i will try to make this short. i have 92 civic coupe A/T i had swap to another D16z6 motor with low miles. when my tranny is in drive the idle drops about 300. when i am driving as i am comming to a stop or just coasting about 40 mph and my factory tach "once the needle hits about 1k the needle will bounce up about 1500 then come back down where the needl needs to be. Then it will do it again when i get down about 20mph. i have change my trottle body and idle control valve as well. any suggetions will be helpful.

 

search more? this topic has been brought up and solved a million times. But really, you'll probably find a lot of helpful information with some searching.

 

Search FITV or fast idle thermo valve.

 

I had a similar problem. Tried the IAC etc. Found that is was an air bubble in my collant, line. Pretty simple and inexpensive fix.

 

check the valve under the throttle body and check your IAC on the back of your manifold.. and make sure there are no air pockets in your coolant.

 

i have search all the fourms and i have tried pretty much everything. i have change out the whole trottlebody even the FITV, i bought i new IAC, made sure that i had no air in the coolant too.