83 ZX Chugs. Suggestions?

[83 Toy]

Just picked up an '83 ZX turbo 2+2 at a yard sale.  Body/interior are beautiful.  Engine clean.  However, the idle is rough and it chugs at low RPM and very poor acceleration.  Nissan installed a new fuel pressure regulator but now it runs worse!  Any suggestions what to do next? Any advice is very welcome.

[JSM]

Start with the plugs.  Are they new, if not, condition? Does it smell like it's getting too much gas?  Could be a multitude of things.

Also gremlins in wiring are not common in the ZX.  The one I had would run horrid all of a sudden and the fix was I took my foot and pressed on the ECU connectors.  The kick panel for the ECU is drivers side right by your left foot.

Edited April 27, 2017 by JSM

[Zed Head]

2 hours ago, 83 Toy said:

Just picked up an '83 ZX turbo 2+2 at a yard sale.

 Nissan installed a new fuel pressure regulator but now it runs worse!

A yard sale?  What kind of yards do you live by?

So a Nissan deanship diagnosed it, replaced the FPR, and it runs worse?  Doesn't sound like much of a dealership.  Did they tell you anything before they did the work?  

If you had a dealer replace the FPR then, unfortunately, an 83 Turbo might be difficult for you.  It's not the best car to learn on.

[83 Toy]

Yeah, we just got lucky with the car.  I've never seen anything like that at a yard sale! I could have easily replaced the FPR myself but I had already paid $$ upfront for a diagnosis. They applied the money for diagnosis towards installing the FPR.  The cost was a wash and I don't have a pressure gauge for diagnosing.  The pressure was around 20 and 38 is recommended. So, theoretically, the fuel pressure was too low but the car ran better than it does now.  Not sure why.

 

[83 Toy]

Thanks for the advice re replacing plugs and checking ECU.  I'll give the ECU a swift kick and let you know and let you know what happens

.

[Zed Head]

Could be a PO "tuned" the engine around the low fuel pressure.  Now that you have it corrected, the "tuning" might need to be undone.  

There are many small things that need to be right for the engine to run right.  You have a long path ahead of you, especially with a turbo engine.  a turbo engine running lean due to low fuel pressure could easily suffer detonation and break some ring lands or damage a piston.  You should really start with the basics and measure cylinder pressure, valve lash, timing, etc. to be sure that they are correct.  Unknown engines can be full of small problems and mis-adjustments.

Check your cylinder head temperature sensor resistance, and connection, maybe you'll get lucky and find that it's disconnected or broken.  That would cause rich running.

Edited April 28, 2017 by Zed Head
brake break

[Patcon]

Also check any of the rubber boots at the intake for leaks. Major vacuum leaks and the low fuel pressure will make the idle very weak...

[esmit208]

I see the car has California plates on it. If you are nearby the Los Angeles area call or go by ZXPERTS in Venice on Lincoln Avenue. Richard Keebler is the owner and they can straighten it out for you. It is probably NOT a single issue and they will know what to look for..

[83 Toy]

Thank you all for the advice.  A friend recently told about Mike's Z Shop in Whittier.  We were thinking about taking the car there.  Do you know which place is better?