98 gsx, won't idle

[GSEclipse620]

I've got a 98 gsx that, untill today has had the cel on. I got it read at advanced auto and it came up as a crankshaft position sensor code. It ran fine so I figured I'd just check it out when I got around to doing the timing belt on it. This is the weird part. Today the check engine light was out when I started it up to go to work. Great! That means 40 drive cycles w/o a problem right? Here's the good part. Now it does not idle.
??? No code? Obviously there is a problem, it's weird that the cel would only go out once the problem has reared it's head.

My only possible answer to this is that; ecu's learn the cars patterns right? Like long term fuel trims and make adjustments to the maps that are semi permanant aka;LTFT. Is it possible that it's been running w/o the ckn pos sens for so long it is now ignoring it and trying to run normally?

I'm pretty sure the only long term changes the ecu makes are to timing & fuel maps though so this theory is probably bogus, just trying to get the cogs turning.
Also, it runs fine all when it's not idling. Except for a couple of misfires under boost, but that's another thread... Thanks for any and all input!

 

[Gasolinebaptism]

Well it sounds like for some reason the battery neg. was disconnected, and if that happened it would have wiped memory, meaning that there will be no cel, and the car will try to run normally, using the CPS as it was made to be used, but it doesn't work anymore, thus ####ing up how the car idles.

 

[steve]

So the engine now runs but won't idle. Ignore that you had a code for a second and just focus on the idle issue. If the sensor is bad the code will come back.

Is the car firing on all cylinders?
Does it idle if you use the throttle a little bit?
Have you checked for vacuum leaks?

To be clear, did you just change the timing belt or did you do anything else too?

 

[GSEclipse620]

Well it sounds like for some reason the battery neg. was disconnected, and if that happened it would have wiped memory, meaning that there will be no cel, and the car will try to run normally, using the CPS as it was made to be used, but it doesn't work anymore, thus ####ing up how the car idles.

Good call, at lunch time the car wouldn't start, the wing nut had loosened up on one of the cables on my neg batt terminal Tightened her down. So I start up and I'm when I'm getting lunch I get a cel, go get it read. It is a P1105 which one thread told me was the fuel pressure solenoid. But it runs fine except for a little misfire under heavy load from 2-3k, think I just need to change my plugs. Could the fps be the cause?

The car does run pretty well over all but will not idle unless I'm on the throttle. My left foot braking is getting better though I found out when I read my code that ltft was at 0, meaning that the ecu did lose power and reset. I'm not sure if that would be related to this issue though or if they just happened coincidently on the same night It ran fine before the ecu got reset, not a lot as changed. So fp solenoid, eh?,,,

No, I haven't changed the timing belt since I've owned it. The original code it threw, which is why the cel has been on since I got it a couple months ago was for a crnk pos sens. It ran fine so I was planning on checking it out once I finally got in there to do a timing belt.