kenny_425

I have 02 GT 4.6 it has about 100200 miles on it and the oem coils were going bad. I replaced all of them with accel supercoils and ngk plugs. Now when I start it the rpm's hold at 3500 for a few seconds then drop and hold steady at 2300. I've looked for a vacuum leak and couldn't find a thing. Any other suggestions would be great.

tadpole1969

yeah sounds like vacum leak did you spray any starter fluid around air intake and so on if not do so itll idle up when u do this if theres a leak

Hangwire

Inspect your throttle body/cable assembly. Sometimes when I'm working over by the throttle body it can get hung up on some of my extra accessories back there. Make sure the lever that you can manually open yourself isnt hung up on anything. I forgot what it looks like back there without a blower on top but it sounds like your throttle might be hung up. If it isnt hung up you might try inspecting your throttle position sensor.

As has been suggested already it could have a vacuum leak but it must be a pretty major leak in order for it to cause this. Don't see how you could cause a vacuum leak like that by changing plugs/cops but I know I have to remove my air intake and TB in order to access cylinder #8.

kenny_425

I just install a new tps and iac and it made it worse by about 500 rpms. I didn't take the throttlebody off hangwire. I was able to get to everything just taking off the cai

kenny_425

Okay here's an update. A friend had a vacuum leak inspection machine. Have no idea what it's called. Anyway there was no leak anywhere. As I said before I replaced the tps and the iac. I also put the old coils back on and still the same problem. I put the new ones back on after the trial. I am the 3rd owner of this car and the owner before me gave me no info of anything done to the car as far as cpu mods go. So I'm wondering if this is a cpu issue. Any ideas?

kenny_425

new update. I just put a new maf sensor in and still the same problem. im losing my mind.

DeathRattle

Try taking the intake off and looking at the TB blade. While looking at it turn the butterfly and see if it opens all the way. Then release it and see if it shuts all the way. If you're unsure whether or not it is completely shutting then you can manually twist it to see if it is staying open a little. You will know it is staying open if you can see the blade remaining open or if you see a small gap between the butterfly and the stopper. If you manually turn it and it does close then try it again and see what happens. If everytime you release it it remains slightly open then you may have some gunk build-up on the butterfly and in the inside of the TB where the blade is. Sometimes a bit of build-up will keep the blade from fully closing. So if that is happening then you need to get some TB cleaner or brake cleaner and spay the inside of the TB and the butterfly. This will clean it and free the blade and butterfly up. Hopefully this will work. Sometimes when you get a brand new TB after some time it does build up carbon deposits. That happened to me with my 03 GT years ago. After I cleaned it out it never happened again.

Another thing to do is to let the engine run while spraying brake cleaner around the exterior of the engine. If you spray a certain area and notice the RPMs increase then that tells you a vacuum leak is present in that area. Because sometimes a vacuum tester could be incorrect.