Knock at low RPM - 3SGE

tomking · 07-03-2009, 12:23 AM

Hi all,

I am new to the MR2 and to this forum. Got a 91 MR2 non turbo and find that if I step hard on the accelerator at below 2500 RPM, the engine knock until it get above 3000 RPM. I replace all sparkplugs and still get the same problem. Check the timming and it is spot on 10 degree. The engine idle around 900 to 1000 but I guess it is normal for MR2. The Distributor looks very new, not sure about the Knock sensor because I cannot access to it.

What could be wrong? Does anyone here have similar problem? Could someone please direct me to the right area because going blind replacing parts are very costly as I just found out,

BTW: I have pushed the engine to 6000 RPM and it is running fine without any problem, strange that under 2500 RPM, it would knock regard which gear I was in if I step hard on the accelerator,

Thanks,

tomking · 07-06-2009, 05:49 AM

I disconnected the TPS and the car ran with 60% less knocking. Also when first started in the morning (cold) the car supposes to idle around 1800 RPM but it is not. I have to step on the gas to warm up the engine otherwise it would idle around 1100 RPM.

Any suggestion?

328FTW · 07-06-2009, 06:03 AM

Maybe its underfueling or doesn't have high enough octane in it and its knocking because without the TPS they generally over fuel more. They don't normally do that, what octane you running? Maybe it has carbon buildup on the pistons causing pre-ignition and such.

tomking · 07-06-2009, 08:12 AM

Quote:

Originally Posted by 328FTW

Maybe its underfueling or doesn't have high enough octane in it and its knocking because without the TPS they generally over fuel more. They don't normally do that, what octane you running? Maybe it has carbon buildup on the pistons causing pre-ignition and such.

I tried 95 octane today and it is still knock. Any idea?

MANDALAY · 07-06-2009, 09:13 AM

Does it in first gear ?
Ild try premium and BP . See if it stops.
Man use BP period.
You using correct spark plugs for sure ?
If still there take it for a full service at Toyota

328FTW · 07-06-2009, 09:21 AM

I forgot about plugs, you need plugs from the right heat range and gap it should be around somewhere what the 3sge uses the place you buy them should have the number anyway.

Just try some premium gas and some new plugs gapped right and if that doesn't stop it there is carbon buildup or/and a dead/clogged injector, you could try injector cleaner through the current gas I like to do that to cars when I buy them, you may need to get the injectors flow tested at some point if the problem persists.

palos · 07-06-2009, 10:43 AM

Just as an experiment, you could try retarding the timing to see whether you can get the engine not to knock. If it persists, you may have a problem with one or more of your spark plug wires, or perhaps the cap and rotor.

tomking · 07-06-2009, 05:16 PM

Quote:

Originally Posted by MANDALAY

Does it in first gear ?
Ild try premium and BP . See if it stops.
Man use BP period.
You using correct spark plugs for sure ?
If still there take it for a full service at Toyota

It knocks on every gear, will try the premium BP next but I for this old engine, I don't think it is required.

tomking · 07-06-2009, 05:17 PM

Quote:

Originally Posted by 328FTW

I forgot about plugs, you need plugs from the right heat range and gap it should be around somewhere what the 3sge uses the place you buy them should have the number anyway.

Just try some premium gas and some new plugs gapped right and if that doesn't stop it there is carbon buildup or/and a dead/clogged injector, you could try injector cleaner through the current gas I like to do that to cars when I buy them, you may need to get the injectors flow tested at some point if the problem persists.

Yeah, got the NGK indium Plug 23 buck each 0.8 gap.

Jason.MZW20 · 07-06-2009, 05:18 PM

Could be piston slap, but that'd be an awfully extreme case. My 1GR sounds worst between 1200-2500rpm, then smooths out after that. Sounds similar to rod knock, but it's definitely piston slap. Mine occurs most when the engine is cold, under load or not, and reduces in intensity as the engine warms. It's still there, but not as audible.

Might be worth investigating whether or not the pistons have been replaced. Some pistons expand at different rates, and some just sound terrible from poor fit, like my 1GR.

I'm running 10W-40 to reduce the issue, but I can still hear it.

I've heard that some 3SGEs have a piston slap issue, but I don't remember where I heard that from, so take it with a grain of salt.

tomking · 07-06-2009, 05:19 PM

Quote:

Originally Posted by palos

Just as an experiment, you could try retarding the timing to see whether you can get the engine not to knock. If it persists, you may have a problem with one or more of your spark plug wires, or perhaps the cap and rotor.

I did that and got less knocking, I am suspecting the Distributor, but how to test?

