Hesitation during acceleration

[siteunseen]

I bought my first 280 for $1,000 back in the late 80s.  It would crank and idle but nothing else.  Guy was frustrated with it and took my offer, all the money I had at 18 years old.  He also was married with children and couldn't drive the foreign car to his job at the steel plant.  They would cut the tires back then, Buy American was the war cry around here.

Loaded it on a trailer and tracked down a local legend, "The 280 Lady".  She had it running in 30 minutes. 15 of that was checking the basic stuff then the TVS then popped the cover off the AFM and tapped the weight, it was stuck.  Got in and beat the hell out of it around the block.  I gave her $25 bucks.  

Good Karmal is what my Dad says.

Pay it forward! 

 

[siteunseen]

http://www.classiczcars.com/forums/topic/59224-hesitation-during-acceleration/?do=findComment&comment=539001

[DC871F]

1 hour ago, Zed Head said:

This is the most descriptive description so far.  Stuff to ponder.  Nothing comes to mind.  An alternative ,or complementary (practicing my words), description might be that it "bogs" in 3rd gear at a certain RPM, if the gas pedal is held to the floor, but picks up again if the pedal is released a bit.  It feels familiar, back from my carb'ed car days.  

When you release the pedal, you're throttling the air flow.  Maybe making it match a stuck AFM vane.  That just came to mind.  The AFM vanes have been known to get stuck.  They're delicate, meant to respond only to air.  A stuck vane would cut air flow slightly, but reduce fuel enrichment, a lot.  The air would slide by, but the ECU would only see vane position.  You might check that.

I took AFM off the car, inspected under the cover, clean as a whistle. I also looked at the vane movement, felt nice and smooth, no hangups, not dirty inside the airflow side.

It bogs in all gears, I was just giving an example. Deficiencies in communicating in this manner definitely rears its ugly head doesn't it? 

In 5th gear doing 65 MPH, you can stab the gas peddle to the floor, and notice the car being "held back", but if you do the aforementioned "throttling" of the gas peddle, sure enough you'll find the sweet spot and its off to the races.

I really hate to go back through the fuel injection, but maybe theres something up there. But I dont want to muddy the watter quite yet.

[Zed Head]

For the 280Z's the TVS is supposed to send the signal to the ECU to add an extra 27% of fuel over the base.  Maybe it's not the TVS thats' the problem but the circuit in the ECU that uses it.  Maybe you have a bad ECU.  I can't find the percentage of fuel for 1982, so copied 1976 to show it.

This is from 1982 - 

This is from 1976 - 

[DC871F]

17 minutes ago, Zed Head said:

For the 280Z's the TVS is supposed to send the signal to the ECU to add an extra 27% of fuel over the base.  Maybe it's not the TVS thats' the problem but the circuit in the ECU that uses it.  Maybe you have a bad ECU.  I can't find the percentage of fuel for 1982, so copied 1976 to show it.

This is from 1982 - 

This is from 1976 - 

Hmm. Will a test unit determine a bad ECU, OB codes? I have talked to a couple different diagnostic shops, and they say its almost impossible to extract "relevant" information from a test unit for this vintage.

I'm pretty sure the TVS is good. I have a new distributor on the way since I need a new VA can, plus maybe a little troubleshooting with a new ignition module. I really hate throwing part at problems, but it does serve a little purpose just to get the vacuum system back in shape.

I was reading on a thread back a couple years ago, that someone had a cylinder dropping off, and after a bunch of troubleshooting, a new ignition module cured the problem. I admit, I am more of a venturi and float kind of guy, so at this point, I am doing OJT on this engine, but after reading that thread, I feel a little compelled to go ahead and invest a distributor and module. I do feel its dropping a cylinder, which make no sense, but I have been through most things twice at this point. 

ECU? Maybe a diagnostic code search is in order. Is that worth my time or should that be under the category of remove and replace?

[Zed Head]

No codes, even in 1982.  In the FSM troubleshooting charts the last item, if you can't find any other cause, is often "replace ECU".  Hard to say.

Somebody might have an inexpensive used ECU.  Borini63 sells a lot of 280ZX parts.

@borini63

Does you new distributor come with a module?  You can wire up a GM HEI module if not, for about $25.

[siteunseen]

I was just running my mouth. 

I think it's in the ignition somehow or another.

[DC871F]

10 hours ago, Zed Head said:

No codes, even in 1982.  In the FSM troubleshooting charts the last item, if you can't find any other cause, is often "replace ECU".  Hard to say.

Somebody might have an inexpensive used ECU.  Borini63 sells a lot of 280ZX parts.

@borini63

Does you new distributor come with a module?  You can wire up a GM HEI module if not, for about $25.

Comes with new module, but I'm waiting on the third one to arrive from O,Riellys. First one they sent to the store for me to pick up was a core, no joke, even said core on the box, complete with used dirt and oil. Second one they sent me, the module was broken, cracked, and fixed with RTV, so the checks in the mail.....

[rcb280z]

Just in case a "3rd" try doesn't work, Rockauto has them. And I guess there is a difference between the 79-80 and 81-83 n/a model distributor so beware. Not sure what the diff is but......

A-1 CARDONE 31619 {#D6K8003, D6K803, D6K822, D6K826, D6K901, D6K908, D6K909, D6K914} Reman. Distributor (Electronic) (Sweepstakes Entry!) Info		$88.99	$20.00	$108.99
		A

 

A-1 CARDONE 311002 {#22100P9100, 22100W3100, 22100W4800, 22100W4801, D6K8101, D6K811, D6K8202, D6K901} Reman. Distributor (Electronic) (Sweepstakes Entry!) Info

$144.79

$25.00

$169.79

 

Hope this helps.

[siteunseen]

The early ones have the one connection on the module, the later has two connection.  E12-80, early.  E12-92 later.  According to the spread sheet he needs the D6K81-01, which would be the two E12-92 I believe.

E12-92

E12-80

The spread sheet,

 

[JSM]

1 hour ago, DC871F said:

Comes with new module, but I'm waiting on the third one to arrive from O,Riellys. First one they sent to the store for me to pick up was a core, no joke, even said core on the box, complete with used dirt and oil. Second one they sent me, the module was broken, cracked, and fixed with RTV, so the checks in the mail.....

Do you need just the module?  I know I have an extra E12-80.  Not sure if I tossed the later E12-92.  You can borrow them if I can find the later E12-92.

[rcb280z]

He needs the later one. 12-92.

I have that graph also, just forgot I did.