I have a 201 hyundai xg 300,my problem is the vehicle drastically slows with the ac on..30=45 mph

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2001 HYUNDAI

The starter motor will engage the gear in the transmission bell housing to rotate the engine, so it will be mounted on the side of the transmission. The illustration shows the XG-300 and XG-350.

if it is only no spark, check crank sensor and coil. the crank sensor tells the coil when to spark

It should be located beside the brake caliper either on front or rear wheels (not sure about side but surely on both wheels) will look like a small tube pointing towards the hub.

For 2002 Hyundai Sonata 2.7L MFI DOHC 6cyl check this procedure...
Alternator - Removal

1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
2. Remove or disconnect the following:
   Negative battery cable Radiator mounting bolts, 1.6L only Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator
   
   
   Fig. Exploded view of the alternator-XG 300
   

Removal & Installation

1. Before servicing the vehicle, refer to the Precautions section.
2. Remove or disconnect the following:
   Negative battery cable Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator

1. Before servicing the vehicle, refer to the Precautions section.
2. Remove or disconnect the following:
   Negative battery cable Radiator mounting bolts, 1.6L only Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator
   
3. Install or connect the following:
   Alternator and reposition the radiator, if raised Alternator wiring harness connectors Alternator drive belt
4. Adjust the alternator belt and torque the bolts to the following specifications:
   1. Accent: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 14-20 ft. lbs. (19-28 Nm).
   2. 2.0L and 2.5L Sonata, Elantra and Tiburon: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 105-132 inch lbs. (12-15 Nm).
   3. 2.4L Sonata: Pivot bolt to 26-41 ft. lbs. (34-54 Nm) and the adjustment bolt to 14-18 ft. lbs. (19-25 Nm).
   4. 3.0L Sonata and XG 300: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 11-16 ft. lbs. (15-22 Nm).
5. Install the radiator mounting bolts, if removed.
6. Connect the negative battery cable.

Hope helps (remember rated this).

Removal

1. Remove or disconnect the following:
   
   Negative battery cable Radiator mounting bolts, 1.6L only Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator

Fig. Exploded view of the alternator-XG 300 and XG 350


Removal & Installation

1. Remove or disconnect the following:
   Negative battery cable Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator
   


Fig. Exploded view of the alternator-XG 300 and XG 350

1. Before servicing the vehicle, refer to the Precautions section.
2. Remove or disconnect the following:
   
   Negative battery cable Radiator mounting bolts, 1.6L only Alternator drive belt Alternator wiring harness connectors Alternator. It may be necessary to raise the radiator
   
   
   
   Fig. Exploded view of the alternator-XG 300
   
   
   
   Fig. Exploded view of the alternator-XG 350
   
   
3. Install or connect the following:
   
   Alternator and reposition the radiator, if raised Alternator wiring harness connectors Alternator drive belt
   
4. Adjust the alternator belt and torque the bolts to the following specifications:
   1. Accent: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 14-20 ft. lbs. (19-28 Nm).
   2. 2.0L and 2.5L Sonata, Elantra and Tiburon: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 105-132 inch lbs. (12-15 Nm).
   3. 2.4L Sonata: Pivot bolt to 26-41 ft. lbs. (34-54 Nm) and the adjustment bolt to 14-18 ft. lbs. (19-25 Nm).
   4. 3.0L Sonata and XG 300: Pivot bolt to 14-18 ft. lbs. (19-25 Nm) and adjustment bolt to 11-16 ft. lbs. (15-22 Nm).
5. Install the radiator mounting bolts, if removed.
6. Connect the negative battery cable.

I hope hrlp you with this. Good luck and remember rated this help-

oxygen sensor

I've got no diagrams on this car but I'd check mass air flow sensor if you have one. Often they can be cleaned off and work well afterwards, or replace it.

Time for a little tranny work, maybe. How old IS that fluid? It's possible that it's time to replace or at least adjust the innards to get it up to snuff again. When you have the speed problem, does it seem that it is in low gear?

Hi! have a look at link below:
http://store.payloadz.com/str-asp-i.103789-n.2003_Hyundai_XG_250-300-350_Service_and_Electrical_Manuals_98_63_MB_Other_Files_-end-detail.html