Hello everyone. I'm brand new here and a recent owner of my 1988 F-150 XLT Lariat with the 4.9L inline 6. 4 speed manual w/overdrive. Electronic fuel injection. Was my grandfather's truck, ordered new from the factory. Really a family heirloom that I have no intention of getting rid of for anything. I've been giving it some TLC recently to the tune of $1700 at a wonderful local shop here in Fort Wayne, Indiana where I live. I limped it in to them after it had been driven down to me from Chicago after I'd had it for about a week. It was stalling out as a result of the distributor overheating. It would quit, and I would try to turn it back over and it would just turn but because of the overheated distributor it wouldn't produce spark until it had cooled down. That wasn't the only thing they did, so no worries on the price there, here's the list of things they repaired for me:

Remove and replace E brake cables to rear brakes(they were frozen)
Remove and replace push rod side cover and gasket (it was leaking oil)
Remove and replace clutch slave cylinder seal at snap ring (leaking)
Remove and replace steering gear (chowdered and shot)
Remove and replace rear trans seal (it was bad)
New Wire set
New Distributor
New Plugs

I get the call that it's done and go to pick it up. There's a new problem though and they couldn't sniff it out in budget. When it idles now, rpms will dip from 800 or so to 500 or lower at random for a brief second. Not long enough to stall the engine. But regularly. Thought that was the only problem, but the rpm issue persists when you're driving and is worse overall. At or around 2k the rpms will either stutter down to 1k in a split second and jump back up or peg the needle at zero and I've got no throttle at all, it just "dies". And it will just coast to a stop and die unless I clutch it in and then the rpms will come up to idle again and stay there then I can shift to the appropriate gear for my speed and continue. This issue at ~2k rpms is persistent across all gears.

I'm wondering what this new problem is because when you're driving it's absolutely jarring and you've got no pedal, no throttle. Please help if you can. If it's something that's happened to you please chime in. I need help and want to do what I can by myself if possible. It'll drive but this feels super dangerous. I love this truck and want to put another 200k on it.

Current mileage is 122519

Thank you so much for reading and commenting

David

 

I would first pull codes, have you done this?

Any pinging?
Did it do this before the new distributor? Did new distributor come with a new ignition module?

 

Hey David,
Am restoring one left for dead myself.
Sounds like you need to get yourself an OBD1 code reader and learn about the systems in your truck. They are first generation and your symptoms may be easily cured with a proper diagnosis. Knowledge is more powerful than any budget that throws $$'s at problems. Just my 2 cents. You will learn and hopefully diagnose the exact problems. Very good investment IMO. Careful with those unscrupulous shops! Lots of knowledge here for the harvesting!

 

Your will also have to take a close look at all your vacuum lines, looking for loose, cracked, removed and leaking lines.

 

I 2nd and 3rd what was said before. Unless you are dependently wealthy and have a place where you can do some work invest in some good tools and manuals. I found the original shop manuals for my truck on ebay. These trucks are very easy to work on and you will find a ton of information online. To give you an idea all the work done by the shop you could have done yourself for a 3rd or less of what they charged you.

Idle issues are very common on these trucks. From what I know (and I am not a mechanic) it could be anything from a faulty sensor, a vacuum leak to a bad PCM. You need to start testing and checking step by step to eliminate every issue the truck may have.

 

My baby.

Thank you guys. I will be exploring all of these options. I definitely want to keep her on the road a lot longer, she's pretty, and important to me. Will start with possible codes and go from there. Was thinking vacuum too or an O2 sensor

 

Keep in mind all sensors on these trucks can easily be tested with a test light and or multi meter. Codes can be read with a paperclip.

Beautiful truck!

 

Thank you! Looking into codes now and how to check them. My baby is far from the brink of death but yeah I'm super excited to get her moving again. I've posted a picture in my first reply above. Cheers!

 

No I have not pulled codes yet. Learning to do that now. No pinging, just dead throttle as described. Yes the ignition module was what was overheating according to my shop. They replaced the distributor and it has a new ignition module. They did plugs and wires at the same time.

 

Looking into all that, thank you very much! My grandfather offered to pay for the repairs so I couldn't deny his help lol I'm a truck driver, so it was more cost/time effective to have the shop work on it while I drove. The vacuum lines could likely all use to be replaced. Will look into that.

 

I'm seeing that! Looks like a simple jumper and basic knowledge of blinking light and I can get codes. Fascinating.

And thank you! She's gorgeous

 

The paper clip method is such an invitation to errors that, when you see how cheap a code reader is, you'll wonder why you didn't start there. I would also get a fuel pressure gauge, also, as that's another part of the answer.
And, yes, the Ford service manuals are the best to have.
Learn how to pull the computer to check it for internal damage.

 

The ignition module can be tested, but will only show faulty if you have a no-start. the PIP and ignition module can give you trouble related to heat.

Ask the shop what they used in the install(dielectric grease or thermal paste). If it was a loaded distributor they probably dont even know because it came pre-installed.. Most of the modules come with dielectric grease, which is incorrect and actually holds heat in the module rather than transferring it like the design intends.

I couldn't find any locally, no electronics stores near me.

My first guess based on your description is an issue related to this.

If they didnt use a thermal paste, remove it and clean both surfaces and put a thin coat of this on both surfaces and re-install. I'm not sure if damage has already been done at this point from heat. Also alot of the new ignition modules you buy are junk out of the box, I bought a motorcraft NOS unit and haven't had any issues since,
I went thru 4 that gave me various problems, one of which left me stranded like someone turned the key off. It wouldn't start even after cool down.(i put my spare on and drove home)

I advise you always keep the socket and tools to change it with you, along with a spare. Keep in mind alot of socket sets do not have the correct size(i cant remember off the top of my head)

 

According to the shop, all Ford motorcraft parts were used in the replacements. I'm thinking perhaps some sensors need replaced. MAP sensor, knock sensor, start there perhaps. Can do those easy. EGR stuff too.

 

I will definitely look into that and clean/replace