What does this knock sensor test find out? Runs rich at idle.

Tiny
PCMENTOR29
  • MEMBER
  • 1985 TOYOTA PICKUP
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 75,000 MILES
Hi here is a knock sensor test I found in a manual:
1985-88 22R-E(T)
1. Warm-up engine to normal operating temperature.
2. Attach a timing light with advance indicator and a tachometer. Locate the Knock Control Sensor, (on the engine block), and ensure that the connector is secure.
See: LocationsSee Computer and Control, Knock Sensor, Location, Harness.
Fig. 210 Tachometer Hook-up

3. While operating the engine at 2,000 rpm, check the ignition spark advance and calibrate the timing mark to 0° TDC.
4. Using a wrench or small hammer, tap the exhaust manifold and observe the timing marks.
5. The ignition timing mark should move in the retard direction, depending on the intensity and speed of the tapping.
6. If the timing mark does not retard, turn the engine off and check the wiring between the Knock Control Sensor and the ECU.
7. If no problems are found, replace the Knock Control Sensor and repeat test procedure.
8. If timing still does not retard, replace the ECU.
9. Disconnect timing light and tachometer from the engine.

I did this test and could not get a responding retard spike. I noticed my advance on my timing light was around 40 deg to make it show at 0 deg on pulley. This was at 2000 rpm. This Toyota 22re runs a little uneven at idle(jumps from 750 to 740 to 760 rpm) and won't pass idle smog check. I have replaced the TPS in the past. My main interest is why does the timing not jump and if it doesn't why is there not a 12 code in the computer? What is the computer expecting to see from the knock sensor? Thanks
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Wednesday, June 18th, 2014 AT 8:04 PM

10 Replies

Tiny
HMAC300
  • EXPERT
If you get spark knock or any knocking noise the sensor sends a signal to the computer and the computer will retard the spark that is what it does. Your problem is probably something else. Check fuel pressure with a gauge auto parts rent it.
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Thursday, June 19th, 2014 AT 5:58 AM
Tiny
PCMENTOR29
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Thanks, so all the knock sensor does is retard timing, no A/F mixture?
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Thursday, June 19th, 2014 AT 2:22 PM
Tiny
HMAC300
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It does what I said it does
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Thursday, June 19th, 2014 AT 4:24 PM
Tiny
PCMENTOR29
  • MEMBER
I rented a Fuel pressure tool and will tackle Friday. Thanks.
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Thursday, June 19th, 2014 AT 5:45 PM
Tiny
PCMENTOR29
  • MEMBER
OK the fuel pressure is as stated in manual. 38.0 psi not running, 37.0 psi running no vacuum on regulator, 30.0 psi regulator with vacuum, and 35.0 psi after shut off for 5 minutes. I adjusted the valves because they were too tight and could not set idle a few months ago. I am using a heated O2 sensor on suggestion of LC engineering the maker of my headers. Plugs and wires, cap and rotor have less than 2500 miles on them. What could be causing the uneven idle which I believe is over rich? Thanks
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Saturday, June 21st, 2014 AT 7:37 PM
Tiny
HMAC300
  • EXPERT
What else is on engine besides headers? Has it been modified at all? Check for a vacuum leak.
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Sunday, June 22nd, 2014 AT 8:16 AM
Tiny
PCMENTOR29
  • MEMBER
Only headers and a K&N drop in air filter. Completely stock otherwise. What the way to check vacuum leaks? That works? Spraying carb cleaner on hoses and gaskets I can never when the engine surges. I haven't tried with tach connected. How much of an rpm surge should I look for? Thanks
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Sunday, June 22nd, 2014 AT 2:37 PM
Tiny
HMAC300
  • EXPERT
Ok clean your maf sensor, K&N filters with their nice oil are sometimes have to much oil on them screw u p the sensors in the vehicle. Other than that I have no further comments.
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Sunday, June 22nd, 2014 AT 3:29 PM
Tiny
PCMENTOR29
  • MEMBER
Can other experts still see my question or do I have to ask again in order to get more answers? Thanks
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Sunday, June 22nd, 2014 AT 5:09 PM
Tiny
HMAC300
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Repost your questionbut make sure to give all details so often people don't
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Monday, June 23rd, 2014 AT 6:45 AM

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