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I'm hoping someone here can help me out. I've just inherited an '81 F250 Custom (I assume it's custom because it has a motorhome instead of a bed). The engine only has 66k miles on it, and given everything I've read that means it's barely warmed up yet. So I'm trying to tune it up, and I can't figure out where the o2 sensor is. I'm not even sure it has one. I tried looking where suggested in this thread: https://www.ford-trucks.com/forums/9...en-sensor.html but had no luck. Any advice would be very appreciated!
We need to know a lot more than the year. Like the engine, transmission, and whether it has an ECU. But, I doubt it does, and if not it won't have an O2 sensor. I have two 81 F150's and neither came with an O2 sensor as they didn't have ECU's. The 82 F150's frequently did, but not in the heavier trucks as there was a GVWR cutoff at 8600 lbs, if I remember correctly.
So, tell us more about your motorhome. And take some pictures and post them. Oh yes, and welcome to FTE!
Hard to tell, but there are some things which lead me to think the engine might be computer controlled. I do not see a vacuum canister on the distributor. Most 49 state 4.9L F150s did not gain the computer control until 1984. Is yours perhaps a California equipped model?
Anyway, the O2 sensor [if there] will be located in the exhaust manifold right above the outlet. It is mounted on the top side.
Oh yeah, welcome to the forum!
Last edited by 1986F150six; Aug 20, 2014 at 01:28 PM.
Reason: Welcome
I think David is right - it is computer controlled. The E1TF-12A651-C1A is a "Control Assembly Engine air/fuel ratio", as called out in the master parts catalog. However, I can't find the exact match and the closest I can get is an E1TZ unit, which is for an 81 F100/150 2wd with a manual tranny in ...... CA.
And, he's right about where the O2 sensor should be.
I was looking in my 1982 Ford Emissions and Diagnostic manual (my book is for '82 but I believe it is same for 1981 year), and it shows the only 4.9L truck with an MCU is for "California (under 8500GVW)" and the F-100 (which yours is not).
Your truck came equipped with the "Themactor Air" system (you photos show the air pump is gone). You should also have a feedback carb (assuming it wasn't replaced). The diagrams also show an O2 sensor - so I don't know what you have. I can see the (red) "Self-test" connector near the MCU in the photo.
Do you still have a catalytic convertor?
I think you are going to run into tuning problems with the MCU since not all of the systems/feedback necessary are installed. You are probably running in limp mode with fixed timing right now. If it were my truck, I would ditch the MCU and swap to a standard distributor/ignition system.
PS. What is the single wire going to with the connector that is hanging in the last picture you posted?
I was looking in my 1982 Ford Emissions and Diagnostic manual (my book is for '82 but I believe it is same for 1981 year), and it shows the only 4.9L truck with an MCU is for "California (under 8500GVW)" and the F-100 (which yours is not).
Your truck came equipped with the "Themactor Air" system (you photos show the air pump is gone). You should also have a feedback carb (assuming it wasn't replaced). The diagrams also show an O2 sensor - so I don't know what you have. I can see the (red) "Self-test" connector near the MCU in the photo.
Do you still have a catalytic convertor?
I think you are going to run into tuning problems with the MCU since not all of the systems/feedback necessary are installed. You are probably running in limp mode with fixed timing right now. If it were my truck, I would ditch the MCU and swap to a standard distributor/ignition system.
PS. What is the single wire going to with the connector that is hanging in the last picture you posted?
Amen! You aren't going to get it running correctly with any of the system gone, and much of it is. Those systems are all-or-nothing systems, so you either have to replace the missing pieces or do as CB suggested and go to a DS-II system and no feedback on the carb.
CountryBumkin, PatrickOmally is correct about the wire.
It seems a simple test might be if you can tell me where in your diagram the o2 sensor is shown. If I have one there, then perhaps I do have the Cali model?
I've gone under the truck and I believe what I saw was the catalytic converter, as someone at the parts store told me to look just before it for the o2 sensor (didn't see it there).
This transformation into a DS-II system, how difficult is that. On a scale of 1-10, my car knowledge is probably a 2. I'm a computer guy in a strange land.
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