Toyota Ist - Intermittent Ignition Knocking Problem

[Tech Mate]

Hello experts,

I own a Toyota IST (2002) model. This model has 2NZ-FE VVTi engine (1300cc), driven about 85,000 KMs.

Couple of weeks back, it started making an occasional knocking-like noise and I realized this only happens between gear shifts (automatic shift), specially when i drive slow. To be specific, if I drive slow in traffic, when i slightly accelerate and when it is just about to shift from 2nd gear to 3rd, it starts with this rattling noise and after a couple of seconds it goes away. I never get this at idle or even if i rev up the engine and only happens when driven.

I wasn't too sure if the noise was coming out from the timing chain compartment, therefore I took my car to my regular mechanic which he overruled the timing chain after checking, suspected with knocking and advised me to try an EFI tune up which didn't make any difference. Then he suspected the knock sensor and/or the coolant temperature sensor to be failing intermittently, which i replaced them, still no luck. I also replaced the mass airflow sensor. I must say that it never came up with a "check engine" light and multiple scanning reports showed that tuning was right on and didn't indicate anything wrong.

After consulting many repair folks with no luck (which most of them confirmed that it was knocking yet unable find a proper cause), I finally decided to try my last resort - took it to Toyota for a full inspection of the problem. They opened up the hood, inspected the noise, had a test drive. Their diagnosis was that it is caused by a worn piston rings or a valve problem. They also did a compression test and confirmed that cylinder 2 has less compression (around 8:0) which the other 3 cylinders have the expected 10:5 ratio.

I don't consider myself a geek in this field yet I am not a dummy either. I do have some knowledge of how it works and what could cause what. Therefore, though my only lead is to go by Toyota's diagnosis, I would like to seek your expertise and opinions with regard to this before I go for an overhaul of the engine. Could a worn piston ring or values cause an ignition knock or a similar noise? I am truly worried if I would end with bigger issues if I don't fix it right now itself. It would be great to know if I have any other option and I am willing to take my car to any expert in this area.

Greatly appreciate your thoughts...

Note: I do not have any symptoms of oil burn and do not get any blue smoke coming out of exhaust. I also get good gas mileage. Didn't notice a timing miss either...

Thank you!

-Isuru

[invisibleuser]

Hi All,

I'm also facing the same issue except the sound occurring situation.

Mine is toyota vios and at cold start there is a ignition knocking. It only happens one time during the engine start. Garage person asked me to replace the timing chain. As far as I Know, timing chain is not needed to change (may be I'm wrong). Highly appreciate your comments.

[Rumesh88]

Hi All,

I'm also facing the same issue except the sound occurring situation.

Mine is toyota vios and at cold start there is a ignition knocking. It only happens one time during the engine start. Garage person asked me to replace the timing chain. As far as I Know, timing chain is not needed to change (may be I'm wrong). Highly appreciate your comments.

It cannot be the timing chain in a ECU controlled vehicle. Two factors that can produce knocking at cold start are the wrong IAT sensor reading and/or ECT sensor reading. Try resetting the ECU (with a scanner or with brute force method by disconnecting the battery for a few minutes) and see if the problem disappears. Or if you can get someone to scan the engine when it is cold (practical issue - either you have to do the scanning at your home or you have to keep the car parked overnight with the mechanic) for correct IAT and ECT readings, it should give you a clue. For example, if IAT or ECT gives a reading of 0C while the actual is 25C it can cause the ECU to advance ignition timing.

[invisibleuser]

It cannot be the timing chain in a ECU controlled vehicle. Two factors that can produce knocking at cold start are the wrong IAT sensor reading and/or ECT sensor reading. Try resetting the ECU (with a scanner or with brute force method by disconnecting the battery for a few minutes) and see if the problem disappears. Or if you can get someone to scan the engine when it is cold (practical issue - either you have to do the scanning at your home or you have to keep the car parked overnight with the mechanic) for correct IAT and ECT readings, it should give you a clue. For example, if IAT or ECT gives a reading of 0C while the actual is 25C it can cause the ECU to advance ignition timing.

Thank you very much for your detailed comment Rumesh88. I'll try the ECU resetting thing first and let you know the results.

[varunatech]

Sharing my two cents here.

The oil sludge in your engine has to be looked at carefully with professional advice. There are ways to clean, but an expert should evaluate before doing anything. Otherwise the situation will escalate.

For the engine pinging, sharing something which I have gone through and corrected practically.

There is a pre ignition knock (specially when applying load under slow speeds) observable. Usually a naka naka naka type of sound. And when you go up in speed and gears it goes away. This happens due to carbon deposits in piston crown and the some carbon particles becoming red hot. These red hot particles ignite the petrol vapor out of timing of the park plug. Result is pinging. There are many methods to get rid of this, and applies on how much of carbon you have. One of the easy way is to use a fuel system cleaner product, which is poured to the petrol tank. After treating with this for few times, some engines do come out of this. But you may use 95 Octane after that as lengthy use of RON 90 (where the engine is designed for RON 92 or above), any few other factors create this situation.

Have some thought on this and you may find some practices done by few people around the globe regarding the same issue. I did not mention the specific product which I did use. If you need can mention as well.

[Rasika19]

I have the same issue... can someone help me to contactthis guy (Tech Mate)???

[Rumesh88]

14 hours ago, Rasika19 said:

I have the same issue... can someone help me to contactthis guy (Tech Mate)???

Tech Mate is unlikely to respond because he has not logged in since 2014 October. What is the car in question in your case?

[kadsa98]

empty your tank and pump 95 octane. it's knocking because of pre-detenation. 2NZ-FE engine has a compression ratio of 10.5:1.

92 is therefore ideal for lower compression ratio engines (generally low performance engines with a *ratio below 8.5:1), whereas 95 and 98 (*Ratios between 8.5:1 and 10:1) are more stable and suitable for high compression engines.

Edit - ok i saw in the previous replies you have mentioned using 95 octane. ignore this then

Edited March 6, 2019 by kadsa98
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