545svk

Hi - with the intake and valve covers removed on my 87 S4, I'm wanting to test what else needs replacing while I'm in there.
To this, can I test the hall and knock sensors in any way, or do I replace them as a matter of course?

The connector on my hall sensor disintegrated, but that looks replaceable if the sensor is ok.

Thanks in advance

The Forgotten On

Only way to tell is with the car running. It will pull 6 degrees of timing if any of them are bad. Just unplug 1 and see if the car loses power. If it does, it means all are still good. If it doesn't it means at least 1 is bad.

Most generally replace the knock sensors when the intake is off and then others either repair or replace the hall sensor when the cam covers are off or engine is out.

You can see if they are working with a sharktuner, or a Bosch Hammer IIRC.

FredR

ST2 does tell one if the knock sensors and the Hall trigger are working but as I am aware [suspect] unless the LH/EZK are fitted with PEMs ST2 will not be able to read what is going on with stock chips.

Changing out the knock sensors whilst the inlet manifold is off is a no brainer if the ones installed are older than 10 years- that assumes one does not have the thing off every two minutes [as some of us do!!!].

I have just had my Hall sensor out- I feared the connector would fail- my fears were not necessary- turned out it had failed some 16 years ago and someone had pushed the male terminals into the female terminal and flooded it with silicon RTV sealant. ST2 tells me it was working OK so I reconnected it using separate junior power timer female connectors encapsulated in heat shrink sleeves with integral glue to seal. ST2 says it is working. If I have to disconnect it might be a bit tricky but worst case it will be snip job- I left the cable with additional length to accomodate a new connector in due course as and when.

Mrmerlin

I would suggest that you replace everything unless you like doing rework,
once cables shed insulation and the connector ends crumble,
then moisture will get into the wires and corrode them.
Then at the end of the day you can sit back and know that you have just performed a job well done.
and you should not have to think about these parts not working as they should.
Some might call it peace of mind.
Not replacing some of these parts could be called job security.

buccicone

What Stan said.

dr bob

It seems that the typical failure mode for the knock sensors is due to cable deterioration. Causes: Age, heat, oil/fuel contact, brake cleaner. The connectors are telltales but the real story is in the wiring and insulation. For the most part, the cabling is out of sight under the intake. The connectors and a few inches of cable is accessible/visible with minor tool work. Generally, the reasons for intake refresh or in fact having the intake off at all are the same ones listed above for the cable deterioration. So, in my opinion, it makes a lot of sense to replace the sensors and cables as PM; even if they haven't failed when you access them, they will before the next intake removal.

Two more things:
I was able to change the rear sensor on my S4 with the intake in place. There was some blood shared on the way, and while I had an intake refresh on the horizon, Rob's diagnostic tool shoed that the sensor had failed and there was some travel scheduled.

There are some available Bosch knock sensors with integrated connectors, something that opens the door to being able to replace the cable without replacing the sensor. It might then also be possible to change the cable without lifting the intake. The tool used to set the ISV connector might be just the right piece to do the small-space work under the intake. The Bosch sensor elements themselves are fairly consistent across the various cars, with the filtering and gating done in the EZK box. Piezo sensors can be scoped and responses compared to make sure a replacement like this could work.

FredR

Bob,

Interesting that you see cable deterioration- over here in our hot climate I see male junior powertimer plugs crumbling with the elecronic parts in good nick but not the female plugs albeit I have just replace most of them in my LH/EZK harness refresh. I have lost something like 3 knock sensors over the years and as I indicated in an earlier post in this thread I recently discovered that the male connector on the Hall sensor had vapourised and had a bodged repair presumably before I got the car 17 years ago but as per what I noted the thing was still working quite OK as indicated by the analytics of my ST2 kit thus why I worked the cores that looked in excellent condition. I replaced the CPS with a new one but I have repaired the old one with a new male plug- I was tempted to put it back just to prove that it still works but gave up on that one.

I have had cables in the engine harness go south but generally the cores in the LH/EZK harness stood up reasonably well- now I have new connectors on the MAF, the injectors, the ISV, the CPS, the idle and full throttle and an extension on the ISV with an additional outboard connector. I have tested the heck out of them to ensure I have them all connected and in the right slots!

Awaiting one part to arrive, fit and then good to go all being well!

545svk

It seems that the plastics and rubber used 30 plus years ago doesn't like the warm climates.
On my car it seems to be the mail plugs that disintegrate. Both under the bonnet, and on the brake ware and ABS sensors.

dr bob

I bundle the connectors into my "cable" definition. Trying to separate the cable and connectors from the failure of the sensor itself, and promoting the idea that a separate cable and connectors, as seen in other Euro cars with otherwise similar sensors. Just the cable and connectors could be replaced, with the possible option to do that replacement without lifting the intake.

PorKen

Knock and hall sensor error checking is a feature of the stock EZK code*. The ST is reading the state of the stock diagnostics via the stock diagnostic serial data lines so a PEM is not required.

Knock and hall sensor errors will retard timing at higher loads. All other monitored sensors are replaced with default values, Temp 2, calculated by rpm/load, WOT/idle, or ignored, shift pressure (auto) but do not alter the timing. (If there is no load signal from the LH the EZK enters a limp home mode of sorts, IIRC.)




* including early '87, but it cannot communicate any errors found with diagnostic equipment because it is missing the serial data coding

FredR

Bob,

The last two knock sensors that had the male connectors crumble were both working fine when retired and could conceivably have new connectors fitted. The Hall sensor currently ftted has been working with a failed connector for the last 17 years unbeknown to me- it will be interesting to see if it holds up now that I have spliced the cores. The CPS crumbling away was probably the reason for my difficult starting that we talked about- I fitted a new male connector because I had one to hand -whether it will work or not I do not know but it has gone in my bag of "fallback spares". In all cases the active cable cores in the shielded cable construct looked fine.

What I did note was that cables tend to get a bit frazed once they leave the body of the harness to go to the connector. All the old female connectors body wise seemed fine but not the same for cable ends where they entered the connector. Fortunately I was able to make correct colour coded pig tails harvesting wire from the original S4 harness I had with the exception of the fuel injectors for which I used new wire.

One would think the male connectors were made from the same material as the female connectors but seemingly not so.

FredR

That is interesting and good to know- even so not many folks will have access to ST2 if they do not have PEMS fitted. I know that even with PEMs fitted tthe stock diagnostics still work so I maybe it is no surprise that ST2 can read the status of those sensors even ifthere are no PEMs fitted. Must say I have never tried hooking up my ST2 to a non PEM computer and would not have contemplated such. Cannot say there is anything in the manual that advises against doing so.