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87 F150 Stalling On The Road

1987 Ford F150 XLT Lariat. 302, 5.0 automatic. 120k miles.

Hi, this is my first post and I wish I discovered this place last year when I got this truck. I changed a lot of the parts (Carfax said it sat for 10 years). I’ve never worked on a vehicle but wanted to learn and wanted an older truck.

Recently, it’s been stalling intermittently on the road. About 40 mph, flat ground. Probably a dozen instances. It’s unpredictable and there isn’t a pattern to it happening. New map sensor, tps, EGR, IAC valve, plugs and wires, pcv valve, o2 sensor, ignition coil, fuel pumps, fuel and air filters, tfi module (mechanic replaced the tfi, I did the others over the past year). A lot of the stalling symptoms seem to point towards the ignition switch, but I can’t seem to rule out the PCM, distributor, or pip sensor because symptoms match those to varying degrees.

When it stalls, I put it in park after coasting off the road and stop, turn the key, and it fires up without issue. My battery is a 24 (the previous owner had this in the truck, so I assumed it was correct and bought a new one of that size), but the true battery size is 65, I’ve since learned. Would that matter? Any insight and help would be greatly appreciated. My diagnostic knowledge is minimal, but I can replace parts and I can learn. Right now I’m afraid to drive it

You’ve got to determine first if the stalling is caused by lack of spark, or lack of fuel. When it stalls out, does it then crank and not start for a while too? If so, that’s a good time to check for spark. Google “how to check for spark” and be prepared with the stuff you need for the test in the trunk for when it happens.

If it always starts up right away after the stall out, you could have an auto electric shop install a volt meter on the battery power to the ignition circuit installed in the passenger compartment that you could monitor as you were driving, and take note if the voltage drops when it stalls. The same technique can be used to monitor other voltages, like the fuel pump power voltage.

Have you tried driving with just a single key in the ignition switch, rather than a key ring full of keys? Sometimes that can provide a clue.

OP states in his post it starts right up.

I don’t see a magnetic pick-up coil on the list.,1987,f-150,5.0l+302cid+v8,1121724,ignition,distributor+pickup+coil,7176


That’s the same as a pip sensor if I’m not mistaken. It’s one of the things that I seem to have narrowed it down to

That volt meter is very intriguing. I’ll have to look into that. Is it something that I could buy and do myself, or is it something very expensive and complicated? I didn’t know such a thing was possible. And the truck does start right back up after stalling. I haven’t tried just the single key, but I don’t have a big keyring and lots of keys anyhow (ignition, door, tool box, and house key) but I’ll have to give the single key a try. What potential problem would that likely indicate?

There are inexpensive gadgets you can plug into the cigarette lighter to monitor the battery voltage. That might be a place to start if you do it yourself. Monitoring other voltages would require a pair of wires be connected at the monitoring point, and run into the passenger compartment, where you’d have a hand held volt meter on the other seat, taped to the dashboard, etc. Harbor Freight often offers coupons for free hand held volt meters (search their website on DVM) w/any purchase, or they can be purchased for less than $20. Running wires around the truck that aren’t designed to be there requires some common sense. They have to be placed so they don’t get pinched, or in the way of something that’s moving (like a fan), etc. Otherwise you could get a short circuit and a car fire. So if you want to do that, suggest to have somebody w/experience show you how in person.

If it never stalled when you used a single key, replacing the ignition switch would probably address the problem. The weight of the keys dangling and bouncing around as you drive can damage the ignition switch over time. And there’s a lot of time on your 87’s ignition switch.

If a new fuel pump is not too expensive or hard that is 1 thought, I would lean toward driving it with one key in the ignition as another, and just for kicks move the steering wheel out of the 2 lowest tilt positions.

I will have to get one of the cigarette lighter ones. I definitely would leave the other to a mechanic.

One thing I failed to mention. When it stalls, the lights and radio (if on) won’t die every time, same with power steering. When coasting to safety, the headlights stayed on and I could steer into the median/ off the road

I did install a new in-tank and rail located pumps. I don’t use the rear tank, as the previous owner said it doesn’t work. They were installed about 3 months ago

So you have dual tanks? I would be looking at the switch valve also. No reason both tanks should not work, fuel filter again might not be a bad idea.

The lights and radio should stay on unless the stalling is due to an electrical problem. The power steering should lose power assist but the steering will still work, with some effort, which may not be noticeable at highway speeds.

See for plug in voltmeter. Search for “auto cigarette voltmeter”

Thank you all for the replies and the help, I really appreciate it. I’m definitely getting a voltmeter.

Now, to figure out how to swap the ignition switch…