Jason.MZW20 · 07-06-2009, 05:26 PM

Quote:

Originally Posted by tomking

I did that and got less knocking, I am suspecting the Distributor, but how to test?

But the ignition timing is spot on 10 deg BTDC as you said. If the distributor had an issue, the ignition timing would jump even if the ECU diagnostic pins are shorted.

Plus, you'd be misfiring. It's the ECU's job to advance and retard timing based on signals from the knock sensor.

tomking · 07-06-2009, 05:30 PM

Quote:

Originally Posted by Jason.MZW20

Could be piston slap, but that'd be an awfully extreme case. My 1GR sounds worst between 1200-2500rpm, then smooths out after that. Sounds similar to rod knock, but it's definitely piston slap. Mine occurs most when the engine is cold, under load or not, and reduces in intensity as the engine warms. It's still there, but not as audible.

Might be worth investigating whether or not the pistons have been replaced. Some pistons expand at different rates, and some just sound terrible from poor fit, like my 1GR.

I'm running 10W-40 to reduce the issue, but I can still hear it.

I've heard that some 3SGEs have a piston slap issue, but I don't remember where I heard that from, so take it with a grain of salt.

Sound like an expensive problem to fix.

tomking · 07-06-2009, 05:35 PM

Quote:

Originally Posted by Jason.MZW20

But the ignition timing is spot on 10 deg BTDC as you said. If the distributor had an issue, the ignition timing would jump even if the ECU diagnostic pins are shorted.

Plus, you'd be misfiring. It's the ECU's job to advance and retard timing based on signals from the knock sensor.

You may be right, I don't get a CEL, no misfire issue so the Distributor may be OK. May be the sound of the piston slap.

Jason.MZW20 · 07-06-2009, 08:45 PM

Quote:

Originally Posted by tomking

Sound like an expensive problem to fix.

It shouldn't cause any long term issues. A lot of big bore V8s suffer from piston slap too, and they run forever. It may scuff the piston or cylinder wall, or it may not.

It's just annoying more than anything because it's not a sound you want to hear.

Try a thicker weight oil and see if it quiets down some. If it does, you've found your issue.

tomking · 07-07-2009, 02:05 AM

Quote:

Originally Posted by Jason.MZW20

It shouldn't cause any long term issues. A lot of big bore V8s suffer from piston slap too, and they run forever. It may scuff the piston or cylinder wall, or it may not.

It's just annoying more than anything because it's not a sound you want to hear.

Try a thicker weight oil and see if it quiets down some. If it does, you've found your issue.

Thanks for the info. The car still performing strong so I will leave it as it and run it for awhile see what happen. Any other suggestion is welcome as long as it is not costly. Most of my previous car being Honda integra including the DC5R and none of them having misterious issue like this one.

MANDALAY · 07-07-2009, 02:47 AM

Quote:

Originally Posted by tomking

Yeah, got the NGK indium Plug 23 buck each 0.8 gap.

Ild stick to platinum plugs.
BTW my run around car is a crapy 86 corolla. Couldnt be stuffed at tunning her. Anything less than BP premium and she knocks like hell

tomking · 07-07-2009, 04:00 AM

Quote:

Originally Posted by MANDALAY

Ild stick to platinum plugs.
BTW my run around car is a crapy 86 corolla. Couldnt be stuffed at tunning her. Anything less than BP premium and she knocks like hell

Friend of mine has the same Corrolla and yes, it does knock like hell

tomking · 07-09-2009, 05:21 AM

Quote:

Originally Posted by tomking

I tried 95 octane today and it is still knock. Any idea?

Hey, the knock is gone..... or at least I don't hear it anymore.

This is what I did:

1. Using Injector cleaner (over a week now) in the full tank of new fuel.
2. Rev the "living daylight" out of the car today for about 5 minutes on the Freeway on 3rd and 4th gear and ...wola... the knock has since gone.

I think it might be the injectors are now cleaned and sending enough fuel into the engine. But not to say it is fixed too soon until tomorrow startup.

328FTW · 07-09-2009, 05:51 AM

Cool remains to be seen but it might of just been crapped up injectors, not an unusual problem my 88SC went a whole load better after a good cleansing with injector cleaner and so did my old 84 it had a bad misfire which only went away after soaking the injectors in carb cleaner for 4 days then flushing with alcohol, it went sounded so much better when I was done.

