99 Gt Power/idle/rev/vibration Issues

yellowgt99

New Member
May 26, 2015
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have a 99 by 4.6! First off when I start it it jumps to about 1500rpm then creeps down to 1000 and just hangs there. I put a new iac on and nothing. Second, while I'm driving around 40 mph my card starts vibrating I can feel it in the dash almost like its shuddering. If I floor it, I wants to go but it just kinda hesitates and stumbles so full power isn't there. I sometimes can smell gas as well. If I rev it, I sounds nice but sometimes it will bog for like 1/2 a second then rev up. i need help please! i have new plugs, I also have new radiator due to the oil trans cool breaking. Please any advice is great!
 
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have a 99 by 4.6! First off when I start it it jumps to about 1500rpm then creeps down to 1000 and just hangs there. I put a new iac on and nothing. Second, while I'm driving around 40 mph my card starts vibrating I can feel it in the dash almost like its shuddering. If I floor it, I wants to go but it just kinda hesitates and stumbles so full power isn't there. I sometimes can smell gas as well. If I rev it, I sounds nice but sometimes it will bog for like 1/2 a second then rev up. i need help please! i have new plugs, I also have new radiator due to the oil trans cool breaking. Please any advice is great!

Hey YellowGT! I had the same exact issue as you, and I replaced my coil packs and it solved the issue. I had new spark plugs and it didn't solve the issue cause it was the coil packs themselves. It caused my car to run rich and kind of bog down and hesitate a lot at WOT. Hope this helps! Good luck :)
 
Also I'd look into your o2 sensors I know when I had one go out my car ran a little cruddy and hesitated. But you should have a engine light if that's the case. If no CEL then go straight for the packs as CamronM stated.