How many important grounds are there and where are they?

[90 GSX]

My car won't idle constant... It seems like it just idles wherever it wants to at the time, paying no mind to the fact that I set the idle at around 750-800 and the IPS works fine. There is no suring or anything, and it is very manageable, but the the rpms do not stay up when I'm coming to a stop, it always just idles wherever it wants. I also have some seemingly random fluctuations in my fuel trims. I thought that a bad ground could cause something like that. Where are the grounds located? I know that there is one from the exhaust to the body, and two from the tranny to the body right?

 

[1stGenRocks]

not sure why but on my car the throttle body wasnt getting a good ground. i just added a ground wire straight to the TB. if you have a datalogger check and see if your idle switch/closed throttle switch is working.

You can also check whether the tb has a good ground by measuring resitance from ground to the TB or volts from the positive battery terminal or a bunch of other ways depending what tools you have on hand.

as fasr as i know the only stock grounds are from the battery terminal one wires to the firewall and one wire to the bellhousing bolt for the trans. the headlight harnesses also have little screw on grounds by the lights. the exhaust ground doesnt do much.

 

[steve]

The two main ground were mentioned. The wire gtom the negative battery to the firewall and the wire to the bellhousing. Also mentioned was the throttle ground strap than runs from one of the TB studs to a screw on the top of the TB. Not mentioned is the ground for the intake manifold from one of the two bolts holding the throtte cable to the firewall.

Running a ground from the negative terminal to the alternator case or bracket is a good idea.

Have you measureed the ISC coils and checked that it's working correctly?

Steve

 

[90 GSX]

Thanks for the responses.

I have checked the ISC (I actually have 3 working 1990 ISC's) and it works perfectly. In fact, I have no problem with using any accessories at idle.

I checked the IPS by putting my multimeter in series between the connector and the terminal on the IPS and it opens the closes the circuit fine.

I have not heard or seen a ground on my throttle body EVER. Is this bad? There is a little screw on top of the TB and I never figured out what it did, I just passed it off for a useless bracket or something. Where is this TB ground supposed to be exactly???? Keep in mind I have a 1990 throttle body... I'd like to do this ASAP.

As for the intake manifold ground, there is a wire going from the firewall to the bolt hole on the back of the intake man. where that big wire loom bracket bolts down. I did not think that it went to the throttle cable bracket screws... should I move it or does it matter? They are both connected to the intake.

How should I test the continuity from the TB and the intake manifold? Should I just ground them to the body and check the resistance to see if its low enough???