Weird Idle and Engine shuts off for no reason?!

[Heavy-D]

I have been having 2 problems with my 92 GSX for the past 3 days. The first problem has been around since I got back from boot camp a month ago though. When the car is idling, it starts at 1,000 RPM and over 2 seconds surges up to 1500 and quickly back down to 1,000 RPM again. The second and more major problem is the engine has shut off 3 times on me. The first time I was getting on the offramp on the highway and I pushed the clutch in to cruise through the off ramp. Soon the engine shut off with no warning and I had no power steering or anything. Luckily I had not been going too fast and there were no other cars getting off. I applied the brakes and pulled off to the edge of the offramp, the car restarted with no hesitation when I turned the key. It happened twice more yesterday when I was having some fun on top of ice in a parking lot, I never revved the engine to high or gave the car full boost to be cautious and it still died.
I have only two explanations of why it might have happened and I was hoping someone more knowledgeable than me knows the answer. 1. My car was checked out by a mechanic while I was away and he showed me the old battery had covered some piece of metal with old corroded acid and so this metal piece is frail and only a fraction of the size it used to be and if it is severed, the car will not start. 2. I finally got around to modding my car and I had my manual boost controller set on 15 PSI, i then installed an intake pipe and I let a local kid who knows DSM's allot more than I do test it out. Suddenly the car was hitting 20 PSI on the aftermarket Boost Gauge, I then turned it down. So maybe my car was cutting the fuel when my engine died those 3 times because I thought the ECU remembers fuel cut or something like that.
Does anyone know what is happening to my idle, and more importantly, why my engine died 3 times?
I thank anyone for input and who takes the time to read my long description

 

[Heavy-D]

Anyone?

 

[steve]

Test your ISC. It's one of the causes of idle surge and also responsible for maintaining your engine speed. You need to measure the resistance of the coils (there are 4).

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Measure between 1 and 2, 3 and 2, 4 and 5, 6 and 5. The resistance should be about 28 and 33 ohms at 68F. If your ISC checks out you need to also make sure that your caps haven't leaked in your ECU damaging the circuit traces for the ISC.

Steve

 

[kalla]

My Talon shut off for no reason a few times. Then it shut off for good. The ECU was totally dead. Check the caps NOW ..

 

[Silver2GST]

Build yourself a Boost leak Tester (aka intake leak tester). The instructions can be found at www.vfaq.com or do a search for it and you will find lots of good threads. Too much air is entering the intake during idle and allowing the engine to rev up, until it hits the idle fuel cut at 1500 rpm (any time you have revs higher then 1500 and a closed throttle postion the injectors cut off to help slow the car down and turn back on at 1500 rpm to allow idle).

The stalling maybe related to this leak as well. Like others have said, a majority of idle and surging problems (among many other things) can be fixed with a leak test. Once you have fixed any and all leaks, if the problem remains i would agree that the ISC could be the problem and should be tested as posted above. and its not to hard to check the ECU, my 1990 Laser RS had a bunch of problems and alll were resolved with a new ECU.

post back with the results

 

[Heavy-D]

I would try the boost leak tester, but unfortunatly I'm leaving at 4:00 PM for Camp Lejeune, NC for who knows how long. I was thinking that since my dad was going to take my Eclipse to a shop anyway,it could be fixed while I'm away. What specifically should I tell the shop to look for?
Thanks for all the replies so far.