Rpm Drop When Hot

2002 Windstar I had the 171/174 codes and did the isolator bolt repair about a month ago. Van was running good until last week. After driving about 10 minutes when I come to a stop the rpms drop to 500 then surge to 800, the car lunges on accelleration. There is no engine light or code in the pcm. I turned up the idle screw but this only worked for a few days the pcm readjusted the idle. I took the cowl back off and checked all the vac lines I can find no leaks. Again this only happens after the car is hot and at a stop in drive. Im thinking an oxegyn sensor but i have no codes. Anyone have any ideas?

Well you will need to set the throttle adjustment back to where it was.. Then pull the IAC.. Idle air control valve off and clean it out.. 2 bolts hold it on.. Brake cleaner will work.. I do put a little WD 40 in it.. Just a little though. I have heard not to do that but it worked for me.. Try that and see what happens.. Sometimes the carbon build up causes the valve to stick.. Funny thing is a lot people on here clean there's to.. Had a parts guy say you can't clean them it better to replace. Well I have done them on Fords and Few chevys and never had a problem... Never.. I done quite a few..

Well you will need to set the throttle adjustment back to where it was.. Then pull the IAC.. Idle air control valve off and clean it out.. 2 bolts hold it on.. Brake cleaner will work.. I do put a little WD 40 in it.. Just a little though. I have heard not to do that but it worked for me.. Try that and see what happens.. Sometimes the carbon build up causes the valve to stick.. Funny thing is a lot people on here clean there's to.. Had a parts guy say you can't clean them it better to replace. Well I have done them on Fords and Few chevys and never had a problem... Never.. I done quite a few..


For some reason the forum won't let me edit... I said brake cleaner to clean IAC I mean throttle body/carb cleaner... Must have brakes on my mind.. But throttle body/carb cleaner will do....

Cleaned the IAC and still have the same problem. Thanks anyway garync1. Anyone else have any ideas. Again this only happens at a stop in drive after driving 10-15 minutes.

Rj,
Have you checked the EGR valve? It has been mentioned on this board that after some have done the isolator bolt repair that they have gotten an EGR code. Those symptoms sound like the same I had with my taurus. With that, I ended up replacing the IAC ( no change ), DPFE ( got better but not real good), then the EGR valve ( cleaning it didn't work). It ran much better after all this but in the end to get it to run perfect, there were two vac hoses that needed to be replaced.