Cpasour

I have a 92 4x4 pickup with a 3vze and a 5 speed. This truck has been a pain in my a$$ and just when I thought I had all the bugs worked out more problems. It has a miss below 2000 rpm and getting code 52. Has new plugs, wires and cap. New tps and new KS pigtail. The cel goes off and on really runs like crap when the cel comes on runs fine when is off but still missing at low rpm if anyone has any helpful info to point me in the right it will be greatly appreciated. I just don't want to start changing parts that aren't bad

scope103

You probably have a wiring problem in the Knock Sensor circuit. When the ECM doesn't "hear from" the Knock Sensor for a few ms, it can't tell if the engine is knocking or not so dramatically retards the timing to save the engine. Retarded timing: runs like crap.

The obvious suggestion is to replace the pigtail, but someone already figured that out, and it either didn't help or was done incorrectly. The wire from the pigtail to the ECM is shielded, and if the wire has been damaged (breaking the shield?) enough noise enters the electrical system that the ECM can't pickup the KS signal.

If it were my truck, and I was somehow confident the pigtail was done correctly, I'd tease out the wire to the ecm and inspect it carefully. You could also have a bad knock sensor, but they don't often fail, and replacing it is a lot of work (as you know).

Good luck!

Cpasour

Would code 52 cause a miss at low rpm?

scope103

They're probably not related.

futcomker

Could be your TPS. Try testing and adjusting it before touching the knock sensor. Obviously test it first to eliminate it.
http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

From:
http://www.pirate4x4.com/forum/toyot...ck-sensor.html

"CODE NO. 52 - KNOCK SENSOR CIRCUIT
CAUTION: If ECM replacement is instructed in following testing,
always ensure ECM harness connector and ground circuit are
okay. If either are suspect, repair and repeat testing to
confirm ECM malfunction.
Circuit Description
Knock sensor is located on cylinder block below coolant pipe.
Sensor generates voltage when engine block vibrates due to knocking.
Code is set when there is no knock sensor signal to ECM with engine
speed of 1200-6000 RPM. Possible causes are:
* Open or short in knock sensor circuit.
* Knock sensor (loose).
* ECM.
Diagnosis & Repair
1) Ensure ignition is off. Access ECM behind right kick
panel. Disconnect ECM connectors. Using ohmmeter, measure resistance
between terminal KNK and ground. If resistance is infinite, go to next
step. If resistance is NOT infinite, go to step 3).
2) Disconnect knock sensor harness connector. Measure
resistance between sensor terminal and sensor housing. If resistance
is infinite, go to next step. If resistance is NOT infinite, replace
sensor.
3) Inspect circuit between knock sensor and ECM for open or
short. Repair as needed. If circuit is okay, substitute knock sensor
with known good sensor and retest. If Code 52 is still present,
replace ECM and retest. If code is no longer present, replace sensor.
CODE NO. 53 - KNOCK CONTROL CPU MALFUNCTION
CAUTION: If ECM replacement is instructed in following testing,
always ensure ECM harness connector and ground circuit are
okay. If either are suspect, repair and repeat testing to
confirm ECM malfunction.
Circuit Description
See CODE NO. 52 - KNOCK SENSOR CIRCUIT. Code is set when ECM
is detected to be faulty in regard to knock control. ECM is the only
possible cause.
Diagnosis & Repair
If any codes other than Code 53 is displayed, diagnose and
repair those codes first. If only Code 53 is displayed, replace ECM
and retest."