I would also check the VSS.
My 89 dodge's is inline on the speedo cable and hangs below the brake booster.
It used to have issues with water intrusion on the connector.
Later on, the magnetic reed switch inside, would get stuck, and I would have no overdrive. So I'd stop, open hood, give it a few flicks with my finger, and then OD would be operable again. Waving a strong magnet near it would unstick the reed switch too.
When i got sick of the halfassed approach I putrchased a new VSS and all is well.
I do not use my cruise control much and do not know it it was inoperable during these reed switch episodes.
There is a 4 wire connector to my cruise control servo that was seriously degraded. I replaced that some years ago using a molex connector from a computer fan. I sealed the ends with clear RTV before splicing it in to make it more weatherproof.
Aways suspect the electrical connections first, and do not assume the presence of dielectric grease means the contacts within are oxidation free and making good contact. I recommend flushing old Dielectric grease with a cheap electronics cleaner and some mechanical abrading, then Using DeOxit d5 on the conductive mating surfaces. Mini swabs and bottle brushes and a strong light can reveal very oxidized contacts. When I saw how effective the Deoxit was i went a bit Nutty on every single connector I could find open and clean.
My 02 sensor and TPS sensor were especially dirty, and after I did all my engine sensor contacts it felt like I removed 500Lbs of weight from thre van.
https://www.amazon.com/Hosa-D5S-6-D...UTF8&qid=1485455636&sr=8-1&keywords=Deoxit+d5
https://www.amazon.com/Tamiya-Craft...&sr=8-4-fkmr0&keywords=tamiya+precision+swabs
https://www.amazon.com/DenTek-Profe...485455690&sr=8-2&keywords=dentek+brushes&th=1
The amount of oxidation that comes off otherwise perfect looking socket pin conductive surfaces blew my mind.
The pic above is one of my engine computer connectors after cleaning it with CRC qed cleaner. I foolishly declared it pristine. Later on, when I used the precision swabs with Deoxit D5, well about 6 swabs turned black and got shredded as if I was using a black sharpie on them, then scraping them on 220 grit sandpaper. By the end the of my cleaning the swabs were staying pinkish from the d5, and the contacts gleamed like polished chrome.
The Deoxit products are amazing in my opinion. Use it regularly on one's Phone usb connections and they reseat with that click one forgot used to exist, and the battery seems to recharge faster too.
