This is on a '90 L98.

The other day I popped my right side exhaust manifold off to repaint it, this time without any clear coat. Reason being is that the clear coat turned some kind of dirty dark color the last time I repainted it.

Anyway, when reinstalling the manifold, I must have hit the knock sensor wire with it because I heard a loud pop which was obviously sparks that toasted the wire. The wire is still intact, but it's toasted pretty good.

Now my timing keeps geing retarded and the car is accelerating like crap.

I looked under there and the knock sensor wire is bare for as far as I can see.

I lose sight of where the wire runs because of the starter, and I'm not dropping the starter unless I have to in order to replace the wire.

Actually, I guess I should replace the knock sensor, too. Not sure how sensitive those are, it could have likely fried something in the sensor, too, when the manifold hit that wire.

Anyway..anybody know where that wire runs back to? The whole thing is bare, so gonna have to trace it back for a good foot at least.

I lose track of the wire because of the starter and can't see anything from above.

Need to find a place to splice a new connector into the existing wire up in there some place...

 

Knock sensor should be a DK BLU wire all the way to ECM Y11 terminal. It should be easily found if you look at ECM connectors to the appropriate conduit. 8A-20-5 for diagram I believe.

 

I'm not familiar with the way the dk blue wire is routed (I suspect that it goes into the engine harness with the other wires to the starter), but my 90 FSM shows that the wire goes directly to the ECM, Yellow connector, Cavity 11. Inspect the wire at the ECM connector, hopefully it is not fried at the ECM indicating that current reached the ECM.

The knock sensor wire does not carry battery voltage, I don't see how shorting the dk blue wire would fry it. My guess is that you touched the starter battery terminal with the manifold, and somehow the dk blue wire was also involved in the short.

 

Right. I just can't physically see where the wire goes beyond the starter to make a splice for a new pigtail connector.

Unless I remove the starter. Which I'd like to avoid.

 

I'd wondered whether I may have dinged the starter and caused the pop. It can't be just irony that this problem started right after that, though.

And I do have a code 43 now. And with the way it's running and the timing being retarded, I'm gonna replace the sensor and the pigtail.

I do know that the wire is blue, but as I'd mentioned the wire insulation is completely gone as far as I can see it up in there.

Just can't see the physical wire beyond the starter to find where to make the splice.

I'm probably gonna just have to drop the starter to see, I guess. Was hoping to avoid having to do that.

Will check that cavity on the ECM, though, thanks for that advice.

 

All of the ECM cavitiy wiring looked to be fine.

But...I had the idea to flip through some old pictures I took the first time I had the exhaust manifold off and there I was able to see what I needed to see.

Now I know and have a good visual of what conduit the knock wire runs through and where I need to splice it...



Hopefully a new pigtail will be long enough.

I can't see any of that from under the car and with the manifold installed, plus with the starter in the way, you can't see anything, it's all just feel.

The existing wire is bare almost all the way to where it exits the end of the conduit, though.

Might blast or sand and paint that rusty old knock sensor shield while I'm in there.

 

So, then, it looks like the best riute to take would be just to disconnect all of the starter wiring from the starter that is running through that same main coinduit that the knock sensor wire runs through, unplug the knock sensor connector, and then just drop the entire harness down to where I can mess with it on the ground.

That way I won't have to uninstall the starter itself.

Alright, then. I got it...

 

If you disconnect all the harness wires from the starter, you may be able to pull it up into the engine bay and work on it more comfortably from above.




^^ When was this pic taken? ^^ Because the pic is taken from above, with the manifold removed, I suspect that it is before the 'spark' occurred. Note that the wire is already bare.

With the blue wire's insulation being intact at the loom, it seems that the current went towards the knock sensor, I guess knock sensors have the potential to ground current. If this pic was taken PREVIOUS to the onset of Code 46, the insulation was already gone (possibly from heat exposure to the manifold???) and the wire got up against the starter or battery terminal during the manifold R&I.

While the forensics as to what happened are a curiosity, the bottom line is you have to repair the wire, replace the knock sensor, and say a little prayer that the ECM wasn't damaged by the introduction of 12V on the dk blue wire. Hopefully, the current went towards the knock sensor, and the ECM wasn't subject to full battery voltage; it went 'the other way' towards the sensor.

 

That picture was taken last year when I had initially removed the exhaust manifold.

I didn't bang into whatever I banged into with the manifold until I went to reinstall the manifold this second time that I had it off.

I'm gonna pick up a pigtail and a knock sensor and see how it goes.

