I have a 1989 Bronco with 302. Problem is with idle at startup. It is hard to start, but when it starts, it jumps to 2000rpm for about 10 seconds, then drops to under 500rpm and dies. It will do this several times until the engine warms up. After it warms up, the idle is fine, however, it's still is hard to start. I have pulled codes, shows nothing. I have replaced the IAC, TPS, MAP, ECT put new plugs and wires along with cap and rotor, timing checks out ok and I've also replaced the fuel filter and cleaned throttle body. After all this, I still get exactly the same thing, no difference. I now suspect a vacuum leak or EGR valve. I'm tired of spending $$$, I need help please!!!!