07-03-2009, 12:23 AM	#1 (permalink)
tomking No Skills Join Date: Jun 2009 Location: Melbourne Australia Posts: 20 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Knock at low RPM - 3SGE Hi all, I am new to the MR2 and to this forum. Got a 91 MR2 non turbo and find that if I step hard on the accelerator at below 2500 RPM, the engine knock until it get above 3000 RPM. I replace all sparkplugs and still get the same problem. Check the timming and it is spot on 10 degree. The engine idle around 900 to 1000 but I guess it is normal for MR2. The Distributor looks very new, not sure about the Knock sensor because I cannot access to it. What could be wrong? Does anyone here have similar problem? Could someone please direct me to the right area because going blind replacing parts are very costly as I just found out, BTW: I have pushed the engine to 6000 RPM and it is running fine without any problem, strange that under 2500 RPM, it would knock regard which gear I was in if I step hard on the accelerator, Thanks,

07-06-2009, 05:49 AM	#2 (permalink)
tomking No Skills Join Date: Jun 2009 Location: Melbourne Australia Posts: 20 Thanks: 0 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Anyone? I've noticed that my TPS is not functioning properly I disconnected the TPS and the car ran with 60% less knocking. Also when first started in the morning (cold) the car supposes to idle around 1800 RPM but it is not. I have to step on the gas to warm up the engine otherwise it would idle around 1100 RPM. Any suggestion?

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07-06-2009, 06:03 AM	#3 (permalink)
328FTW Can you say grippy? Join Date: Aug 2008 Location: New Zealand Posts: 1,513 Thanks: 12 Thanked 99 Times in 83 Posts My Google Map iTrader Rating: (0/0% )	Maybe its underfueling or doesn't have high enough octane in it and its knocking because without the TPS they generally over fuel more. They don't normally do that, what octane you running? Maybe it has carbon buildup on the pistons causing pre-ignition and such.

07-06-2009, 09:13 AM	#5 (permalink)
MANDALAY Beams Owners Group Join Date: Feb 2007 Location: victoria AUSTRALIA Posts: 1,794 Thanks: 88 Thanked 63 Times in 59 Posts My Google Map iTrader Rating: (4/100% )	Does it in first gear ? Ild try premium and BP . See if it stops. Man use BP period. You using correct spark plugs for sure ? If still there take it for a full service at Toyota

07-06-2009, 09:21 AM	#6 (permalink)
328FTW Can you say grippy? Join Date: Aug 2008 Location: New Zealand Posts: 1,513 Thanks: 12 Thanked 99 Times in 83 Posts My Google Map iTrader Rating: (0/0% )	I forgot about plugs, you need plugs from the right heat range and gap it should be around somewhere what the 3sge uses the place you buy them should have the number anyway. Just try some premium gas and some new plugs gapped right and if that doesn't stop it there is carbon buildup or/and a dead/clogged injector, you could try injector cleaner through the current gas I like to do that to cars when I buy them, you may need to get the injectors flow tested at some point if the problem persists.

07-06-2009, 10:43 AM	#7 (permalink)
palos … Join Date: Apr 2009 Posts: 170 Thanks: 0 Thanked 20 Times in 18 Posts iTrader Rating: (0/0% )	Just as an experiment, you could try retarding the timing to see whether you can get the engine not to knock. If it persists, you may have a problem with one or more of your spark plug wires, or perhaps the cap and rotor.

07-06-2009, 05:18 PM	#10 (permalink)
Jason.MZW20 Torque Me!!! Join Date: Jul 2006 Location: Victorville, CA Posts: 875 Thanks: 12 Thanked 72 Times in 63 Posts Blog Entries: 6 iTrader Rating: (1/100% )	Could be piston slap, but that'd be an awfully extreme case. My 1GR sounds worst between 1200-2500rpm, then smooths out after that. Sounds similar to rod knock, but it's definitely piston slap. Mine occurs most when the engine is cold, under load or not, and reduces in intensity as the engine warms. It's still there, but not as audible. Might be worth investigating whether or not the pistons have been replaced. Some pistons expand at different rates, and some just sound terrible from poor fit, like my 1GR. I'm running 10W-40 to reduce the issue, but I can still hear it. I've heard that some 3SGEs have a piston slap issue, but I don't remember where I heard that from, so take it with a grain of salt.

07-09-2009, 05:51 AM	#20 (permalink)
328FTW Can you say grippy? Join Date: Aug 2008 Location: New Zealand Posts: 1,513 Thanks: 12 Thanked 99 Times in 83 Posts My Google Map iTrader Rating: (0/0% )	Cool remains to be seen but it might of just been crapped up injectors, not an unusual problem my 88SC went a whole load better after a good cleansing with injector cleaner and so did my old 84 it had a bad misfire which only went away after soaking the injectors in carb cleaner for 4 days then flushing with alcohol, it went sounded so much better when I was done.