It means the engine will keep running as long as possible without doing damage that the EEC can sense & avoid.
But all of that logic is built inside the "box", so you really don't have to worry about it - just learn about the few sensors & actuators on the engine, and why they are where they are, and the EFI system will become REALLY easy to understand & work on.
You could unplug a HEGO and the engine would keep running, but if you short the power feed going to it (and possibly its heater on some years), you'll blow a fuse.
But all of that logic is built inside the "box", so you really don't have to worry about it - just learn about the few sensors & actuators on the engine, and why they are where they are, and the EFI system will become REALLY easy to understand & work on.
You could unplug a HEGO and the engine would keep running, but if you short the power feed going to it (and possibly its heater on some years), you'll blow a fuse.
#7
Thanks for the reply and the info, Steve.
I'm not going to worry to much about the O2 sensor right now. Besides, I'm going to have to take a torch to it or get the truck running to heat it up so I can get it out. It is heating up though, I left the key on for a few minutes to see if it was. So at least I know that part of it is working.
I havent got to the TFI module yet, got called into work, so I had to let it go. I'll have a chance to work on it some tomorrow.
Thanks again for all the help everyone!
I'm not going to worry to much about the O2 sensor right now. Besides, I'm going to have to take a torch to it or get the truck running to heat it up so I can get it out. It is heating up though, I left the key on for a few minutes to see if it was. So at least I know that part of it is working.
I havent got to the TFI module yet, got called into work, so I had to let it go. I'll have a chance to work on it some tomorrow.
Thanks again for all the help everyone!
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#8
Well, I thought I would update this thread for anyone down the road that might want to know the outcome to my situation.
It was the TFI module.
Since I am basically restoring this truck as things stop working, I went ahead and pulled the entire distributer Assembly and gave it a good looking over. It is important to mark the distributors location where it sits on the motor and make sure the rotor is in the same location when the distributer is reinstalled. I marked both locations and had no problems when I reinstalled mine.
There is one bolt (1/2 inch) that holds down a plate which keeps the distributer in place. I did have to run up the auto supply to get a deep well socket that would remove the bolts that hold the TFI to the side of the distributer. Under the TFI module is a medal pad that is its heat-sink. Mine was totally void of any heat sink grease. Being that it was dry, with no assistance in transferring away heat, this may have shortened its life.
The new TFI module did come with a clear heat sink grease, so if you have to buy one, make sure you have some whether it comes with the new one or not.
Anyways, once I had everything put back together, the truck fired right up and the heated O2 sensor is still in the truck. Although the truck is still running rich, its performance is much better.
Thanks to those who posted with help!
It was the TFI module.
Since I am basically restoring this truck as things stop working, I went ahead and pulled the entire distributer Assembly and gave it a good looking over. It is important to mark the distributors location where it sits on the motor and make sure the rotor is in the same location when the distributer is reinstalled. I marked both locations and had no problems when I reinstalled mine.
There is one bolt (1/2 inch) that holds down a plate which keeps the distributer in place. I did have to run up the auto supply to get a deep well socket that would remove the bolts that hold the TFI to the side of the distributer. Under the TFI module is a medal pad that is its heat-sink. Mine was totally void of any heat sink grease. Being that it was dry, with no assistance in transferring away heat, this may have shortened its life.
The new TFI module did come with a clear heat sink grease, so if you have to buy one, make sure you have some whether it comes with the new one or not.
Anyways, once I had everything put back together, the truck fired right up and the heated O2 sensor is still in the truck. Although the truck is still running rich, its performance is much better.
Thanks to those who posted with help!