Corolla pinging - old timing belt?

snipped-for-privacy@yahoo.com wrote:


Right!...everyone...DUCK!!!....
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-Gord.
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If that's the case, a top engine cleaner like GM used to sell would help. Have to figure a way to feed it through though, unless its a Throttle Body Fuel Injection system Tony
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It is probably not engine deposits and the Corolla does not have a throttle body fuel injection system.
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Ray O
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Dan wrote:

The pinging could likely be caused by either too advanced ignition timing or an inoperative EGR valve, or both.
Your 4A-FE probably has an EGR valve, but since I don't know what emissions package you have, you will have to tell me if it does. Emissions components are listed on the VECI label on the underside of your hood: look for "EGR". Or you can look for the valve under and behind the throttle body, or look on the vacuum diagram under the hood for it. I would suspect the EGR valve is plugged (if you have one).
You need to check timing too. I almost always find timing out of spec on OBDI Toyotas that fail our state's emissions inspection program. Use a paperclip or whatever and short E1 to TE1 in the small black diagnostic connector near the strut tower. Start the engine in park with the A/C off. Make sure your check engine light is continuously flashing about twice per second; any other behavior indicates a stored code or you didn't jumper the terminals correctly. Check the timing marks with a timing light. Adjust to 10 degrees BTDC (there's a large raised mark on the timing belt cover for 10 degrees) by loosening the two 12mm head ditributor holddown bolts and turning the distributor. If you can't get the timing to adjust to 10 deg. within the slotted adjustment range then the timing belt is probably one tooth off.
Toyota MDT in MO
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This engine has no tendency to spark knock.
Even a loose timing belt will not bring about spark knock (pinging).
Forget about carbon deposits and octane increasing additives.
DO verify the base ignition timing is set according to the EPA sticker under the hood.
The EGR system needs to be verified as functioning.
The EGR dilutes fresh air/fuel charge with exhaust gases. This has the effect of lowering the amount of heat generated during combustion and .... the tendency for preignition and detonation to occur.
The EGR delivery passage must flow lots of exhaust. The EGR diaphragm must be sound. The EGR diaphragm must recieve vacuum from the throttle body as the throttle is opened. The EGR transducer valve and bleed solenoid must be functioning as designed.
OTHERWISE, the engine will spark knock (ping) as you describe.
--

- Philip



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There's no EGR on my Corolla. I'll have the base ignition timing checked. Any idea why it may be out of spec? The distributor and timing belt have never been touched. Is it possible there's something wrong with the ignition advance? How does it work in this model?
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Got the timing belt and tensioner changed. The water pump had a leak where it connects to the engine, so I replaced it too. After this, there was some obvious bearing noise due to overtight accesory belts. I returned to the shop and mentioned this, and they confirmed the belts were too tight and reduced the tension. The car is still noisier than before (clacking from the valve train area) and it seems to have less power. Could it be an over tight timing belt? Is it possible to check/adjust this without taking apart a lot of things?
Tnx!
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Dan wrote:

Excessively tight accessory belts would not usually create a "bearing noise" immediately. They can *lead* to the destruction of bearings (even the front crank main bearing, if you're unlucky enough).
A clacking sound from the tbelt/valvetrain area would make me think loose tbelt, not tight. The belt could be hitting the plastic covers, or the slack could be causing a rattle between the cam drive slot and the distributor tang. Especially if the noise occured after tbelt replacement. Also, the new waterpump could be noisy, or the shop could have destroyed it's pulley during removal (it is a difficult pulley to remove if you don't know/care what you are doing).
Toyota MDT in MO
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Does this model (4A-FE) have a timing belt tensioner spring? How is the timing belt tension set?
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Dan wrote:

Yes.
You can turn the cam in the belt tightening direction while holding the crank to take the slack out of the belt, then assist the sprung pulley with light pressure, then tighten the pulley lock bolt down. Turn the engine over a few times and recheck belt deflection (this is where you use the service manual, experience, and common sense in equal parts). Redo the process if the belt is too tight or too loose.
Toyota MDT in MO
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Thanks!
Comboverfish wrote:

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