2000 Gt, Stumble Upon Acceleration Or Low Rpm After Warmup

Car runs great when its cold but after several minutes of driving it starts to have issues with taking off from a stop, the longer it idles the worse it starts to sound, when I accelerate from a stop it stumbles and hesitates a little until I get into higher rpms, if I rev up the engine a couple times before taking off the symptom is reduced.

Once the car is moving it feels normal power wise even if I get on it.

On the freeway it seems fine but in city driving if I shift into 3rd or 4th to soon, or say for troubleshooting purposes take off in 2nd gear, the car bucks / hesitates like crazy, none of these symptoms occur when its cold.

Not sure what to check, I've had a couple ignition coils go bad before but usually I can tell what it feels like when its running on 7 cylinders vs 8, current symptoms seem different but might be worth noting 6 of the coils are still original (103k miles).

Car is stock.

Any ideas appreciated.
 
  • Sponsors (?)


For the sake of completion figured I'd update my post, It ended up being a bad COP in cylinder #4.

I pulled spark plugs and they looked normal (light tan color), Also checked fuel injector ohm readings with multimeter (hardly any variances noted) and finally checked ohms on coil packs (primary & secondary readings).

I did coil readings when motor was cold and again after being hot, the only coil that stood out in any way was coil 4 with a 5.11k secondary cold reading and all other coils read 5.36 - 5.45k ohms (meter set on 20k ohms).

Since #4 had the largest variance I took a chance and swapped it out with a new one (motorcraft), Car has been running great ever since.
 
Last edited: