jodysgarage

I am still having trouble with my 1990 F150 5.0L 302 running rough.
I am going to try and replace the oxygen sensor but I need some help!
Can someone tell me where to locate it and if there is any advice I sure appreciate it!

Thanks

James_G

What kind of plugs do you have ?

willtransco

Should be on right side behind the CAT Converter on exhaust pipe....crawl under truck behind front tire passenger tire look up and you will see it.

ymeski56

He means just ahead of the Cat.

flareside_thunder

Yup, just ahead of the cat...and x2 on typ on plugs. If they're plats toss em out.

jodysgarage

Thanks for the replies.
They are not platinum plugs, but I will certainly keep that in mind in the future.

Thanks for the location. I just got this truck and don't know my way around that good.
But I have learned a lot in the past few weeks- especially from this forum.

I will check it out tomorrow and let you know if that takes care of it.

James_G

Your going to want NGK. I'm guessing since your o2 sensor is no longer working your truck is more than likely running rather rich.

They run hotter and can handle a richer mix.

I say this because my 94' 302 has no o2 sensor at all and it was running rough aswell and it turned out that my plugs had fouled out and came loose. (Plugs were only a week old) And they were Autolite Platinums (Sorry ford, they just suck).

So do yourself a favor and pay a little extra it'll be worth it.

Now does your truck run rough when in neutral and park ? Or only when under load ?

ymeski56

The last thing you want is hotter plugs if you have a well functioning O2 sensor. As O2 sensors age, they become less accurate & switching speed slows. For best MPG's, personally, I replace every 35K, & if MPG is any concern, replace by 60K.

"James" is running w/o ECU assisted fuel trim, not using the o2 sensor. He doesn't have a choice but to run a hotter plug to make up for the constant over-rich condition. Such is not your fate!

Stock Motorcraft plugs! 87 octane! No Double Plats!

jodysgarage

First, that was so easy I feel stupid for posting and asking where it was without looking first. Thanks for the patience.

Wow! Talk about a difference!

To answer the question James G asked, it was weak and idling rough. Even just idling it was weak and wanted to cut off. "Sluggish" is the word for the way it idled and drove.

But what a difference a $40 Oxygen sensor makes. It feels like it is finally breathing easy. Its idling stronger and doesn't sound like its ready to cut out any second.
I gained horsepower (and probably MPG too) without a doubt. It wants to accelerate now!

To ymeski56 : I got lucky on the plugs... I went to Advance Auto and told the guy the truck needed some TLC and I thought I wanted platinum plugs. He advised me to use stock Motorcraft plugs, which I did.

The O2 Sensor was the biggest bang for my buck in bringing this truck back to daily use.

If interested, I will tell you what I have done to this point.

First it is a 1990 F150 XLT Lariat 4x4 302 5.0L. I bought it one owner for $2000. 132,000 miles.
It had been used regularly for the first 10 years then used every week or two to haul trash and deer hunt. So I don't think it had much love in the last years. Power windows need work, AC is dead, and a few dents, but no rust and 4x4 works.
Came with new tires, battery, brakes, and alternator. Just got it two months ago.

I did all I knew to do as far as maintenance goes:
Flushed and changed Antifreeze (Replaced lower radiator hose)
Changed Oil and filter
New plugs and wires
New Air Filter
Changed power steering fluid
Changed front / rear diff and transfer case fluids
Changed PCV valve
Repaired PCV Vent Tube that runs to air filter
Finally, I changed the oxygen sensor

Each of these changes made it feel a little better, but the O2 sensor was the breakthrough. I feels so much better today.

I know there is still some "pep" to be found.
I only changed plugs and wires. I think I need to change the distributor cap as well.
is there anything else that comes to mind that I can do to get a little more life out of this?

Also, when i changed the oil, I used High Mileage Synthetic Blend (Castrol was on sale). I hope that was not a mistake, because I understand that you can't go back to traditional oil after changing to this stuff. Did I screw up?

The feedback so far has really been helpful...
Any more suggestions?
Thanks in advance.

ymeski56

I don't know why you'd want to go back to regular oil?

Do the "Seafoam" treatment to help rid yourself of the combustion chamber surface deposit build up, your tired o2 sensor caused. The is fun to do, & will immediately improve throttle response & idle. But don't add to oil, as you already changed your oil. 1/3 in the power brake booster Vac hose, while at warm idle. Shut off engine & and let sit for 20 minutes. Then restart & blow out the crap. The other 2/3 can goes in the gas tank. This will improve fuel atomization by the injectors. Safe for your new o2 senor & your Cat converter too. https://www.f150forum.com/f33/how-se...-1991-a-31505/

Here''s a Vid that another Forum member shot when he did his truck this weekend. So you'll know how much smoke to expect when the crap starts to burn out of the chamber surfaces. https://www.f150forum.com/f2/seafoamed-today-58880/

And spend a couple extra bucks & buy "brass" cap & rotor. It's actually cheaper, as they will outlast the stock versions two to one. You will also need them if you decide to do the Ignition system upgrade that is very popular around here w/ the Forum members.