idle surge
 

I just recently bought my 90 LX. It has a pretty aggressive cam(custom) in it. I have noticed lately that when started cold or warm, the idle will surge between 500-900 for about a minute. It won't stall, no problem after about a minute , and no stalling while driving.

My friend says it's pretty normal since the aggressiveness of the cam. I just want to see what others think. I was thinkin of checking out the TPS and cleaning the IAC.


eric

Consider yourself lucky. I have a mild cam...only the E-303....and I get random surging, except mine, if left to do it, will go from mild to severe surging and then choke and stall. I hear it's a problem with the IAB valve design being too restrictive. I think you can order a part from Ford that fits in between the IAB valve and has a screw on it that you can turn to let in extra air. I guess it works, but I've yet to try it.

But try cleaning the valve anyways, just to see what happens. Oh and I noticed you call it an "IAC" valve, instead of "IAB".....didnt use to own a GM by any chance did ya? ;)

Actually i noticed it is only when its a warm start. I havent driven the car past couple days and on start up it was ideling at 1200 and slowly dropped to 800 ideling fine. Went for a ride parked car and went to start it about 5 minut later and then it was doing the 500-900 for about a minute and then settled at 800, and fine driving. I havent checked anything yet, will hopefully tommarow or sunday.

That's EXACTLY what mine does. Cold idle is fine cause it's high, but when it's warmed up it'll surge. Like I said, at least yours doesn't get to the stalling phase. What I find will sometimes calm my engine down and keep it from surging is lightly tipping in on the gas until the rpms are at the top of what it's surging to...so if it's surging to around 900, say hold it at 1000 for 5 seconds or so, then SLOWLY release the pedal until you're off of it. That works for me sometimes--sets the car back into a normal idle pattern. If that doesn't work, killing the ignition and restarting it usually solves it for me too if it's a bad surge.

Check your timing.
I have the e-cam and it surges if my timing isn't advanced enough. I have to retard it to pass emmissions and then it surges a bit, even when I bring the timing back to where it was. I think the computer gets confused when I start moving things around. Mine mostly surges when it is cold.

Remember to reset your computer after making changes. Several times my surging has gotten better after resetting it.