Uphill accelerating issue

[pdiddy123]

I purchased an 03 Bonneville ssei in April. Since then I have changed the fuel filter, plugs and wires along with the other regular work to be done upon getting a used car. My problem is going uphill from a stop it accelerates find but upon letting off the gas it does not accelerate until I get over the hill. Can anybody tell me a good starting point to resolve this issue because I've been told it could be a number of things????

[RJolly87]

If you put your foot back on the gas, does it accelerate uphill then?

[pdiddy123]

It slugs up the the hill as the mph hours down

[nos4blood70]

You might also need to replace the coils and/or ICM. These symptoms are usually caused by an issue with the ignition system.

Taken from the Common Problems and Solutions thread:

Surging at 47+ mph while going up hills
Problem: You have a noticeable surge at 47+ mph while going up hills when the tranny is in OD.
Solution: While this problem feels like a transmission issue, 99% of the time, it is an ignition issue. There are 4 basic components in the ignition system: spark plugs, spark plug wires, ignition coils and the ICM (ignition control module) mounted under the coils. If you don’t know how old the plugs/wires are, replace them. Coils next, followed by the ICM.
Estimated Cost: NAPA Belden Premium Wires, $30-40
Spark Plugs (NGK TR55 or Autolite 605) (Never Bosch), $12-48
Ignition coils, used $10-15 each, new $30-70 each
ICM, used $30, new $130+

[J Wikoff]

If you put your foot back on the gas, does it accelerate uphill then?

[pdiddy123]

Thank you guys for your help! Replacing the ignition system components did the job :-) :-)