GenHawk

Hi - I have a 1980 non-turbo with California emissions - the problem is it runs like crap when it's cold. Once it's warm (1-2 minutes) it runs great but with some hesitation in the lower power band (up to 3000 rpm), over 3000 it is super. I had it in the shop and replaced the entire exhaust (made it run better since the exhaust was bad before, but it didn't help the cold start). The cold start valve tests good, emissions are good (although I get a little white smoke on startup). Mechanic played with it for several days but wasn't able to figure it out completely - he thinks it might be the AFM.

Any suggestions or ways I can test that? It's an expensive part and a CA model might be hard to find. Anything else I can look at?

Thanks, Gen

Bleach

Does it idle low when cold (less than 800rpm) or does it just lack power and misfire... rough idle?

Could be tiny air leak on intake causing it to run slightly more lean. The mixture is set to run slightly rich when cold and any minor change in that can effect the cold running. If it idles low, not at 1100-1200rpm, then the fast idle "relay" could be bad. Those go out often. Its that device on top of the intake manifold near the throttle body.

Cold start issues are common problems for the 280zx. Mine has a simular problem. Part of the problem was my distributor. The vaccume advance was gritty and stuck. So the ignition timing was slightly off at lower rpms (high vaccume) After replacing the distributor, my car has better cold starts (not perfect) and much more low end power, especially when cold.

GenHawk

Thanks for the info - it idles rough, not low. Is that relay expensive?

Bleach

If it idles high but rough, then its not that relay thing. Its more of a valve I guess. I'm sure its $50 or more from Nissan to buy one new.

Maybe your problem is timing or ignition. Have you done any tune-up work recently?
Also, try advancing your ignition by losening the little bolt at the base of the distributor. Turn the distributor a little clockwise (I think). See if that changes the smoothness of the idle. If so, your vaccume advance is probably not working right.

I would think it is probably not the AFM.

duckyz

Here's a simple fix...Well, it helped mine anyway.

Disconnect the battery and remove the ECU. Clean off all the contacts with an emory board, put some di-electric grease on the contacts, and button everything back up.

I know, it sounds stupid, but a little corrosion on those contacts makes a HUGE difference in the way the car starts and runs.

The first start up after cleaning may be a little rough, but after that it should get better.

newb81280zx

My car has a similar problem it sounds like. I made a list of what all I plan on doing/checking this weekend maybe it will help you out. Clean ECU terminal, replace dist. cap and rotor, check timing, check plugs/ replace, change fuel filter, clean AFM, check cold start valve, Check vacuume lines, change air filter. IDK i'm lost too but i'll let you know if anything works. Good Luck.

GenHawk

Sorry it's been a while. Thought that someone might be interested to know that the problem was traced to bad electrical connections on the throttle position sensor. Car runs really nicely now. =)

Gen