I bought the car a couple of weeks ago its a 1999 Grand Am se 2.4 liter twin cam was running pretty rough in the get go. put new plugs n with correct ratio. and fixed it instantly car was running good for about 4 days and then engine light came on cylinder 4 misfire so I checked all the basics.pull spark plugs out one at a time clean them off. and when it was first cylinder 4 misfire what I did was put old spark plug in just to see plus not really having a lot of money even though they are cheap.. for the for spark plugs you get in a pk.& now it's cylinder 1 misfire not cylinder 4 misfire. starts up every time. Has hesitation on takeoff like it lacks power. when taking off from a green light it just the same thing for taking off any other time hesitation & lacking power...but what's weird is at highway speeds 50 to 60 miles an hour runs pretty smooth not bad but you go to speed up with throttle you feel hesitation at 60 miles an hour but if you're just cruising holding steady drives alright. What am I missing.

check version history, 99 to 05 and then 03 to 05 for coupe.

1999-2005 This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (November 2018) (Learn how and when to remove this template message) Fifth generation Overview Production April 1998-May 10, 2005 Model years Assembly Lansing, Michigan, United States Body and chassis Class Mid-size[34][35] Layout Transverse front-engine, front-wheel drive Platform N-body Related

• Oldsmobile Alero
• Oldsmobile Cutlass
• Chevrolet Malibu

Powertrain Engine

• 2.2 L L61 Ecotec I4
• 2.4 L LD9 Twin Cam I4
• 3.4 L LA1 V6

Transmission 5-speed Getrag F23 manual
4-speed 4T40-E automatic
4-speed 4T45-E automatic Dimensions Wheelbase 107.0 in (2,718 mm)[36] Length 186.3 in (4,732 mm) Width 70.6 in (1,793 mm) (1999-2000)
70.4 in (1,788 mm) (2001-05) Height 54.5 in (1,384 mm) (1999-2000)
55.1 in (1,400 mm) (2001-05) Curb weight Coupe: 3,066 lb (1,391 kg)
Sedan: 3,116 lb (1,413 kg)[37] Available in late spring 1998, the basic design of the fifth-generation Grand Am was shared with the Oldsmobile Alero (also new for 1999) and Chevrolet Malibu (introduced in 1996). The length was shortened slightly, but the wheelbase grew by more than three inches (76 mm). The suspension was now fully independent, with a revised MacPherson-Strut design upfront. The rear suspension is a more refined Multi-link design. The new Grand Am was offered in five trim levels: SE, SE1, SE2, GT, and GT1. The 2.4 L Twin Cam engine was carried over, with 150 hp (112 kW; 152 PS) and 155 lb?ft (210 N?m) of torque. GM's 3400 V6, previously exclusive to their minivans, became available as an option on the SE and SE1 and was standard on all other trim levels. For 1999, all the Grand Ams featured a 4-speed automatic transmission. The GT and GT1 also included 4-wheel disc brakes,[38] and all Grand Ams until 2003 included standard ABS and Traction Control (made optional on SE from 2003). The GTs also had a Ram Air induction system, providing an extra five horsepower and 5 lb/ft of torque over the 3.4 L V6 when installed in any of the SE-level trims.
The 2000 models added a Getrag 5-speed manual transmission as standard equipment with the four-cylinder. On GT models, the badge on the front fenders now read "RamAir V6", instead of "V6H.O." on 1999 GT's. ASC Creative Services designed the Grand Am SC/T for the SEMA show circuit, which was the concept design for the Ram Air hood and body package. The SC/T later became an appearance package, beginning in 2003. A road test by Car and Driver showed a 0-60 mph time of 7.7 seconds in a GT sedan with an automatic.[36]
For 2001, the SE2 trim level was dropped, a new family of Delco stereos and new wheel designs was introduced. The radio size in 2001 also changed from a 1.5 DIN size to a full 2 DIN size. Halfway through 2002, the Twin Cam 2.4 L engine was replaced by a new 2.2 L Ecotec four-cylinder, which had improvements over the engine it replaced, but produced less output; 140 hp (104 kW; 142 PS) and 150 lb?ft (203 N?m) of torque. Changes for 2002 also included a stationary cup holder in the center console as opposed to a removable one.
The body cladding on SE models was removed in 2003, a change which affected other models throughout Pontiac. Also in 2003, anti-lock brakes and traction control were made optional on the SE. In 2004, an MP3 player was added to the uplevel CD player. In 2005, Pontiac began phasing out the Grand Am lineup for the new G6 replacement. SE sedans were retained for fleet sale and GT coupes were the last Grand Am model available for public sale.

2003-2005 Pontiac Grand Am GT coupe The final Grand Am rolled off the line at Lansing, Michigan's, Lansing Car Assembly plant on May 10, 2005, shortly before the Lake Orion, Michigan plant began assembling G6 coupes. This was also the last car to be made at Lansing's old Fisher Body plant.
Available engines:

• 1999-2002: 2.4 L DOHC Twin Cam L4 (LD9 model) engine: 150 hp (110 kW), 155 lb?ft (210 N?m) of torque
• 2002-2005: 2.2 L DOHC Ecotec L4 engine: 140 hp (100 kW), 150 lb?ft (200 N?m) of torque
• 1999-2005: 3.4 L 3400 OHV V6: 170 hp,(175 for GT) 200 lb?ft (270 N?m) of torque (205 for GT)[39]

Available transmissions:

• 1999-2005: 4-speed automatic with overdrive (4T40-E for four-cylinder engines, 4T45-E for V6 engines)
• 2000-2005: Getrag 5-speed manual with overdrive (four-cylinder engines only)

It sounds like the brushes on armature for (blower motor ) are worn. Sometime a bad spot on the armature from not being used often and also by being in the engine compartment where it is exposed to condensation. When the brushes stop at that particular spot, the blower will not start spin process unless it draws alot of current that may be why the fuse blew. You can remove the blower and examine or just make the change.

Pull a plug wire and see if it is getting spark. If yes then hook a guage to the fuel shrader valve and check the fuel pressure. Just because you replaced the fuel pump already does not mean it didn't go bad.

replace spark plug and wire and if it has separate coil for the cylinder, change it.

you may want to perform a compression test on each of the cylinders,.
Best regards
Ck

Did you replace the plugs with the same plugs (Manufacturer) as the plugs you had in there. Some cars are very picky with plugs. ie: some Japanese cars will only run well with NGK Spark Plugs. Try to use only what Subaru recommends in your engine for the best performance.

Long shot, how about the air cleaner?

if is runnig the PCM is not the problem,change the coil pack or the crancshaft position sensor.
the PCM is very expensive(500+) but they hardly go bad. PCM(power control mudule)

one more thing,have you tried the spark plug wires?

Have you replaced the Fuel Filter Yet?

code 12 is start

13** No difference recognized between the engine MAP reading and the barometric (atmosphereic) pressure reading at start-up

Code 55 is end so 13 is all you need , basically your map isnt working
its an easy fix if thats all , take one off , put new one on