Fermin4

Engine VZ-E 1995 4Runner with LACK OF POWER.

I has CEL 52 but Knock sensor does not present easy access since needs to remove intake manifold. CEL 52 appearance in the CEL depends to a certain point on changing setting of TPS and engine timing since I have tried some variation of setting and it seems to impact the time the ECM decides to report the CEL 52. Timing being the most prevalent. The more advanced the timing, the more time it takes to report CEL 52

Replaced: Head Gaskets 7 years ago. Run prefect until a month ago, All cylinders pressure tested above 150 PSI just now.

Early Symptoms one month ago: Engine died at traffic light but started OK right after that. CEL Codes:12; 14; 52 ;Air temperature; and MAF sensor.

What I did:
Replaced Plugs and Wires
Cap and Rotor
TPS
Igniter
Cleaned/ check Air filter, Fuel pressure at Fuel Rail; Scoped Secondary Ignition, Checked Distributor and G1/G2/NE signals; Vacuum signal at intake manifold on Snap Throttle; Removed ECM for Firewall and reset connectors. All of this are OK.
Car run better but lack of power with a sharp swing between 1700 and 1900 RPM if RPM if RPM are raised slowly. One half second period on oscillations for 1700 to 1900 RPM. Above 2000 RPM no hunting.

Questions:
1- How can I test MAF sensor with the Picoscope (2205A) to ensure there are no glitches.? (I do not have the Automotive Scope, need to set up manually)

2- where to hookup the scope to check with two channels for the impact of the Knock sensor signal on timing retard and knock sensor signals at the ECM.? Knock sensor wire should be shielded, can I remove part of shielding and use the core center wire for the Scope?

3- How to determine if the engine is or swings to Fail Safe Mode with the scope (only two channels available)

Thanks
I

scope103

First things first. You can't scope the MAF sensor, because you don't have one. You have a Volume Air Flow sensor, not a Mass Air Flow sensor. http://web.archive.org/web/201003261...92volumeai.pdf Different technology. But seeing as you're asking about using an oscilloscope, you may have actually worked on a MAF; testing a Karmen Vortex sensor (a type of MAF) probably would require a scope. But not your VAF. Follow the tests in the FSM cited, and add one more. Watch Vs-E2 as you move the vane with your finger. You want to see a smooth change in resistance, with no drop-outs or jumps.

Remember that when you have code 52, you are supposed to have a severe lack of power. The ECM, not having heard from the knock sensor, dramatically retards timing to save the engine. Retarded timing => runs like poop. If code 52 is not causing poor performance, your ECM is busted.

But since you have a scope and know how to use it, this might be of interest to you: http://www.parksoffroad.com/tacomamo...e/cip0325p.pdf The waveform is for a different Toyota engine, but the concept is the same.