Scrubbing the engine ground cured two problems.
 

I pulled the main engine ground today. It was in very bad shape. It was covered in road grime and corrosion.

I unwound the multi-strands and saturated them with solvent and let it sit for 30 minutes. Rinsed it, and did it again with strong contact cleaner. Wiped it down. Scrubbed the terminal and the mount points.

Reinstalled, and drove the car.

Problem 1: alternator voltage barely registered at idle, and maxed out at 10 volts or so above idle. Now, at idle, it gives 11 volts, and shoots to 14 volts above idle.

Problem 2: misfire at idle, and rough running above idle. Anywhere in the RPM range, the engine sounded rough, like certain cylinders were not firing equally. This problem ceases to exist, and the engine sounds balanced and musical. Smooth as silk up and down the throttle range.

The car is running a little stronger now, and I feel that I'm getting closer to the sweet spot for timing and stoich.

I'm now feeling confident enough to switch to the OEM plugs like I said I would to see if I'm wrong about Pulstar plugs.

Tomorrow I'm going to pull and clean the alt's cables.

I plugged the lambda sensor in yesterday, and the car ran like crap. Question: what does the ECU actually adjust if I'm able to manually change the stoich balance? *confused*

Thanks to everyone for their sound advice so far. I'm having a blast tinkering with this fine automobile!

Where is this main engine ground you are talking about? Location?

:D

It's on the passenger side at the near-bottom of the engine. The ground strap connects directly to the body. No interference, it's right there.


SmileWavy

I'm sure you've all heard this electrical theory: electrons travel on the surface of the conductor, not through the conductor. So, by removing corrosion from the surfaces of all the strands in the ground strap, one can optimize ground's negative potential, thus lessening the load on the alternator. The energy it produces can be utilized equally amongst all loads without concern for discharge rate, especially spark plugs.

They travel through it too. Why else would you use large diameter cable to transmit heavy power? Instead you would use tiny wire and lots of them.

To the main point: did you also clean the other grounds? The electronics including the O2 sensor are grounded to the engine, which is grounded to the frame so-to-speak via the wire you referenced, and essentially to the neg lead of the battery. Gotta get them all.

If this is the ground from engine to frame then I do know this one. Either way, I'll locate it again and cleant it better. Thanks for the clarification.

Today I will focus on locating and cleaning the other grounds.

Regarding the theory of how electrons travel, I'm sure they do travel through the material, but considering how much of an improvement was made just by cleaning up the outsides of the wires, I'd say electrons prefer traveling on the outside.

:)

Maleficio, it occurs to me that your car should register around 14 volts at all times that the engine is running. A small drop is normal when you turn on the lights, but if you are having this much voltage change over the RPM band, then something is wrong.

-The voltage gauge on the instrument cluster isn't that accurate. It is good for trend information only. That is, if it suddenly is really low one day, then you know something is wrong. Your best bet is to access the battery, and using a voltmeter, test the system voltage at the contacts engine off and engine on. It should register around 12 volts engine off, and about 13.7 volts engine on, even at idle. If this is the case, then nothing is wrong but your voltage gauge is probably shot.

If it shows what you have mentioned, then either your alternator is failing or its' voltage regulator is failing, or some combo of the two. Clean all the contacts. Walley Pendley has a good write-up floating around the internet, and there is more info on the Nichols page. http://www.nichols.nu/tips.htm

Good luck!

N

Alright boys, I've got some interesting news for you.

Yesterday I pulled and cleaned the main engine ground strap, and had great success with voltage and cylinder harmony.

So today I figured why not go one farther and replace the ground strap altogether?

I went to a local car audio shop and asked them to make me a ground strap out of their heaviest gauge wire with the terminals soldered on and then crimped.

So, half an hour and twenty bucks later, I had myself a very nice ground strap covered in heat shrink.

So I get it installed, fire up the car, lo and behold, my tachometer works! It kept on working for the rest of day without fail, steady as can be.

