52 code 1988 supra
 

Hello



New to this forum. I bought my daughter a 1988 supra turbo auto car that is now throwing a 52 code. It runs and idles fine. When it's going down the road less than 20 mph or shifting down into a lower gear is when it seems to run like it's missing. After a long trip if you try to restart if it's been sitting for like 30 mins it will start hard like it's rich. Any help will be great. I'm an old school muscle car guy so I know nothing on these cars.


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Code 52 is knock sensor. A Turbo car has 2 of them under the intake manifold on the block. A non-turbo car has one. A common problem is that the wiring harness for a knock sensors gets grounded. With my previous wiring harness I had to bypass the harness and run a separate wire from the knock sensor to the computer under the glove box shield. The way to test for this is to: unplug the sensor and run a test wire from the plug through a ohmmeter then to the plug on the of the harness that plugs into the computer (With the computer module unplugged). Look for an open or ground to the body. If there is continuity in the wire and no open or ground then check the other sensor harness the same way. Here is a link to a online supra manual that will give you the layout of the plugs that go into the computer.
On another note, check your vacuum lines to make sure nothing's unplugged. The routing for that is underneath the hood on a picture.

http://www.cygnusx1.net/supra/techtips.aspx


http://www.cygnusx1.net/supra/Librar...aspx?S=FI&P=50

KNK1 and KNK2 are in the middle plug.

I can't remember which one is #1 the front or the back. Is unlikely both are grounded. It should become apparent when doing the testing of both.
The plug comes off with a squeeze and I think its green. Be careful not to brake the sensor. They are expensive. I broke the one back by the starter with a socket extension when replacing the starter.

I just thought of something simple. Be sure that you have premium gas in the tank and that it's not old or stale. Regular gas will not run well in a Turbo engine and could throw a knock sensor code. If that's the case, put in a bottle of octane booster and top off the tank with fresh premium fuel. Drive it normally for a day to mix then pull the EFI fuse to clear the code 52. If the code 52 comes back, then more investigation into the wiring might be necessary.

It's either the knock sensor or the wiring that has a problem.