RPM surge when turning on the blinker/ Cruise control turning off

I have searched for months, and I give up.

Bought the truck last November and have had this issue from day one. Owner I bought it from said he never noticed this issue when he had it.

This only happens when I'm on the interstate, in final gear.

Cruising on the interstate, when I turn on the blinker, left or right, the RPMs surge up and down about 300 or 400 RPMs. Pretty fast up and down.
In addition, when I have cruise control on, cruise control will turn off and the RPMs will do their little surge.


Only thing I can think of that could be causing the issue, is the multifunction switch on the column.
The blinkers and tail lights are the original style bulbs. Headlights are HID and I have an LED reverse light wired to the reverse lights.

Thoughts?

99 Tacoma, 3.4, 4x4, Automatic.

 

Check the grounds "IG" "EA" Theyre the triangles on the diagrams of the pdf i attached

 

10-4,
I'll be checking them some time this morning when I get off work and get back.
Really hope this works, so fed up with it.

 

Factory or dealer installed tow harness? When these go bad they can do all sorts of fun stuff. Your symptoms included.
I had an issue last year where if driving w/ cruise control on, signal a lane change (left or right) blinker would disable cruise. Also, if parked with hazards on, the relay would cause the gear shift lock button (auto) to visibly and audibly move and click in time with relay switching.
I finally traced it to the harness - removed it - trouble free.
Keep us posted.

 

Ok, I will try that as well. I believe it is the factory wired harness.

I checked the IG and EA grounds, and everything seems to be good, so this will hopefully be the ticket.

I’ll give updates for sure, and maybe do a little write up on some of the things I find.

Thanks for yalls help.

 

Finally fixed my problem!

Got a few minutes yesterday to track down my trailer wiring harness. I found the little black box tucked way away up into the body of the bed. I had to pull both the taillights out and disconnect the splitters for the wiring harness and plug the main connectors back into the lights.

Bad news, I no longer have trailer wiring until I replace the harness.

Good news, I no longer have my surge problem and cruise control works like it should.

Bonus, my rpms run lower on the interstate, getting better gas milage, the tail lights seem to be way brighter.

Thanks for everyone’s help, I have tons of other little issues to solve on my truck, so I’ll probably be posting again.