I was driving today finally got insurance, after maybe 30 or so miles the SES light comes on. You know what the car was doing? Its kind of done this before. When im cruising, and i stick it in neutral the revs will sometimes go down to like 400 rpm or so and jump up and down from 400 to around 1000 rpm, prob cause of the cam, no biggie. Sometimes itll stay at what rpm it was at before going in neutral and then SLOWLY go down to around idle speed, okay things are getting a little weirder, but everything still seemed fine driving wise. TODAY THOUGH when i put it in neutral it went to like 2000 rpm and STAYED THERE, BUT when i came to a stop it then did drop to almost idle (dropped to 1000 rpm, idle is around 850). Again, its done this before but not for so long like today, usually it eventually goes down to idle while im rolling or heaves back and forth like mentioned above, but this time it jus stayed at like 2000 rpm for at least about 1 min, maybe even like 2300, and the ses light has NEVER come on while driving before, this time it came on and stayed on.

I feel like it might be a sticking throttle cable maybe, but its just weird how when i came to a stop it seemed fine and dropped to about idle.

THEN, when i came home and parked it in the garage i rolled for a foot or 2 at a couple mph just to move it up a bit, then the idle dropped to like 2 or 300 rpm, again its done that before cause of the cam and eventually settles back to idle, but this time it actually made a quick hissing sound and then just shut off.

I turned the car back on, tried it again, slipped the clutch a bit with some gas, moved forward a few inches, let off the gas, press the clutch down and it dropped to really low rpms, made the really quick hiss sound and died. Like as if it dropped to too low rpms and it couldnt recover it or something.

Today was the the first time i drove the car quite a bit, other times it was just to like the exhaust shop or inspection shop then back home.

Any ideas?

Car is an 02 WS6 about 55000 miles, cam around 234/240 i believe 111 +2 or 112 +2 LSA. PRC 5.3L heads, full bolt ons, etc.

Other than the regular loud sorta high pitched sewing machine ticking noise our cars are known for, i dont hear any weird noises from the engine.

 

First thing to normally check yourself,

Is that the T/B and IAC port isn't gunked up with oil.
Once you know for sure these are functioning as advertised you can then start thinking about tune related stuff like Throttle Cracker, T-Follower and idle air.

 

yup, i was goign to say the same thing.

 

Ok guys the SES light shut off halfway through my driving yesterday and never came back on since.

The car was already all tuned before i bought it. The only thing changed on the car since i bought it was i extended the true duals out back under axle and i added high flow mettallic cats after the collectors before the x-pipe. As before, the car has front o2s but no rear o2s. Oh and right before i got the car i got the guy to raise the idle from about 650 to about 850 rpm or so. I should also mention its tuned for the 4.11s previously on the car but i now got 3.23s until i get a 9 inch.

The car keeps revving from about 500 rpm to about 12 or 1300 rpm when im in neutral coasting, unless i stop then it settles in a nice idle. Since the SES light came off it DOESNT do the thing anymore where it stays at like 1500 or 2000 rpm while coasting in neutral, instead it just keeps surging from 500 to about 1200 rpm, it wont do it a few times then settle into idle, it will keep doing it and keep doing it until i stop. This has to be KILLING my fuel mileage.

Do i need to buy a handheld tuner? Im new at all this stuff. Oh and the throttle body and IAC port is fine.

 

You really need to get hold of a tuner,

who knows his stuff to set up your Throttle Cracker, Throttle Follower tables mainly and probably a few other tables that control the IAC for all driving conditions.

 

yup, after doin a ton of searching, i keep seein the same thing mentioned, throttle cracker and throttle follower, thanks guys, its prob just surging cause of the big cam and heads, but if I can find a good rebutable tuner around here maybe ill get him to get a look at it. Im in the Vancouver area of British Columbia, Canada in case anyone knows.