Everyones Hero

I have an '86 GT w/ a 5.0 HO motor. It says HO on the plenum. I have a few known upgrades & a couple of possible upgrades.

It definitely has:
-MAF conversion
-Headers
-Exhaust

Possibly has:
-Cam (if I pulled the cam would I have to use a mic to see if it's aftermarket?)
-3.73 Rears
-Aftermarket pistons/rods (Would I be able to test this by comparing the compression vs a known stock baseline?)

The problems:

It has an idle problem. It'll rev from 500-600rpm to 2000rpm over & over. It happens when it's hot or cold. Sometimes it won't do it & sometimes it'll just die. Is that a sign the MAF conversion could have been done wrong?

The speedometer doesn't work either. I was told by the seller that it's a clip that goes on the transmission but I don't know where it is.

The rear-hatch won't latch. I can just pull up on the hatch & it'll come open.

The motor in the car is a fuel-injected 5.0L HO motor. Did the '86 GT come with a fuel-injected HO motor? If not what year would have this motor?
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I looked through the MAF conversion thread. Tomorrow I'm going to check the ECU & wiring to see if that was done correctly.

Thanks for any advice/input.

-Nick

mjr46

cam..on the heel will be stamped a part number if it's aftermarket
idle...run a koer and look for codes
clip on tranny.., pull the drive unit and that cable goes into down on tranny and make sure gear has clip on it

hatch...check striker plate adjustment
h.0 =yes in 86