4age 20v timing response to throttle

[gjgnz]

I'm currently trying to resolve a hesitation issue on a blacktop KE70. When I apply the throttle slowly the timing advances and the engine builds revs without issue. When I apply the throttle suddenly the timing retards momentarily, then advances and the engine bogs and sometimes backfires out of the throttle bodies. Is it normal for the timing to retard under sudden acceleration?

[ToyTA22]

I'm currently trying to resolve a hesitation issue on a blacktop KE70. When I apply the throttle slowly the timing advances and the engine builds revs without issue. When I apply the throttle suddenly the timing retards momentarily, then advances and the engine bogs and sometimes backfires out of the throttle bodies. Is it normal for the timing to retard under sudden acceleration?

Due to drop in manifold vacuum timing is normally retarded. Has it started this recently or has it got worse over time?
Backfiring usually is sign running lean, get injectors checked. May be enough fuel under light acceleration but not enough under hard acceleration, same as carburetor accelerator pump not working.

[gjgnz]

It's a new engine conversion so I haven't had it running 100% yet. It starts and idles perfectly but bogs badly when you snap the throttle. Fuel pump, lines and filter are all brand new. I pulled the injectors and soaked them overnight in injector cleaner, then replaced all of the rubber seals before re-installing. Not keen on paying $200 for ultrasonic cleaning unless I'm 100% certain they need it. The plugs definitely don't look like it's been running lean. Specs on the swap are:

4age blacktop
Stock auto ECU
T'weaked wiring harness
SQ Engineering Distributor relocation
Lift pump, surge tank and Bosch EFI pump

There are no fault codes on the ECU, ignition timing is 10 degrees BTDC, cam timing is correct as per FSM.

I would have thought that the TPS was the most important ECU input when the throttle is applied suddenly?

[jondee86]

Timing set with TE1 and E1 jumpered in the Check Connector ?

BT ECU has some "learning" ability, and needs to be driven on the road under a variety of load conditions so that the ECU can make some trim adjustments to accommodate out of spec sensor readings.

The MAP sensor is the primary load sensor, but the TPS is the sensor that initiates an "accelerator pump" type enrichment.

Cheers... jondee86