HESITATION WHEN ACCELERATING

SOURCE: 1999 Toyota Camry Idle Problems on Hot days

Clean the IAC. Disconnect throttle body air hose and you will see a hole on the bottom of the throttle body just before the butterfly valve. Spray throttle body cleaner down the IAC hole and then let it soak about 1/2 hour. Reconnect hose and run engine about a minute and then repeat this process 2 or more times. Toyota engines from 1997-2005 commonly have the IAC get cruded up with carbon as early as 35,000 miles. This is a sImple and cheap repair that many repair shops don't want you to know.

SOURCE: Hesitation on takoff and on acceleration

it could be one of many things with that many miles on the vehicle. when if ever did you change the fuel pump last? both filter and pump may need to be changed. that's alot of miles remember that. the filter is under the hood on the drivers side mounted on the firewall. under the brake master cylinder. be careful to relieve the fuel pressure before changing it.

SOURCE: P0450 CODE ON 1997 T100 V6 PICKUP. WHAT IS it and

Good day
P0450 is Evaporate emission system pressure sensor/switch
the cause could be
1. short or open in the vapor pressure sensor circuit
2.vapour pressure sensor
3. ECM

You can test with the following
you can access the ECM behind the glove box. turn ignition on,backprobe the ECM connector, on A/T models, measure voltage between terminals #1 (green/black wire) and #22 (brown/black wire) at the ECM E6 connector. on M/T models measure the voltage between terminals #1 (green/black wire) and #9 (brown/black wire) at ECM E6. if voltage is 4.5 - 5.5 volts, go to the next step. If the voltage is not 4.5 - 5.5 volts, replace ECM and retest.
2. back-probe ECM connector on A/T models measure voltage between terminals #15 (red/blue wire) and #22 (brown/black wire) at ECM E6. on M/T models measure voltage between terminals #4 (red/blue wire) at ECM E5 and connector #9 (brown/black wire) at ECM E6 connector. on all models disconnect the vacuum hose from the vapor pressure sensor. sensor is located near the brake master cylinder. connect a vacuum pump to sensor. if voltage is 2.9-3.7 volts without vacuum applied and 1.3-2.1 volts with .59 in.Hg (2kpa) vacuum applied. replace ECM and retest if voltage is not as specified go to next step.
3. check for open r short circuit in the wiring harness between vapor pressure sensor and ECM. repair wiring as necessary. if wiring harness is okay replace the vapor pressure sensor.

Hope this helps

Cheers

SOURCE: toyota rav4 2.0 d4d, hesitates on acceleration

Look at this thread -seems to be a cure for this problem.

http://www.toyotaownersclub.com/forums/index.php?showtopic=87986