I'm very excited about this because I was not looking forward to pulling the pod to fix the connections.

So then I decided to change the battery ground strap, too. I didn't see any appreciable improvement except for a slight climb in overall voltage on the gauge.

Oh yeah, the car now starts on the very first try instead of on the second or third try.

I read out both old cables with my ohmmeter, and they both showed perfect continuity. But just because a little ol' nine volts can find it's way through a cable doesn't mean that cable can carry a heavy load.

The main engine ground hangs VERY close to the exhaust down-pipe on the passenger side. I'm convinced this extreme heat is what ruined the cable over time. I don't expect my new cable to last very long, either. It's not made for this application, but served very well to uncover that big current limiter.

Pics:http://forums.pelicanparts.com/uploa...1273111448.jpg
http://forums.pelicanparts.com/uploa...1273111465.jpg

Thanks for the tips. I will check voltages tomorrow.

Maleficio >

Voltage cables can also corrode internally. I have seen many ground wires that were dust inside. You did good replacing that main ground. The strap in the rear usually is safe from excessive heat and wont deteriorate as fast as the engine ground.

Building on the subject, here's a battery groundstrap that needed replacing. Realize all that corrosion was hidden underneath a perfect layer of plastic sheathing. A problem that was totally stealth. And variable. One day it just gave up and I got only 3 volts to ground on a brand new huge battery, but 12.8Volts across the terminals. I had cleaned it many times. One day I got frustrated and slit the insulation open with a razor knife.


http://forums.pelicanparts.com/uploa...1273117633.jpg


Here's a bad ground --- engine electronics to block, same car. You can imagine the random symptoms I was having. No wonder the owner ditched the car. Easy fix:


http://forums.pelicanparts.com/uploa...1273117974.jpg




http://forums.pelicanparts.com/uploa...1273117839.jpg


http://forums.pelicanparts.com/uploa...1273118044.jpg


http://forums.pelicanparts.com/uploa...1273118088.jpg

Its not about heat. Its about moisture. Heat is one factor that accelerates corrosion when moisture is present. Salt is another rate changer. That battery strap was subjected to a little moisture leaking in from the quarter window and laying back by the connection point. Dcrasta, these are from an 85. If you haven't done it yet, when you do your fuel hoses under the air cleaner, under those is a pair of these grounds. They are crucual.

Wow, I am totally interested in this.

Sarcasm?

I'm really digging this. My tach works! :eek:

No, he is being sincere. But he lives in San Diego and there is no moisture.

Thanks for the pics, Landseer. Very eye-opening stuff. :)

This ground problem is not similar to F/A-18 wiring problems. So far, I've been approaching this car as I do a Hornet, and it's paid off, but this ground issue is a new realm of electrical trickery for me.

Hornets have tons of wiring problems, but it seems a bad ground is rarely the culprit. It's always shorts to ground, or broken wiring.

:cool:

Well, maybe that's true, but we've seen a number of rear grounds go bad. Time/temp/moisture/disimilar metals/electrolytic chemicals are all factors in corrosion. Dcrasta is keying in on the temperature. Interesting.

All that noted, this is really the first time I've noticed somebody has implicated that front stranded cable, outside of cleaning its ends.

I'm going to replace a couple and see if I can detect changes. It would be interesting to replace the cable and see less variability in voltage meter, for instance.

Or better yet the tach. I've got two that are intermittent.

Yeah, Chris is right. I am really interested in this. Did you just bring in your old ground cable to the stereo shop and have them make it to the same length? Also, I was thinking maybe adding a heat resistent layer to the ground near the engine. I use the Vulcanizing Silicone Tape in high heat areas. I used it on my Harness when I rebuilt it.

Good stuff:

http://static.summitracing.com/globa...or-72038_w.jpg

Moroso 72038 - Moroso Self-Vulcanizing Tape - Overview - SummitRacing.com