How we doing guys I have a 99 sl2 and as the the thread says I have a blinking ses light. Now I know that means a multiple misfire and cat damage. what I don't know is why it's happening. Now the car runs great and I have replaced the plugs and wires both o2 sensors the fuel filter and the fuel pump is less then a year old. And I replaced the cat cause I thought it might be bad and that was the reason for the light but it still blinks. also it seems to only blink around 3000 rpms. Thanks for any input.

 

blinking SES means actively misfiring.

That's alot of parts to shotgun.

Go to Autozone or similar and get the SES codes read. It's free.
Post the codes (Pxxx, not the description) and we'll take it from there.

 

Alright man sounds good

 

So I am getting a p0300

 

The P0300 code means that a cylinder(s) is misfiring or is randomly misfiring. Start by checking for intake leaks, intake gaskets are common caused of multi-cylinder misfiring. If no leak are found the next step is to replace the spark plugs. If the problem persist more tests needs to be done to diagnose problem, see "Possible Causes".
Possible causes
- Faulty spark plug (s)
- Faulty ignition coil (s)
- Clogged or faulty fuel injector (s)
- Intake air leak
- Fuel injectors harness is open or shorted
- Fuel Injectors circuit poor electrical connection
- Ignition coils harness is open or shorted
- Ignition coils circuit poor electrical connection
- Insufficient cylinders compression
- Incorrect fuel pressure

Read more: http://engine-codes.com/p0300_saturn.html#ixzz2yGIMEhW5

 

How can I check for a intake manifold leak

 

Just spray some carburetor cleaner or even WD-40 around the intake. If the engine speed increases, there's your problem.

 

A P0300 is a random misfire and the cylinder cannot be determined. On the list above, one thing that is conspicuously absent is the CPK (crankshaft position sensor).

Is the misfire at 3000 rpms only or 3000 and up? Does it matter if in gear and moving or in neutral and sitting still?

If the misfire occurs in neutral, I would look at the CPK. If it only occurs under load, as in accelerating through the gears and it 3000 and up, then I would look to low fuel pressure due to a bad pump or clogged fuel filter.

 

I happens when it's above 3000 rpms but I have change both the fuel filter and fuel pump pretty recently.
And it's definitely not the crankshaft position sensor cause I just Change that.

 

Could still be the CKP if you bought it at your local Autozone, Advance, etc. They have the cheapest electrical parts because most are made in China. I know, because I used to work for both, years ago. I saw more failures on electrical components than any other thing. And, unfortunately for the customer, most electrical parts are not returnable once they've been installed. I'd suggest getting one from a Saturn friendly GM dealer.