240Z, 260Z, 280Z Performance / Technical Discussions related to performance motor enhancements, upgrades.

77 280Z running poor

Old 03-06-2012, 09:28 AM
  #1  
Registered User
Thread Starter
 
Join Date: Jun 2010
Posts: 5
77 280Z running poor

All, looking for some recommendations. My son-in-law picked up this car and it was in real need of work. Turns out the intake and exhaust bolts were only finger tight and the gasket was blown bad. We pulled the head only to find out it was cracked in the 3 & 4 exhaust ports (N47). Got a new used head, got it all cleaned up and put on with out to much issue.

It's still not running good. Vacuum is holding at about 5psi at idle and the fuel pressure is at 32psi pretty steady. As you might guess, it's running really rough, smoking quite a bit and stalls when you hit the gas. Once it warms up, it won't start again till it cools off.

So, for starters, it's my understanding that the vacuum should be about 20psi. I've looked all over, shot carb cleaner but I'm not finding a leak. We have yet to do a final set on the valves and I'm wondering (actually kind of sure) if that could cause the low vacuum. Secondly, I know 32psi on the fuel is a little low, replace the fuel pump too or should that be OK?

Anything else I should look at? One more thing, the hose that runs from the block to the bottom of the exhaust was burnt bad. We taped the hell out of it for now till we can find a new one. Could that be making the vacuum this poor as well?

Thanks,

Delorian
delori is offline  
Old 03-06-2012, 09:37 AM
  #2  
Registered User
Thread Starter
 
Join Date: Jun 2010
Posts: 5
Sorry, that hose from the block connects to the bottom of the intake. Also, after the car is turned off, the fuel pressure drops off to about 20-25psi after about 15min. Is that OK?

Thanks,
delori is offline  
Old 03-06-2012, 11:18 AM
  #3  
Registered User
 
Join Date: Jul 2011
Posts: 68
Bad Idle could be caused by a bad/poorly set TPS, and the ignition coil. Playing with the A/F screw on the AFM too might help as well.
Bates is offline  
Old 03-06-2012, 12:01 PM
  #4  
Registered User
Thread Starter
 
Join Date: Jun 2010
Posts: 5
I'll check the TPS first as we swapped in a spare AFM and it didn't help.

Got the valves set, now need to pick up a new valve cover gasket and we are checking on a new PCV hose. See how it runs after we get these.

Thanks,
delori is offline  
Old 03-06-2012, 02:11 PM
  #5  
Registered User
Thread Starter
 
Join Date: Jun 2010
Posts: 5
OK, gotta order a PCV hose online, parts stores don't have one.

TPS was not reading zero, adjusted and is now good, Thanks for the tip

Valve adjustment didn't help vacuum, still only 5 PSI. Give it gas, drops to zero, let off the gas, goes up to 20 and right back to 5.

The screw on the AFM was turned all the way in. Backing it out a bit did help bring the idle up some, but it's still extremely rich, but it will run (at idle) a lot longer now. Once it dies, it still will not restart so I can't even drive it to the shop like this. (Z-Garage in San Jose)

Exhaust is still black, blowing fluid, and after the fluid dries up, there is a big patch of carbon... Plugs confirm...

Anything else you can think for me to try? Timing is set at about 11 BTDC now and spark is nice and blue. I did set the air gap in the dizzy, it was really wide prior. I wish I knew why the vacuum was so low or is 5 normal...

Thanks,
delori is offline  
Old 03-07-2012, 07:04 AM
  #6  
Registered User
 
Join Date: Jul 2011
Posts: 68
Try a different coil. I will bet it will make a world of difference. My 78 ran like crap until I swapped out the ignition coil.
Bates is offline  
Old 03-17-2012, 04:50 PM
  #7  
Registered User
Thread Starter
 
Join Date: Jun 2010
Posts: 5
Dear Mr. Bates,

Well, it took a while to get my daughter that has a running Z and her boyfriend together with a bit a time to play. We pulled the MSD coil from my daughters car and dropped it in his, VIOLA!!! Runs like a champ! Thanks for the tip! They are out picking up one for his car with his car and her coil right now.

Thanks again!

Delorian
delori is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Mhinrichs
The Lounge (Off Topic)
4
12-05-2007 06:35 PM
RedStage
FS: 240Z,260Z,280Z & 280ZX (70-83)
3
07-18-2005 04:22 PM
AVCM
240Z, 260Z, 280Z (S30) Forums
7
01-20-2005 10:40 AM
RedStage
FS: 240Z,260Z,280Z & 280ZX (70-83)
0
10-09-2004 10:45 PM
RedStage
FS: 240Z,260Z,280Z & 280ZX (70-83)
0
08-26-2004 11:31 PM


Thread Tools
Search this Thread
Quick Reply: 77 280Z running poor


Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.