Need Ford 302 Efi expertise -update

[Art Vandelay]

Shot in the dark but this is probably the best truck forum on the internet and the ford forums about this are a little judgmental.
Just grabbed an 86 F150 with a 302efi.
seems to run rich, idles high and exhaust is brutal. Looks like the cat might have been gutted.
Any thoughts, advice about idle and will removing the dead cat mess up all the efi sensors?
I know that might be vague, but I’m hoping a couple of you guys know these engines inside and out and we can continue this conversation.

 

[legopnuematic]

I not a fuel injection or OBD 1 expert, but there only should be an upstream O2 sensor, meaning it doesn’t know or care what is downstream of the sensor. Newer stuff with an up and downstream sensors uses the downstream one to Monitor catalyst efficiency more or less.

 

[Ricko1966]

Shot in the dark but this is probably the best truck forum on the internet and the ford forums about this are a little judgmental.
Just grabbed an 86 F150 with a 302efi.
seems to run rich, idles high and exhaust is brutal. Looks like the cat might have been gutted.
Any thoughts, advice about idle and will removing the dead cat mess up all the efi sensors?
I know that might be vague, but I’m hoping a couple of you guys know these engines inside and out and we can continue this conversation.

First thing to check is the coolant temperature and intake air temperature sensors. ( that is general efi trouble shooting,not all cars have both). Anyways if the ECM thinks it is negative 40 outside it's going to feed a rich mixture. Make sure all vacuum hoses are connected and not split,a vacuum leak, and the MAP sensor thinks you have the throttle open so fuel gets added. Also make sure the ignition plugs,wires,cap and rotor are good. Also see if it has any codes.

 

[DoubleDingo]

I know nothing about those. I will share an experience I recently had with my 1991 Cherokee. It ran fine, but then it started smelling to high heaven of exhaust fumes. I mean you got gassed out idling at a red light. Had to roll down the windows and hope for a breeze. The o2 sensor went bad and it made it run rich. I got a new one, along with a new cat and muffler. No more smells. I wouldn't get rid of the cat. Fix the rich condition, and add a new cat, and you should be fine. I can tell when new cars have a bad cat now, and you'd be surprised how many there are out there on the road.

 

[Art Vandelay]

Throwing Codes:
P0113-intake air temperature censor circuit high input
P0118- engine coolant temperature circuit high input
P0102-Mass/volume air flow low output

 

[fast 99]

Unless the cat is plugged a bad cat will have no effect on driveability with OBD1 vehicles. Check all the grounds and when connectors are unplugged inspect for pin push back and corrosion.

 

[Ricko1966]

Throwing Codes:
P0113-intake air temperature censor circuit high input
P0118- engine coolant temperature circuit high input
P0102-Mass/volume air flow low output

Okay first check resistance hot and cold on IAT and CTS. Mass air flow check for leaks in the intake boot and plugged Cat.

 

[Ricko1966]

Throwing Codes:
P0113-intake air temperature censor circuit high input
P0118- engine coolant temperature circuit high input
P0102-Mass/volume air flow low output

Did you read my first post? It's almost like I'm psychic. Like madam Cleo. LOL

 

[Art Vandelay]

Did you read my first post? It's almost like I'm psychic. Like madam Cleo. LOL

Madame Cleo lol… I ordered a new ACT sensor last night and I’m hoping that’s what it is. The one in it was pretty dirty.

 

[77Dmax]

I would check if all those sensors share a common ground.

 

[YakkoWarner]

Is yours a throttle body style system or that odd looking 1st generation multiport?

I had a Lincoln with the 302 and Ford's version of the throttle body - it was great until the insulation started flaking off the wiring (whatever they used in those years for insulation started breaking down and I had multple bare copper strands visible everywhere) and that pretty much killed it. Which was a shame because I really liked that car.

I had a 1989 Ford truck with that later version 1st gen multiport as well. It ran well but ate exhaust manifolds like a kid eats cereal. They were replaced at least 3 times, always broke in half right in the middle. So a broken exhaust manifold would be one of the 1st things I'd check for on that era truck - that would play havoc with the O2 sensor and possibly cause it to go rich, and be loud as well.

Oddly enough mine ran very poorly until the check engine light came on, and then it ran beautifully. Only reason I gave up on it was because the manifolds broke again, and that started a chain reaction of having bolts break while changing the manifold, which meant having one of the heads pulled to get the hole drilled and helicoiled, and then something else went wrong after putting the head back on and the end result is I ended up buying a Suburban instead...

 

[Art Vandelay]

Engine

 

[Art Vandelay]

Replaced the IAT sensor and slight improvement, not surging like it did. Will move on to ECT and sensor at Cat.

 

[Ricko1966]

Replaced the IAT sensor and slight improvement. Will move on to ECT and sensor at Cat.

I wouldn't bother with the O2 sensor at this point. Especially if it's rich during the first 5 minutes of operation. While the engine is warming up the O2 sensor is not in use.

 

[edgephoto]

I worked on those when they were new. In those days drivability was a huge issue. Clean and set the throttle plate, Air temp sensor and coolant temp sensor failed regularly. MAP sensors rarely failed but the vacuum line to them would get dunked up with this jelly like substance. TPS would go bad all the time.

I wish I could remember more but off the top of my head that is all I have for now. These old systems had very little adjustment that the ECM could adjust for unlike modern cars so one thing out of whack caused big issues.

As Rick said don't focus on the O2 sensor. At idle most of the time they were in open loop. Focus more on items used to set the fuel map. Temp sensors, throttle position, MAP sensor. If you have vacuum leaks it will cause all kinds of issues. Make sure timing is set right too