I've never had a knock sensor code before now, so hopefully that's as far as any damage went.

No idea exactly what made contact with the manifold when I was fishing it into place, as I coudn't see. Only heard it when it happened.

 

6D5-5 Fig 4 gives you very good routing references for starter crank (PPL) and knock sensor wire.

 

If you would like to make your own pigtail in whatever length you end up needing! EFI Connection....Gray colored plug 100-01157....Black colored plug 100-01158. Link below for gray👍
https://www.eficonnection.com/home/S...ssSearchForm=+

 

That's a great idea. Was hoping not to have to make two splices to add additional length.

That link won't open for me, though.

 

That's strange, I even double checked it and it worked fine, but now it doesn't....this is the website, use part numbers from above, they have lots of great stuff!

https://www.eficonnection.com/

Edit: I actually have bought many of their kits just for the plastic plug/connector portion...I'll "release" the pins from the old connector and swap the new one right on...40 year old brittle plastic...gone! If your plug is still good, just get a new pin and seal for it and crimp that on your new wire.


kits come with an extra seal and pin.

 

For what it's worth, you could also consider using a single pin weather pac male/female connectors on the car side/other end of pigtail. Trace wire far enough back to get to "good" portion and crimp on the single pin female, have this connector come out of wire loom (electrical tape bands on both sides of loom where connector comes out) make correct length pigtail with male single pin on one end and knock sensor connector on the other. This would make the extension/pigtail "serviceable" and avoid the soldering vs crimp debate...I wouldn't think this would add anymore resistance in the line than soldering or a butt connector would...just an idea to consider👍

Edit: Almost forgot, I'm sure you have by now, but if not, it's time to unhook your negative battery cable before proceeding any further!!!!!

 

I would think any option you want should be available locally. An older NAPA here does many/most configurations. Not all do but many I'd think can help you or a parts vendor that does mostly fleets will have also. There should be no reason to do any shipping.

If there's a Fleet Pride local they surely could do terminals and probably connector shell.

https://www.fleetpride.com/

 

The picture of the single pin weather pac, was for reference, not suggesting the seller. I agree with suporting local businesses and I do....I will contend that a business like EFI Connection, needs to be supported by car people!!! If you've never looked through their website, take a look...many auto parts stores offer pre-made pigtails and such, but do not offer raw supplies for "building" wiring harnesses from scratch! Example below, sure Napa and all the rest could sell me TB pigtail connectors for my '84, but I didn't need/want a pigtail...just new plastic connectors...which I got for much cheaper through EFI Connection than paying for pigtail version local or not....Specialty businesses need our support as much as the local NAPA!

No pigtail needed!

 

I went with the 100-01158 and the one pin connector. I don't do Amazon so found that connector kit elsewhere.

Some wingnut on eBay wants 33 dollars for that thing, I noticed. Heh heh heh. I tell ya. Some people...

Something else I'm gonna do while I'm there is heat sheath the wire and all of the other wiring down there in that area, and as far up the main harness as I can get.

 

While I was waiting for my parts, I got the other stuff done that I wanted to do. Cleaned that knock shield up and repainted. Heat sheathed alll of the other wiring in that area, retorqued my exhaust manifold bolts at that front Y-pipe connection, and cleaned out my EGR ports, just because it's something I've been meaing to do anyway but hadn't yet done it.

Anyway. I rebuilt that entire pigtail and got it all back together.

I took it for a ride and no knock codes were returned.

Drove like a dream, too. I kept it mainly in second gear on the winding back roads and that was actually kind of fun. Got on the main roads and drove in third for a while. Accelerated really smooth, too, but still nice and raw and steady. Shift light blinked a couple of times arounf 55mph on the open highway, but I let off the pedal for a split second and it went off.

I'm liking driving in the lower gears better with this car. Also, Speaking of that, I forgot, I also retorqued all of my exhaust clamps. Which actually kind of restored a little power in those lower gears and sounded really nice. Good non-annoying rumble. No doubt they were leaking a bit before.

If I was in the Interstate I'd probably put it in fourth but I'm rarely on Interstate with this one.

Anyway. Yeah. So that's done. Thanks! Rebuilding the whole pigtail/connector guts and adding the in-line connector kept it clean with good continuity. I didn't change out the knock sensor itself, though. I wanted to see if the bare and partially toasted wiring and cnnector guts was the problem.

I do have a new knock sensor, though. I'll swap that out when I flush the coolant in the Fall.