Knock Sensor Location

[Butch_Cassidy]

Where is the knock sensor location on the engine?

[2seater]

On the rear of the engine, passenger's side, sort of above the oil filter adapter. It points straight back.

[Roadster90]

Hal .... 2seater,

Can you explain exactly what the "knock sensor" and or what it does please?

Thanks,

Nic

[padgett]

Knock sensor detects the rattle charactoristic of predetomation (ping) and retards the spark slightly.

The "OLD PA3" ED17 is a count of the knock cycles detected since startup and is common to get some when the engine starts and occationally some when you open the throttle suddenly. Operation on the edge of detonation is usually the most efficient.

OTOH a bearing knock or collapsed lifter will also trigger the knock sensor (try tapping on the intake plenium with a hammer while idling and you will probably see the count increase) and this will tell the ECM to retard the spark. MPG will suffer.

[Butch_Cassidy]

Thanks for the answer. Found it and replaced it. Now where is the ecm and how do i get to it. It looks like its behind the glove box but I do not know how to get to it.

[padgett]

The ECM is mounted vertically to the right (passenger side) of the glove box and to the left of the HVAC programmer (pull the black kick panel over the passenger's legs and you will see the bundle of HVAC vaccuum lines - they run right under the ECM which has three connectors - two black and one orange facing down. To remove the connectors, push the tab and pull straight down (may need to wiggle).

It's a pain to remove and even harder to replace. The carpet must be folded down and the HVAC line retainer removed to allow hose bundle to swing against the firewall and around the edge of the ECM. I usually knock off the vaccuum feed line to the controller when R&Ring an ECM. Removing the black post on the firewall side of the ECM before putting back in makes it easier.

The BCM is behind the glove box.

[Butch_Cassidy]

thanks padgett,

Also looking for the electronic spark control. Looked in the diagnostics and it does not seem to give a location.

[padgett]

The ESC is not a module. It is a signal sent from the ECM to the ICM (ignition control module under the coils) to advance or retard the spark.

[Guest ekvh]

So a leak or crack in the exhaust header could cause the knock sensor to retard timing and thereby reduce gas mileage? My 88 has a crack in the header/manifold on the number six cylinder, but it is in the direction of the knock sensor, so could the kerpows manipulate the sensor into thinking it is detonation?

[padgett]

Just look at OldPA3 (ED17). It increments when the knock counter senses something and should only occur on sudden acceleration, not at cruise or idle.

[Guest ekvh]

I just about have the header off now. One exhaust bolt I have to cut. I wish it was still on to see whether or not that ( the ED17 reading being tripped) is the cause. It could explain the significant drop I get with city driving shorter trips. I am guessing the crack is open enough when cold to allow a little air in and tells the O2 sensor to enrich. I will let you know if it helps after I get it repaired and run a tank or two. If it is, and I did read that the early headers were prone to crack more, that would explain some of the wide range of discrepancies in mileage except for lead foot syndrome.