Hesitation during acceleration

[DC871F]

Thanks for all the help guys.

It seems the vacuum advance is shot. Been looking around for just the advance can, but no dice. Can get the entire distributor, but that seems overkill and expensive. 119,000 miles on the car, so the distributor should still be good. 

Anyone know where to get the correct part? The regular parts houses offer only rebuilt distributors, not the advance, or at least not the correct one.

[Zed Head]

Is it the vacuum can or the breaker plate?  They can both go bad.  How did you determine that "it" was bad, whatever it is?  The diaphragm in the can can spring a leak or the bearings in the breaker plate can fall out.  Both will stop the advance from working.

Beside that, your symptoms sound more like a running lean problem.  You could try the coolant sensor tweak while you're looking for distributor parts.  The problem is pretty common and I think that several 10 ohm resistors have been found in the wiring harnesses of various 280ZX's, if my internet memory serves me right.  Today's gas is not the same as 1980's gas.

[DC871F]

Spring plate operates smoothly and returns fine when exercised manually. The diaphragm definitely is not working, with a vacuum bleeder or sucking on the hose, just pulls air.

 

[Zed Head]

I might have a ZX vacuum can that's still intact.  I'll dig around.  

You'll still need a new canister, but I wonder if the hesitation was from the vacuum leak.  You might get by in the mean-time by just plugging that hose.  Might be a bit "doggy" at part throttle with no advance, but better than hesitation.

[DC871F]

Yes, multi-faceted. It ran smooth once I got it back on the road, pulled real nice. After the hesitation started I then went through all the electrical connectors, then re-inspecting all the vacuum lines. So once I got (back) to the distributor is when I found the advance sucking air. Car sat for 20 years, so the condition of the diaphragm may have been poor.

I found the resistor on ZCar depot, probably not a bad idea.

Won't be near the car for about a week, so it will have to wait. I appreciate you looking for parts, thanks. It seems that the advance is going to hard to source, not sure why since a reman distributor is easy to find.

[rcb280z]

I would probably replace the advance canister before "tweaking" anything. Might solve your problem. Just my 2 cents.

[siteunseen]

I'm stuck inside today and read from one end of the web to another looking for a vacuum advance.  There's tons of info to read. 

I think I would start a new topic on repair or replacing the vacuum advance module.  I read a lot on the Australian Z car forums but now that Photobucket SUCKS @Captain Obvious I couldn't view or copy and paste any of the photos but there were a lot of threads on the diaphragm being bad and the fix, but I couldn't see it because Photobucket SUCKS.

Good luck, I'm going to bed, my eyes hurt. 

[Zed Head]

17 hours ago, DC871F said:

 Car sat for 20 years, so the condition of the diaphragm may have been poor.

I found the resistor on ZCar depot, probably not a bad idea.

Won't be near the car for about a week, so it will have to wait. I appreciate you looking for parts, thanks. It seems that the advance is going to hard to source, not sure why since a reman distributor is easy to find.

I took a leaking one apart in the past and the diaphragm material was cracked and brittle.  Made me wonder if they lost performance before they actually cracked and leaked.

zcardepot has a fuel tweaker?  Can you post a link?  I looked but didn't find it.

Might be a day or two before I refind my distributor parts.

[rcb280z]

2 hours ago, Zed Head said:

zcardepot has a fuel tweaker?

Variable Resistor for Fuel Injection Mod 280Z 280ZX

Part # : 800-958

$3.99

Here you go.

[Zed Head]

Thanks.  His site is down now so I can't check it out.  The "tweak" is well-established.  It's not really a tweak anymore, more actually a "fix".  

Not really feeling a bad vacuum advance as a hesitation problem, that's why I suggested the fix.  DC8 didn't say if he plugged the vacuum leak.  It would be a small one but still might have an effect, especially with the an engine on the edge of leanness.  The first thing that I would do is to plug the vacuum leak.

Edited December 28, 2017 by Zed Head

[madkaw]

Right- how about a small vacuum leak- lean , plus advance that doesn’t work that is supposed to help with lean conditions of cruise . 

Just dial in 18 or so initial and plug the vacuum advance until you find a diaphragm 

[Zed Head]

The vacuum advance goes away at any sizable throttle opening.  As soon as the the blade opens and intake vacuum drops the advance won't come back until engine RPM increase.  So part-throttle acceleration would see a difference but it goes away as you press the pedal farther.

All I'm saying is that my math doesn't add up to the lack of timing advance itself as the problem.  Maybe the mechanical advance is stuck also.  I don't see any timing light info.

I just went back through the whole thread and see the things I missed.  But, basically, it's an engine with a hesitation at some unknown level of acceleration, and a hole in the vacuum advance canister.  That's really all that we're working with.  A little work with a timing light would be illuminating.

I found the old ZX canister.  It's from an 81 2+2 so should have up to 15 degrees.  Looks like some sort of two-stage system.  Could also be an 80 unit (it had 1980 transmission).  Which has even more possibilities.  The 80's was the emissions era.