high idle problem

[rwichryk]

I hope someone can help me with this because nothing I have done helps, and I've never seen a car do this before. When I first start the 1996 explorer, it idled up to about 2800rpm. After about 1-2 minutes it will drop to about 1000 rpm. If I barely tap the gas, it idled up to about 2500 rpm. It finally cones back down after about 10 seconds. If I put it into reverse or drive, isles up to about 1800rpm, then eventually, if I hold the brake on, it drops back down. If I don't hold the brake on, it will go until it is out of gas. Then if I put it back into park, it idled up to about 2800rpm again for a second, then back down. So far this is a list of all the things I have replaced trying to fix the issue: tos, iac, egr, egr vacuum control, all three O2 sensors, maf, I adjusted the idle screw, cleaned intake manifold, cleaned butterfly control, and lubed it. I asked independent garages, as well as Ford mechanics with no ideas. I have also performed a smoke test on it for possible vacuum leaks. Found none. Only places I found smoke coming out was the air cleaner, the egr valve, and the small port on the iac. If anyone knows what is causing this, please help me out, as I am at my end on this.

 

[FR-425]

So if you take your foot off the brake this thing goes runaway?

I guess my question is: is it really reving 2800 or is it just the tach?

2800rpm neutral drops pretty exciting. burn rubber exciting.