EGR Question

[HKS1991]

Im currently throwing two engine codes: 52 & 71- Knock Sensor Signal and EGR system malfunction. Does anyone have any reccomendations? Does blocking the EGR cause these to be thrown? Or is it a failed EGR actuator doing this?

[Jeeves]

Well, do you have a california spec car? As far as I know, most Mk3's don't have anything actually monitoring the EGR, hence block off plates are hella easy to make and use. If it's a Cal.Spec car, I've never worked on that before.

As for the knock failure, that means you probably damaged the knock sensor wire and will have to rewire it. This is frequently done with Coaxial cable. If it's done w/o shielded cable you can expect it to run horrible.

Knock Sensor Re-Wire

[HKS1991]

Its a cal-spec but I dont have emission laws here. If I block the EGR do I have to fix it first? How do you block it? If I fix the EGR with the knock sensor stop throwing a code?

[movingviolation]

blocking your egr valve is really bad for the environment. there's threads about it, just do a search. I have a problem with my egr as well, & I have every intention of at least clearing out the built up carbon deposits in the tube that travels between the block & the valve. as soon as I have the cash, I'm buying a new valve & replacing my stock one. a properly working egr valve also has the added incentive of improved gas mileage. as far as I know, anyway - I could be wrong in anything I've stated.

[Jeeves]

Originally Posted by movingviolation

blocking your egr valve is really bad for the environment. there's threads about it, just do a search. I have a problem with my egr as well, & I have every intention of at least clearing out the built up carbon deposits in the tube that travels between the block & the valve. as soon as I have the cash, I'm buying a new valve & replacing my stock one. a properly working egr valve also has the added incentive of improved gas mileage. as far as I know, anyway - I could be wrong in anything I've stated.

Yes, all it does is take the exhaust gasses of the #6 cylinder and put them back into the intake. Please explain to me how disabling it is so horrific for the environment and how that affects your MPG.

I blocked the thing off, didn't notice a single change and didn't look back.

EGR Theory.

EGR serves one purpose and one purpose only. That purpose is to reduce Oxides of Nitrogen (NOx). Undernormal combustion, Nitrogen(N2)Oxygen (O2) in the air and Hydrocarbons (HC) in the fuel combind into water(H2O) Carbon dioxide (CO2) and the Nitrogen remains unchanged. Under very hot combustion temperatures, the Nitrogen reacts with the other two byproducts and forms Nitrogen oxide (NO). After being released into the atmosphere, it picks up another Oxygen and becomes Nitrogen dioxide (NO2). In the presence of sunlight,
it combines with other compounds like Hydrocarbons and forms Smog. Since exhaust gas is inert (very stable) it doesn’t burn again. So by being introduced into
the combustion chamber, it will lower combustion chamber temps enough so that
the Nitrogen doesn’t react with the other compounds and is passed unchanged out
the tailpipe thus not contributing to smog. Now, since exhaust gas doesn’t burn, it
doesn’t exactly help with combustion. At higher RPM’s, this really isn’t noticable,
but at idle, the reintroduction of exhaust gas will cause a very rough idle and can
cause stalling if to much is introduced into the combustion chamber.

That's the closest it gets to touching "really bad for the environment".

[HKS1991]

All I know is I want the engine light off, should I just fix it?

[albertmdh]

how can you tell if you'r ethrowing codes?

[Ne0z31]

easiest way to turn an engine light off is to remove the bulb... :-P

[bgrieger]

Actually, it does not operate at anything over part throttle...meaning no HP costs for better fuel economy and less smog emissions. The fuel part comes from the now higher air intake...the TCCS will match it with additional fuel when it sees it leaner than with the EGR.

[HKS1991]

Originally Posted by albertmdh

how can you tell if you'r ethrowing codes?

Engine light is on. Scan with a tool, or go to a mechanic.

[HKS1991]

Originally Posted by bgrieger

Actually, it does not operate at anything over part throttle...meaning no HP costs for better fuel economy and less smog emissions. The fuel part comes from the now higher air intake...the TCCS will match it with additional fuel when it sees it leaner than with the EGR.

I guess I do not quite understand? I understand it's function. With the knock sensor out it is advancing the timing, is this what you mean?

[Ne0z31]

Originally Posted by HKS1991

Engine light is on. Scan with a tool, or go to a mechanic.

what tool do you propose he scans it with? only place to get codes read for this year supra is a dealership since there isnt a scan tool than can read it...

just do the paperclip trick... easiest way to find a code

[Toysrme]

EGR system isn't opening. That is causing you to knock.

Fix the EGR, reset the ECU and see if the knock signal comes back. If it does you need to check the knock sensor.


1) Make sure the wire is clipped on TIGHT
2) make sure the knock sensor is screwed in


A new knock sensor is around $140 from toyota. Used ones go for 40-60 on ebay.

[Ne0z31]

jack one from a supra in a junk yard = free :-P lol

[bgrieger]

Knock sensors are completely seperate of EGR. Anyhow, 99.99% of the time, knock sensor problems are the wires, not the sensors.

You can get replacement knock sensor wires from Toyota. www.supras.com under the tech section to see how to replace them.

The EGR does not reduce power, and does reduce emissions and improves (fairly slightly) fuel economy. Most people falsely claim they get more power after removing it. It's untrue, as it does not operate all the time, but only at part throttle or idle. Find the EGR problem, fix it, and the code will disappear. Being a cali car, there may be an extra sensor I'm not familiar with.