just changed the opti and spark plug wires a couple weeks ago car ran fine then started to get a slight studder to it occasionally. went to drive it yesterday and car studders real bad, really noticible like below 2000rpm the car like shakes a little. then if you step on the gas it kinda smooths out but still isnt running right. then the check engine light comes on if you just drive it slow the light will come back off but then comes back on when you get on it again. in park its not as bad. the car is a 94 z28 112,000 miles

 

check for any vacuum leaks on your intake.

 

changed the plugs and wires tonight no difference had someone go for a ride with me noticed a whining noise coming from rear of car but no stereo in the car right now he went back and checked said its coming from the fuel pump first off is there supposed to be a whine coming from it then he said that it could be a fuel injector also im not sure im just geting real frustrated with the car..

 

Scan it for codes and find out what is turning on the SES light..... might point to the cause of your problem.

 

New here but might be able to offer some help. Have you checked your EGR valve?

I had a Caprice with a studder that turned out to be a bad EGR valve. After replacement, all fixed!

 

i brought it to a shop to get it scanned he said that since the light wasnt on right now that it wont tell him whats wrong. how would i go about testing the egr valve? and also is the fuel pumps supposed to be so loud inside its annoying me ?

 

If the light has been on in the past, the code should be stored in your memory.

I am not entirely sure how to check for a bad EGR. I was told to replace it by a friend and it got rid of my studdering.

 

ok i checked the egr valve books says put suction to it and it should die down wich it does meaning that the diagphram is working. next says to check solenoid got suction going to it but nothing coming out of it under throttle either. checked the power going to the solenoid no power, whats my next step ?

 

The EGR only works when the engine is on the road, under very specific load conditions. The solenoid isn't going to open if its sitting still and you are revving your engine.

The code is stored. Find a "shop" that knows the basics.

 

read the book all brown wires went to the airpump relay switched that and got power to the egr solenoid.

 

took car for a ride runs better but still not quite right

 

that whine coming from the rear of your car isnt the fuel pump its probably your differential

 

I've read this "sentence" 10 times and have no idea what you are saying?

 

its not the differential it wouldnt whine in park.

the wires that go to the egr solenoid are brown and gray, i followed where they went in the manual and all the brown wires lead to the air pump relay. i switched out the air pump relay and then i got power to the egr solenoid which i wasnt before.

 

In a 94, the brown wire to the EGR solenoid comes from fuse #6 in the underhood box. The power to the AIR pump relay comes from fuse #7 in the underhood box, via a brown wire. They are not interconnected.

So... after this breakthrough, did it solve the stuttering problem?