Wouldn't we just try replacing it with another wire? If you can't at the connection point, then cut wires on ends, connect new wire between and check for continuity again. Luck.

 

You tell me--again, I'm a total noob when it comes to electrical work and wiring...

 

Let’s start off with WHY you believe you have bad grounds. List exactly all your FAULT symptoms and CONDITIONS. Also include any pending or active OBD2 MIL error codes and whether the MIL is illuminated on the Instrument Cluster.

 

Let’s start off with WHY you believe you have bad grounds. List exactly all your FAULT symptoms and CONDITIONS.

Pulsating cabin lights. Erratic idle on startup. Audible misfires from engine (sounds like an erratic muffled drumbeat), but no CEL and no codes at all. My theory is its extra detonation on the sparks causing the noise, but I could be wrong.

Plugs are new(er) Denso, from previous owner. Coils are Denso, but I'm not sure if they're original (274K miles). Knock sensors also newer from prior owner. Tubes are dry on inspection. I've also found and fixed two intake/vacuum leaks.

Previous/inherited 100A alternator was dying, groaning, and erratic; replaced with a 130A reman. and cleaned its electrical plug which had corrosion.

That's my best and most concise answer right now.

 

You could very well have multiple issues, both electrical and engine performance. They could be related or totally separate. Have you had your electrical charging system checked out by an auto parts store such as Autozone, Advance or O'Reillys? i would start there and have them verify your electricals, fix identified issues then move on the engine issues.

 

No, I have not. I frequent the stores but have never asked them for diagnostic assistance. When you say "checked out," what would they do, specifically?

 

As far as you ground issue that you have discovered, verify it by a visual inspection first ie broken or corroded or loose grounding lugs washers and bolts then move on to a resistance reading across the suspected attachment point. You should see nearly zero ohms across the connection.

 

The attachment point (circled in red in my initial photo) did/does appear corroded to me, though the perpendicular angle of the photo does not show the corrosion on the head of the screw. Could merely removing and cleaning it potentially solve that discrete issue?

 

3) How in the world do I locate (and access!) the other ground points? I've been following a ground diagram (also pictured below, plucked from an old post in our Forum), but it's so general, and I'm such an electrical noob, it's almost unhelpful for me. I'm also having trouble locating any kind of helpful ground diagram in my factory service manual.

The attached three pages from a 1999 factory service manual show the ground points for a 1MZ-FE Camry. Are you sure your Avalon manual does not have a similar illustration?

 

Thank you so much, Elle! My pdf FSM is separated into multiple chapters and, cumulatively, is many thousands of pages; so, no, I'm not certain it doesn't have it...but I am certain I haven't yet found it. Your attachment here is very helpful. Thank you, my friend! I appreciate you.

 

Update: I replaced the known faulty ground wire with a new strap, and essentially ALL of my electrical concerns and observed issues have finally subsided. Thankful!

That said, the "muffled erratic drumbeat" from within the engine persists. @Strega315, help me understand, broadly: what are some possible causes of that issue and noise? (I have taken video, but the camera mic does not pick up at all on those lower, muffled tones that are obvious to the observer. I've described the noise here as best I can.)

 

Does the drumbeat change with engine RPM or is it a consistent frequency? Does it sound like it’s in the top or bottom part of the engine, or completely external to the engine like intake or exhaust? Try starting your car and videotaping it from about 10 feet away so the louder, higher frequencies aren’t overdriving your mic audio. And see if you can narrow it down to a particular region on the engine. Uploading a video might be useful to other TN members whose ears are highly calibrated to Gen 3/4 engines and their sounds! Most of us have had our Toyotas 30-40 years or longer and know EXACTLY how they’re supposed to sound!

 

Update! I reached out to a professional mechanic and he's given me a compelling theory about noise(s).

Stupidly, for the first time and last time ever, I Seafoamed the car shortly after we bought it. Two cans. The noise started sometime soon after that treatment.

His theory is that some carbon that broke loose is hanging open one or more valves, even potentially an imperceptible fraction, and causing a partial misfire.

He also shared that, since I am still getting combustion, but just with low compression in one or more cylinders, I shouldn't have a buildup of unburnt fuel that could damage the catalytic converter. His advice was to drive it hard for a few hundred more miles and, hopefully, the problem will resolve itself.

I now liken Seafoam to this, bodily: breaking loose arterial plaque (good, in theory)...only to have it lodge in your brain and cause a stroke. I'm not a fan. I'll never buy or use any additives again--one and done for me.