Knock sensor error, car won't run properly - MR2 Owners Club Message Board
 
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post #1 of 11 (permalink) Old March 20th, 2017, 17:03 Thread Starter
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Knock sensor error, car won't run properly

I have reverted from the ECU Master EMU to stock ECU. Everything besides cams (HKS 264) is now original, it is also lacking the cold start injector stuff.

Problem: The engine won't run properly.

The engine was running more or less ok with the only CEL (Check Engine Light) being the knock sensor. It was "RPM hunting" until the IACV (Idle Air Control Valve) system was disconnected, then it ran more stable.

However, when attempting to start it again, the engine wouldn't start at all. It sounded as if it was running briefly on only two cylinders. no CEL errors at all this time.

The plugs were found to be flooded. It was also raining pretty heavily, and the car was left outside (but with the engine lid and trunk and everything else closed). After blowing the engine dry with compressed air and reconnecting the IACV, it started.

The engine runs too rich at idle. Then when giving it some throttle it responds extremely sluggishly, consistent with being too lean. The only CEL is now the knock sensor.

What the heck is going on?

Before reverting to the stock ECU the engine was very healthy mechanically speaking (and in every other sense).

The garage shop working on the car suggests buying a new knock sensor, but they have limited experience with Toyota. Is there any chance this could be related to the knock sensor? What will the stock ECU do if the knock sensor is disconnected? Will it go into safe mode? Will the ECU ignore it and allow the engine to work as if there never is any knock? Will it do something in between? Run with "safe" advance, but not in "full safe mode"? What does it do?

I'm asking this since obviously, if the ECU doesn't do anything but ignore the knock sensor, it might as well be disconnected and stay disconnected while debugging what the problem is, right?
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post #2 of 11 (permalink) Old March 20th, 2017, 17:29
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I know the knock sensor has to be connected and functional for stock ECU, otherwise it may assume detonation and pull timing. This should only occur when the other conditions are met though (ambient above 0C, engine temp > 70C and boost above 0psi) which excludes warm-up.

You mention running the 264 cams which will allow more fuel into cylinders which the ECU cannot control. This may be more of an issue than knock control.

jim
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post #3 of 11 (permalink) Old March 20th, 2017, 19:44 Thread Starter
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Thanks for the comments.

I'm using this oxygen sensor: NEW BOSCH OEM O2 OXYGEN SENSOR will fit LEXUS TOYOTA VEHICLES 13422 | eBay

Could it be a possible cause for the problem? Should I replace it with a genuine OEM oxygen sensor?
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post #4 of 11 (permalink) Old March 20th, 2017, 20:14
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Narrow band O2 has very little input to the engine running. It only effects idle and cruise mode. Could always try to disconnect and see if it makes any difference. Most of the narrow bands are the same so probably OK as long as its has the correct number of wires (ie sensor, ground and possibly heater element).

jim
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post #5 of 11 (permalink) Old March 20th, 2017, 20:26
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I've driven my car with CEL 52 for knock sensor, the engine idled and drove normally. The ECU was in a limp mode and wouldn't allow the engine to go over a certain RPM, I don't remember what it was but it was high enough that I could drive around town.

The wiring harness can be damaged on these engines which could cause error 52, you can throw the parts cannon at it but you'll most likely waste money. Jim is correct, your problems idling shouldn't be because of the oxygen sensor.

Gen2 ecu can idle although it will be high without the idle air control valve. You can disconnect the TPS as well, you can drive the car without it but don't expect the throttle inputs to be quick or smooth, the engine may drop abnormally low when you come out of gear from driving (like coming to a stop light) but you can drive without.

I'd go through the BGB and test the resistance for the TPS and AFM. You'll be fine without the cold start injector as well, the engine may take longer to start on abnormally cold days is all.
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post #6 of 11 (permalink) Old March 22nd, 2017, 20:33 Thread Starter
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Thanks for the advice. But if the AFM was bad, wouldn't the ECU give a different error code specifically for that?
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post #7 of 11 (permalink) Old March 22nd, 2017, 21:11
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I think what J Harris is indicating is that the AFM may be functioning but giving the wrong readings to ECU. There is a difference.

I must admit your fault description does sound like a faulty AFM sensor. Try and test according to the BGB and see if it passes the test. Having a MAP system I have never messed around with an AFM.

On the question of cams, have you successfully run the car on the 264 cams and standard ECU & AFM?

jim

Last edited by benckj; March 22nd, 2017 at 21:14.
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post #8 of 11 (permalink) Old March 22nd, 2017, 21:36 Thread Starter
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Quote:
Originally Posted by benckj View Post
I think what J Harris is indicating is that the AFM may be functioning but giving the wrong readings to ECU. There is a difference.

I must admit your fault description does sound like a faulty AFM sensor. Try and test according to the BGB and see if it passes the test. Having a MAP system I have never messed around with an AFM.

On the question of cams, have you successfully run the car on the 264 cams and standard ECU & AFM?

jim
I have only run the engine successfully with HKS 264 on the ECU Master EMU, I never tired running it on the HKS 264 before converting to the third party ECU.

Do you happen to know where in the BGB the test procedure for the AFM is? I see there is a test procedure in FI-131. Is this the test procedure you had in mind I should start with?
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post #9 of 11 (permalink) Old March 22nd, 2017, 22:04
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Originally Posted by diracdeltafunct View Post
I see there is a test procedure in FI-131. Is this the test procedure you had in mind I should start with?
That's the one, a long time ago you used to always see people damaging the AFM connector by unscrewing the screws next to the connector in an attempt to disconnect the connector. Is it possible that may have happened? I don't remember what would happen if the connector was damaged but this could be similar.

Just to make sure, you said everything was original, but you are using 440cc injectors correct?
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post #10 of 11 (permalink) Old March 23rd, 2017, 09:05 Thread Starter
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Originally Posted by J.harris View Post
That's the one, a long time ago you used to always see people damaging the AFM connector by unscrewing the screws next to the connector in an attempt to disconnect the connector. Is it possible that may have happened? I don't remember what would happen if the connector was damaged but this could be similar.

Just to make sure, you said everything was original, but you are using 440cc injectors correct?
I let a garage shop perform the conversion back to AFM, although they are not particularly experienced with Toyota I doubt they would make mistakes like that. But I can ask.

No, the fuel rail and injectors that are on it now should be OEM injectors.

I should perhaps mention that previously when the engine was running the battery light would come on AND the air bag light. This is a new battery. Since it has a leak and has been forced to sit outside I suppose it is possible condensation inside have corroded the connection to the air bag? Is that a common issue? Or is the combination of the battery light and the air bag light an indication of some other (possibly related) issue?
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post #11 of 11 (permalink) Old March 23rd, 2017, 09:55
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Usually when the alternator is bad the battery, cooling fan, and brake lights will be on. If it's just the battery light then you still have a problem, what's the battery voltage when the engine is running and not?

Airbag I assume is just an airbag fault, there's a diagnosis system for that as well.
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