datsunl28et

Hey guys just wondering if you would know why my car idles very irregular. Idles very bumpy under 2000rpms? I was thinking maybe the disc in the distributor is flipped, or something. How would I tell if the disc is installed properly. The car has done this since the day I bought it thought it just needed a tune up and fresh gas. So far the car has recieved new wires plugs and all filters changed, fuel treatment, alternator and belts. Runs fine though above that RPM range. It has also developed an exhaust leak on the manifold, I noticed one of the bolts was missin the other day, this did not effect the cars idling problem though. Just was wonderin if anyone new the bolts size and thread? Thanx for any support and advice!!!


Nick

jfairladyz

could be a faulty idle control valve. it's located on top of the intake manfold and is controlled via its vacuum control module (which could also be faulty) which is near the AFM. That is controlled by the ECU (i wouldn't suspect the ECU). But either one of those two parts could cause your problem. Check first and foremost for a vacuum leak though.

NismoPick

Good call. The hose from the J-pipe to idle control T sometimes gets kinked & will cause idle probs if it is.

datsunl28et

Well I plugged alot of vacuum lines that were in my mind doing nothin. so no vacuum leaks that I know of. Idle control vavle is very possible, and it is throughing a sensor light as well so.... thanx for the suggestions.

jfairladyz

sensor light? The only sensor light should be the O2 sensor light.

nismo619

might be the dizzy set back "retarded " to much ? might want to get a timing light.. 500 rpm normal.. but i set mine at 800 rpm..

SpeciallySpiked

I'm pretty sure your idle should be way above 500
the 83 says it should be at 900

jfairladyz

500 is too low. Factory setting for a turbo is supposed to be around 7-800 rpm. I set mine a litte higher though, around 900.

RodMoyes

So I wonder just how many different "Crappy idle" threads there are in the 280ZX section by now?

It seems to be the single biggest issue among our crowd.

I learned how to fix mine finally... after three years of screwing around with it and replacing thousands of dollars worth of parts... you guys want to know the real sescret for solving the crappy idle problem?????


OK, but this may sting a little...















Drive your Civic instead





Everytime I drive a different car, my problem goes away!


Sorry, just venting.

The truth is... I don't think these cars EVER idled well to begin with.

I've just learned to live with it.

I can MAKE it idle strong, but at the expense of whacking the mixture out big time.

At $4.00 a gallon, I don't really want to burn extra fuel just so my car will idle smoother anymore.

Rod.

Bob79280zx

I will agree with Rod. You can do everything you can to these cars, and they will still idle funny. I just got done rebuilding most of mine, and you know, its still doesnt idle all the time at one set spot.

Just have to deal with it.

PooFlinginMonke

You would be amazed how cleaning the throttle body and all the ports will raise the idle back to stock specs but I believe something else is at hand here.

jfairladyz

My NA didn't idle to great either. Other than that it was strong as hell though. The turbo idles like a dream though. Nice and smooth. Sucka's

SHADY280

i got a brand new 60mm tb, and it idles crappy too, well maybe thats the race cam?

datsunl28et

Ya it will idle it just bounces back and forth from below 500 to about 900 in gear (automatic, AKA slush box) and hesitates alot til about 2500RPMs or so then it runs super smooth. The O2 sensor is brand new but the sensor light is still on and it kinda misses sometimes too. It has new pluggs wires and distributor by the guy that sold it to me, and I have changed the pluggs sense then, so Im kinda at a lost here. And does anyone know the exhaust manifold bolt size and thread?

jfairladyz

Sounds like maybe you've got an injector or two not firing. This problem is most pronounced in the lower RPM's and aside from a lack of overall power, isn't noticable in upper rev range. Could be bad injectors, clogged injectors, or most likely then either of those, a bad connection at the injectors. Check for corrosion at the connectors or loose wiring going in.

The sensor light is meant to be unplugged. Once it comes on, it's not meant to ever be used again.

datsunl28et

Well I will check out the injectors then that sounds like agood idea. some times the car idles perfect but thats like every few days and only for a short period of time when it does. maybe I should just go ahead and replace all of the injectors as well. I just chabged the fuel filter too, but no noticable difference. The car sat for a year and a half, started here and there in that time but had a full tank of gas the whole time and it really ran like crap then, but definetly a big improvement since then with new gas and fluids changed and all filters ,just striving for perfection, cause I really want it to turn out nice and not go down hill when Im done with it.

lww

All of my Z's idled fine and smooth in stock form. It's only when I started messing with them that they started to get finnicky.

800 to 900 rpm is the stock idle setting. 500 rpm is WAY too low.

My 240Z idles at 900 rpm perfectly. My 280ZXT idled fine and at about 800 rpm until I pulled the motor out of the car...

A smooth idle is important because it indicates how smooth the engine is running at all rpm's when the higher speeds may mask a problem.

If you have an injector that's not flowing very well, you can get a lean condition in that cylinder at higher rpms that could cause detonation and pit the top of your piston leading to more significant problems in the future.

Check your ignition system first. If it really is only a problem at idle, it could be spark related. Gently remove the ignition module from the distributor and clean both the back of the IM and the mount on the distributor. This is the ground for the IM and any bad contact will affect your ignition.

As mentioned, corrosion at the injector connectors is the most common problem followed by corrosion on the electrical connectors for the various sensors, corrosion on the ECU connector and finally, just old worn out injectors.

TPS and AFM would be the next area I would check.

Rod can probably give you a whole litany of what to check and possibly replace.