Need to Replace knock sensor and EGR temperature sensor

[MrMoody]

I recently replaced my fuel pump, FPCU, and MAF sensor last on my 92 Q because my fuel pump went bad.Afterwards I got codes 34 and 35 off the ECU. Can anybody tell me the easiest ways to remove and replace my 2 knock sensors and EGR temperature sensor? I have been getting some expensive quotes and can't afford to have mechanic replace. Thank you.

Jeff

[BCC93QT]

this one is a tough one. Your going to need to pull the plenum. Chances are if you haven't replaced any hoses your going to need to replace all of them. Replace the KS and KS harnesses, many clips and clamps, an entire rebuild of the engine is wise while your yanking everything off. Were talking 1200+ just in parts if you take the smartest route. That depends on how your injectors are as well. Now is the time to decide if you want to keep the car for say 5 more years... A good rebuild will result in significant longevitity if done right! Depending on the shape of your 1992 (interior and exterior)

[Q451990]

So you have a California emissions spec. car? Only CA cars had the EGR temp. sensor until the later years.

In any case, the EGR temp. sensor code indicates that the sensor isn't getting hot when the exhaust gases are supposed to be reaching it (e.g. when the ECU is telling the EGR valve to be open).

The port feeding the plenum from the EGR valve is a common area for carbon blockage - so your problem probably isn't the sensor itself, but a partially or fully blocked port. When you have your plenum off for the knock sensor replacement, remove the sensor and start chipping away. I like to use an old professional grade dental pick that I found in my dad's tool box years ago. Then follow up with a straight tooth brush, and sometimes a drill bit (not attached to the drill) that's just a little smaller than the port. At some point, with the help of a couple of cans of brake parts cleaner, you'll get that area completely clean.

I suppose it's possible to get the EGR port partially clean while it's still on the car, but it would be much more difficult. In this picture I have marked the EGR port's entry into the plenum with a red arrow, and the port where your EGR temp. sensor is located with the green one. You can see that it makes a 90 degree bend, which is perfect for trapping carbon deposits.



Here's a good plenum article. http://www.q45.org/plenum.html

While we're at it, do you know if your timing chain guides have been replaced?

Good luck!

Heath

[goody90q45]

.......Afterwards I got codes 34 and 35 off the ECU. Can anybody tell me the easiest ways to remove and replace my 2 knock sensors and EGR temperature sensor?.....Jeff

In the case of KS, the presence of a stored code can either mean they're working or they're dead. The KS code is often the result of some other component not functioning properly and the KS then do their job (retard/advance timing) and store a code which does not turn on the CEL. On the other hand if the KS are truly gone they'll throw a code immediately every time the engine is turned on, even after clearing the ECU codes.

Before pulling the plenum to replace the KS do an ohm test. It won't take 5 minutes. If they're reading outside the 550k ohm range they need replacing. If they're reading in the correct range some other component is malfunctioning, probably the EGR and its temp sensor. While you're there it's easy to also ohm test your injectors at the harness connector, another 5 minute job.



Heath is correct about the EGR passage getting clogged with carbon deposits. Clean the passage and the EGR valve and when you unscrew the sensor you'll see it caked with black deposits. It will clean up easily and your engine will run much better (without removing the plenum).

Let us know what you find.

[maxnix]

Read up on under plenum job. If you don't have incontrovertible proof it has been done correctly, it's time.

You don't want to do it two, three, four, five times because you didn't replace everything the first time.