uvastang

i have a 94 mustang gt 5.0 and it idles fine in park around 1000rpm.... but when i put it into drive it drops to 500 then rises to 1000 every time.. almost down and back up every second or two.... as i get on the gas it seems to still do it as rpm increases but not as severe.... ive asked a few friends and they mentioned maybe the idle air control... egr valve... maybe a disconected vacuum hose.... any one have any ideas or ever had this problem please let me know!!!!!!! thanks in advanced!!

projectresto83

It is idling a little high so I would check those and see what happens.

wrenchturner75

good ol rolling idle problem! there is a ton of info here just on this subject alone. try using search youll find what your looking for. good luck! ps punch in idle surge for the search youll get a lot of info.

Joel5.0

DIY KOEO/KOER/Cylinder Balance Self-Test .......1k rpms idle setting is too high from the 700'ish idle target in the ECM. Once Drive is engaged, the system will try to reach that idle target value programmed via the ISC or spark advance control.

white93pony

like was said either a vaccum leak or iac valve. go buy some b-12 and spray around the engine and see if the idle changes then pull the iac off and try to clean it to see if it changes if so then there ya go!!! good luck

uvastang

hey man thanks for all the advise.... and any more that come in i can really use... but im not exactly sure that it idles normal at 1000 mostsly just below 1000 id say 850 or 900 but it still jus drops to 500ish and then back up.... and only in drive... not in park.. thats what got me.... but again thanks for any and all advise!!

mjr46

do what joel5.0 stated first then check for vaccum leaks and or clean isc valve