Curious Idle bump MPH dependent (New IAC)

[EvanH]

Hi all. I put this in the facebook group, but wanted to have it here too.

I replaced my IAC. So now I have good idle, good hot starts without holding the pedal slightly, idle kicks up for AC and PS to include when the fans come on.

BUT, something that has never happened in 18 years of owning the car. If I coast up through about 15mph, in neutral, my idle jumps up from 700 ish to 1400 ish. If I coast down through 15mph ish, my idle will drop back down. I can be at highway speed (60) push the clutch, let off gas pedal, engine rpm drops to 1400 and holds. All until I slow till 15ish. Engine cold or hot. So if I slow with my gears, and the mph is higher than 15, and rpm is around 1400 the car will wanna pull itself.

Engine vacuum above 18(book says approx 19)166k miles
Idle with the brown plug and pin 10 of the diag port grounded ~700
Before new IAC, base timing was about 6
I replaced my old IAC and swapped a TPS that was known good. (Vacuum and idle did not change)
Cold idle 1400 and falls consistently until shortly before low fan kicks on.

VAC gauge.jpg

[stealthee]

I'm wondering if with the bad IAC you lost one portion of your idle driver on the ECU?

Also your 2nd video is marked private.

And lastly, you still in Uniontown, PA area? I'm literally 10 miles away.

[EvanH]

Should have the second video fixed now?

I have a second ECU to try, but they had both been in the car over the years up till now...Think I should still try swapping?

I am close to the area. Moved a little north closer to west mifflin. Been busy with the job over the past 7 years, its been things like drive it and don't look at any of the issues, lol. Finally had some time off to do a lot of shit I have been meaning to take care of.

[stealthee]

Trying to swap the ecu couldn't hurt as a trial and error thing.

And I'll actually be up by West Mifflin tomorrow. Going to Dave & Busters.

[EvanH]

Trying to swap the ecu couldn't hurt as a trial and error thing.

And I'll actually be up by West Mifflin tomorrow. Going to Dave & Busters.

What time? I don't know my full schedule tomorrow, but I will be in Ohiopyle for a little before and during lunch.

[stealthee]

We're going around 1.

[EvanH]

Unfortunate change of plans for me, car is fine, lol, but I am now in a time crunch to get out for work. So things will have to wait till I get back. Luckily it's not causing any drivability issues. And oddly enough a massive amount of my backfire on deceleration has disappeared. I sounded like those asshats who rev to get backfires, but just coasting down a hill. So I am happy about that. Like one or two "(sound)pups" from the pipes down the entire Summit.