Hey guys I'm new on here. But I'll just get right too it. I've got a 92 RS 305tbi and sometimes, when i start it it will idle weird. It'll go up to about 2500rpm's then dip way down and almost die. It usually does this for almost a minute but then seems to clear up. But once on the road and you get into it, it still isn't real smooth. It doesnt seem to miss or cut out but its just not all that smooth when accelerating, almost like what you would expect from bad gas. But its got a fresh tank. Any suggestions on what it might be? Also I noticed the other night, after driving it on the highway for about 30 minutes straight, the service engine soon like came on, but after about 5 minutes it when right back off. Any help would be appreciated. -Thanks

 

Welcome to TGO!!


First lets check your codes, there is a port under your steering wheel, its 2 rows about 6-7 collums, looks like you can plug stuff in.


Get a paper clip, bend it into a U, with the car off, place this in a fashion to jump the far TWO TOP RIGHT pin holes, turn key to on, but dont start, first code should be 12

which will be like BLINK pause pause pause BLINK BLINK will do this 3 times, then the next code will shoot out. count how many blinks per long pause, you will get it after you do it, search for the codes on this site, or post em back up here and ill tell you what they are!

 

Will look like this

 

ok so i finally got around to doing this. And the first code that shoots out is BLINK BLINK BLINK BLINK. the second is BLINK BLINK BLINK third is BLINK BLNIK BLINK BLINK, fourth is BLINK BLINK BLINK. On the fifth time it is, BLINK pause BLINK BLINK. which it repeats three times just to go back to BLink BLink Blink Blink.

 

Ok so your car is posting a 43 x3 then 12x3

12 is normal
43 is not, gonna find 43 for ya right now.

 

43 says to be your knock sensor !

 

 

and if thats not your vin# here will list pretty much every code for everything !



http://www.troublecodes.net/GM/

 

hmmm.. thats probably not good then huh haha. But would that make it not run as smoothly??

 

The knock sensor in my '91 RS 305 TBI caused me untold headaches, but I never experienced what you describe.

 

Anything sending information to the ecm can cause problems, if your pulling that code, maybe you have a knock problem or your sensor is going haywire/fried

 

Ok, is there anything else i could check that might be making it not run as smooth or makes the idle go crazy sometimes? I've checked a few of the plugs (the easiest ones to reach) and they look good. But what i cant figure out is why sometimes when i start it it'll idle all weird but most of the time its fine.

 

If i was in your situation I would start from the beggining,
fix your code first, id simply get a new knock sensor
new plugs gaped properly
wires
new dizzy cap
PCV valve
Check all vacuum lines with carb fluid for leaks
Change oil
Check your timing make sure its not way off like 180*
Clean your TBI top to bottom, get a new gasket

 

might be a sign of your fuel pump going out, and an uneven air/fuel ratio can cause your engine to ping and throw a possible code 43.

 

Ok thanks for all the help guys. One other thing though, Why doesnt the service engine soon light come on and stay on if the knock sensor is bad?