drisin80

i had an interesting thing happen when starting the car yesterday. after completing numerous projects-- went to fire the car up and heard a violent backfire. checked in the engine compartment, and all (i mean all) of the intake hoses were blown off. all six vertical both banks, and all horizontal ones as well. i checked for this problem on the search mode here, and found a couple of similar occurences. anyway-- removed blower motor, and air filter for access and went about reassembling. not too big of a deal-- took a couple of hours--- but it seemed to me that none of the hose clamps was particularly tight to start off with. after reassembly-- with some trepidation--fired it up again. runs fine with the exception that the idle speed is 3000 rpms. i figure that this is an idle control valve problem (caused by the backfire???). could be something else i guess. i read in another thread that this is the idle speed when the idle control valve is stuck. if this may be the case; is there any way to unstick it. anyway--this should have made for interesting reading. any ideas about the idle control system would be greatly appreciated.----------tom

drisin80

by the way-- this is a 90 c4.

Geoffrey

Check the spark plug wires and make sure they are wired properly and in the correct firing order for both banks.

drisin80

not the problem--- didn't change any of that--- and runs fine now. just the idle speed problem. thanks

Indycam

Do you have the stock air cleaner box ?

dfinnegan

The ISV is easy to remove and clean. Have you looked at it yet? You should be able to see the mechanism within and hear it move when you roll the unit between your hands.

The shuttle in this pick moves to the left. That is, it moves to close the gap and then moves further to open the gap all of the way.

Many thanks to the Rennlister who originally posted this pic!

drisin80

thanks for the pics. indycam---stock airbox. -tom

drisin80

by the way-- has anyone ever heard of this getting stuck open???

Indycam

Stock air box , when its running , put your hand over the air intake horn , slowly choke off the air flow and see if it still runs or if you hear a leak .

drisin80

if i put mu hand over the intake horn--idle slows somewhat. cannot hear any leaks. not sure if this is a good test as i have a k&n filter in it which is supposedly the right one, but doesn't seam to seal perfectly. with my hand over the horn, can feel air being pulled around where the filter is supposedly sealing. are you thinking i have a leak elsewhere??? also pulled the idle control valve-- inner part seems to move without any problems.

Indycam

"are you thinking i have a leak elsewhere"
You had an explosion that blew apart your intake system , so its not unreasonable to think it maybe has a leak .

"where the filter is supposedly sealing"
Is dirty air getting sucked into your engine ?

If you pop the top off the air cleaner and remove the filter , if you stick your hand over the inner air horn , can you kill the motor or hear an air leak ?

drisin80

indycam--- will check tonite. any chance that i could have changed the throttle position when reattaching everything--lot of movement when the intakes were loose.

Indycam

Yeah , check see if the thing does close . Wishing I thought of that .
Now that you bring that up , I wonder if the air flow meter wiper got whacked by the big bang ?

KirkF

To repeat what has been said above, my first guess would be you have a vacuum leak.


Kirk

drisin80

throttle fullly closed at idle??? how can i tell??? won't get back from an 8 oclock meeting till 9:30 or so. will check if i still have the energy.-tom