91vert

First of all, don't flame me right off the bat for not doing a search on this topic...because I have and I didn't find what I was looking for.

My 91 NA vert (no mods) runs fine with the exception of some slight surging at cruising speeds. I don't have the 3800 RPM hesitation, but I am wondering if a flakey ground could be causing the surging.

I have bought some 4 guage wire and some connectors to replace the cheesy braided ground cable that goes from the lower intake manifold to the firewall. Half of the insulation is gone off of it and it just doesn't seem to be substantial enough.

Where else have you guys placed additional grounds under the hood, or where else are the stock grounds? Are there some grounds that just need to be cleaned up?

I have seen some mention on other threads about regrounding the ECU and one from the exhaust to the chassis?? What is the point of the one on the exhaust, and what is the best way (where to connect) to reground the ECU?

Amur_

I got a little happy with ground wires on my NA FC, both help my alternator and to chase the 3800 stumble (which I finally did eliminate.)

Using 6-gauge automotive wire (make sure it's the multi-strand automotive wire - don't use anything else - and don't use anything smaller than 10 gauge) I installed a ground wire:

1) from the negative battery terminal to the chasis (the outer bolt holding the master fuse block in place on front of the strut tower.)

2) from the alternator's tension adjusting bolt to the battery's negative terminal.

3) to replace the ground wire on the backside of the engine (running from the tranny housing to a nut up by the wiper motor.)

4) on the ECU harness in the passenger footwell. But this was a 3800 stumble fix and may not be for you. I don't have the desc. in front of me but a write-up does appear in a few FAQs out there... Also added a ground at the air boost sensor for the 3800 fix (which was what finally nixed it.)

5) to replace the main engine ground (from behind the plugs/under the oil filter to the chassis.)

6) from the y-pipe (where your exhaust splits to go out to your mufflers) to the chassis. There's supposed to be a factory ground there, but 15 years on the road tends to nuke them.

I've read mention of people who suggest adding a wire from the alternator output to the battery's positive terminal to parallel the stock wire and make the alternator's job easier. I've asked around about this, and the general consensus was that doing this is a gamble. You risk cooking some/all of your RX-7's electrical packages/components. I've decided to not do it until I'm convinced otherwise...

You might consider adding grounding straps to the back of your car, too. I haven't, but that's because I'm willing to forgoe whatever the benefit is rather than sport attachments that I think look retarded. I don't have tassels on my coat and I'll be damned if I'll have any on my rotary rocket.

Make sure that all your connections are clean. Scrape away paint and remove any dirt or oil. Use an external tooth washer between each connector and the surface, if you can. And tighten the hell out of it. Use a spray-on enamel or good-sized dollop of di-electric grease on all the ground points to inihibit corrosion (if they start to rust they won't be as effective - my boost-sensor ground started to corrode not long after I put it in - I first noticed it when the stubmle started re-appearing! I cleaned it up and nailed it with di-electric grease and she's been fine ever since.)

Howz that for flame-free? ;D

ttyl,
Amur_

91vert

Wow....thanks for the detailed reply!

I am going to get busy on it today maybe.....but I don't think I'll go as crazy as you did.

On the air boost sensor (which I'm guessing is the Atmospheric Pressure Sensor in the Mazda Service manual) I'm assuming you ran a ground from the sensor connector to the chassis. If so, what terminal is ground? It looks like the manual lists both a Boost Sensor and an Atmospheric Pressure Sensor. From the pics in the manual they look to be the same thing. Is it a boost sensor on a turbo and Atmospheric Pressure Sensor on an n/a?

I know that one of them is probably a ground that goes back to the ECU, but I don't know which wire it is.

Thanks!

Amur_

It turns out that the colour of the wire from the boost sensor varies with the car's year.

https://www.rx7club.com/forum/showth...threadid=34026

This is a thread I started asking which wire to ground... The colour difference is identified 3 posts down from the top. And you might want to check out the rest of it.

You're looking for the Boost Sensor. It's right smack behind the air cleaner. The APS is elsewhere.
The turbo diagrams just identify a 'Pressure Sensor...' I'm not familiar with the differences between turbo and NA.

You're welcome for the detail. I prefer it when instructions are clear as vodka, myself (while saving the vodka 'til she's off the hoist.) ;D This is why I hate the Haynes manual. Unless all you need to do is change a light bulb, you might as well keep your Haynes in the bathroom for when you run out of Charmin'.

ttyl,
Amur_

SpeedyRotary

Are the ground wires the same as on an turbo 10th AE?

Amur_

With the exception of the boost sensor wire (check the link to make sure) all of the ground locations listed are suitable for all FCs.

dr0x

Just for the extra reassurance earlier today I threw 3 new grounds on the car. One from just left of the front spark plugs, where normally the ac bracket mounts, one on the flywheel cover under the UIM (kind of close to the factory ground) and one from the water pump housing to the strut tower. Once I relocate my battery to in the car Im going to be running 1 from the exhaust to the battery, one from the battery to the chassis and from the factory battery ground to the new battery (also grounding that onto the chassis). Probably a bit over kill, but oh well. Not like its expensive