Sparks coming from the idle adjustment screws?

Can't be normal right?

I decided to adjust the idle as she was idling warm at 1,200 RPM. I didnt know that the adjustment screws are hand tight. So I grabbed a wrench, waited for the fans to kick in and the wrench sparked when it made contact with the adjustment screw and the housing.

Good news is that I turned them clockwise (by hand) about .5 turns each and the car is idling much smoother now, just above 1,000 RPM.

Christian
1990 US TR

One more for the collective, my left hand window switch is forward of the left hand window switch on the center console. The Ricambi parts diagram shows them reversed. Kinda weird as they are different part numbers but i want to replace the right switch as it sticks in the Up Position.

Back to the garage.........

 

I think you mangled this unless you have two left hand windows

but they were probably (wrongly) swapped during some interior work -- easy to swap back.

 

Yea, the Drivers switch is forward of the Passengers switch. Haha Thats an easy fix.

Now what about the Sparks?

 

That's a new one for me -- if you use a DC voltmeter to measure between the air bypass screw and whatever housing you contacted (when the engine is running) do you get a significant DC voltage?

 

I just bought a volt meter yesterday so bear with me. I have the dial set at 20 on the DCV range. With one probe on the set screw and the other probe on the housing I get nothing. With one probe on the housing and the other probe on miscellaneous ground. I get .40. So that led me to believe that the whole housing was getting a current....same reading on the entire left intake housing..... .40ish.

When it did spark, the car stalled momentarily. That was enough to tell me dont try to recreate it again.

 

Seems too highish & strange -- are you sure that the braided groundstrap at the rear of the powerplant is in good shape/clean/tight/etc. on both ends?

 

Will check in the AM.

 

Couldnt wait, Ground strap was a little dirty. Pulled the strap, cleaned it, sanded down the ends to bright metal, same with the two washers and nuts.

Ill start her in the morning. Not too terribly concerned as there are grounding points on the lower intake manifold on the right side by the 7-8 fuel injectors.

 

Could the spark be simple static electricity?

 

If you had a very serious flaw in the grounding between the chassis and the powerplant, something probably would've melted during starter motor cranking, so I'll predict that this is going to be something a little off the beaten path.

Perhaps I should've first asked:

1. where exactly is this "other ground" that you are using, and

2. by "entire left intake housing" do you mean the 7-12 upper intake plenum?

~0.4V seems a subtle (yet unusual) fault if you are measuring between the 7-12 upper intake plenum and the chassis (but perhaps I'm misunderstanding what you are reporting).

 

Steve,
Do you think it would be a good idea to put extra ground wires on the engine?
Like a 10 GA. wire all the way to the battery.



Ago

 

Not a fan of that just for the added weight (and would need to be a much larger gauge to be effective), but also don't think that it's necessary (yet ) if the stock system is in good nick.

 

OK:

1. The 'other ground' I was referring to is between the 5 and 6 fuel injectors on the intake plenum. The 'other ground' was just an observation that Im assuming some current must pass through the plenum by design, as there is a ground for it. I wasnt using it for readings, just an Ah-Ha moment.

2. Yes, the entire 7-12 upper intake plenum.

Hope this clarifies things a little.

 

Steve is correct (and far wiser than I, on the 12VDC Ferrari systems) but you want the roiginal ground scheme 'working as designed" not a bunch of multiple paths..

I was really hoping (reading yesterday) that you found an unbolted strap.

Your symptoms are really two problems:

Where the potential is coming from.
Why it needs a ground.

Good luck you'll get it sorted!

 

Did you grind down to fresh metal also at the frame side of the connection?

There's also greases that improve conductivity.....fighting corrosion build up.

 

Not yet (your result implies that the components of the engine are at different potential, and that seems odd)

Are you saying that:

If you measure from the chassis to "between the 5 and 6 fuel injectors on the intake plenum" you get X volts, but

If you measure from the chassis and the 7-12 upper intake plenum you get Y volts?

Please advise the X and Y values...

 

For clarification, the "other ground"...
Image Unavailable, Please Login

 

Thanks Tim for the pic. I didnt measure the grounding point in the picture above, just on the left side upper and lower plenum. I have to give this a rest for the weekend as Ill be in Vegas for work. Ill take some more readings on Monday (or Sunday night if the wife doesnt see me sneak in.)

Christian

Good news, before it would idle about 100 RPM too high and bounce up and down on a cold start. After the adjustment the bounce is only a few seconds then 1,100 RPM.

 

I had my buddy over for dinner. He is a Senior Tech with Porsche (35 years) and we played with the volt meter. .01 max everywhere we measured. Cold, warm etc....nothing over .01. He was familiar with the fuel system and took readings off of the the alternator, engine ground, plenums etc. all normal. My readings were gone. Cant explain it, pulled out the wrench and no sparks/arcing at all.

 

That's usually best

The ground location shown in Tim's photo is where the engine supplies ground into the KE-Jetronic injection system -- it isn't another ground connection between the chassis(battery) and the powerplant.