JayBanion

Ok, so my car is a 1988 GT, headers, o/r midpipe, flowmasters blah blah blah. Anyway, when i start the car when its cold or like first thing in the morning it will start up and idle good. When its warm and i start it, it will fire up the drop to about 500rpms then jump back up to around 1000 then back down to 500 it will do this about 3 or 4 times then it will idle good again. When idling then it will move around between 800 and 1000rpms. Also once in a while while driving the rpms will hang a little between shifts. What the problem, I just bought the car and am not familer with the 5.0 that much coming from a 4.6 SOHC. I was thinking IAC, so Im gonna clean that tommrow morning and see if that helps. Any other ideas?

dimebag

clean the iac... but SD cars are good for doin that, just something to get used to... is it cammed? or any of that fun ****?

stangbanger87

my 87 sd does it to sometimes . and dime you haven't sold it yet! looks good for a 427 stroker car

rebel_yell

my car does the same thing and when its cold it can be really cold blooded so i cleaned the iac and no better so i bought a new one and its a little better.....but not fixed so i guess its just one fo those SD car woes lol

88foxGT

When I first got my 88, it surged like that too. I did just about everything. Cleaned the IAC, pulled the throttle bottle and EGR spacer apart, cleaned them.Replaced the EGR, throttle body and IAC gaskets. Installed new plugs, wires, cap, coil and rotor. Also replaced the fuel filter. The surge is nearly gone now. I also cleaned lubbed and adjusted the throttle cable/bracket/spring. Another suggestion you could try is to get an adjustable fuel pressure regulator.

jayh88gt

clean iac, clean tb, raise idle 1/4-1/2 turn

onefast86lx

test your throttle positioning sensor, use an ohm meter on the green and black wires and if its adjusted right it should read between .96 and 1.0 volts. to adjust it loosen the screwn and turn it until it reads correctly. once u tighten it back up hit the throttle and make sure that the reading goes up to almost 4.98 volts and comes right back down to .98. if the reading stays up u need a new sensor