L28e sounds like it's starving for fuel after sitting for 30mins or more...

[kastmaster]

Hey guys, I've been trying for the last 2 weeks to trouble shoot this problem, to no avail, and I wanted to see if any of you wise men (and women) could put in your thoughts before I go and starting buying little specialty diagnostic tools.

 

PROBLEM:

-Car ran fine, zero problems a month ago. But was running WAY too rich for smog test. Air Flow Meter was the problem, shop had it replaced and passed smog test with flying colors Ever since that AFM swap, car starts/idles like crap for the first few mins ONLY if it sits for more than 30 mins. Upon initial start up, it usually cranks the first time but does not fire. Second time cranking fires up but ACTS like it wants to die due to not enough fuel (or too much air?)

 

THINGS REPLACED SO FAR TO ATTEMPT TO SOLVE PROBLEM:

-New Fuel Pressure Regulator

-Swapped brittle vaccuum hose going from FPR to the intake manifold.

-New Oxygen sensor

-New Fuel Filter

-New plugs (genuine nissan NGK)

-New Distributor cap, and rotor

 

POSSIBILITES I AM THINKING OF FOR PROBLEM

-Possibly a vac leak? Maybe around common spots for Zs like Orings, intake manifold gasket, etc? I read a little trick to detect vac leaks, is to blow a gentle stream of propane around suspected areas of leak, and see if the car "evens out the idle"? Hmmm.

-I also thought, possibly a faulty Cold Start valve? Maybe plugged with small debris or something.

-I'm also going to try pulling the air regulator (does that sound like a worthy culprit?) and do some visual checking as per the Haynes manual visual inspections. Maybe it's stuck closed? (Since I have to MANUALLY open the throttle plate with my pedal to alow more fuel delivery to the injectors.

 

Let me know if I'm taking non-sense haha

 

Any thoughts? I have to push the accelerator pedal down about half an inch to keep it revved around 1200 rpm, just so it doesn't die on me, and THEN I can feel a change in engine rev after 30 secs of doing this. It's like something is warming up? I'll do my best to post a video of the problem, because I'm sure visuals are more helpful than just words. Thanks a bunch you guys, your help is much appreciated.

 

EDIT: A few more things I've thought of. The new plugs are OEM NGK BPR6ES I have them gapped at 1.0mm (0.039") (As per the Haynes manual specs) Should I perhaps try bringing them down to 0.035"? I was doing a lot of reading in the archives about what plug gaps most of you guys are doing. I mean, there is no missing through the RPM band when accelerating, just missing and chugging upon intial cranking and firing. Just thought I'd throw that in there

[smoorenc]

Check for rust particles in the little cone filter at the inlet of the fuel pump. You;ll have to take the incoming fuel line off to see it.

[Pop N Wood]

Take it back to the shop that put in the AFM and tell them to fix their work.

[kastmaster]

Check for rust particles in the little cone filter at the inlet of the fuel pump. You;ll have to take the incoming fuel line off to see it.

 

Thank you for the input, my gut has been telling me that there is some kind of flow restriction possible, thus not getting enough fuel pressure.

 

I did some other test to help narrow stuff down. I pinched a fuel hose, right before it connects to the metal fuel rail itself, but after the fuel filter, and the idling did smooth out considerably (not perfect, but I was surprised anyway) since the pinching of the hose with a wide needle nose plier caused the engine to go from the usual initial startup lumpy idle at 500-550rpm, to a more steady and (audibly) stronger 700-800rpm. Doesn't the pinching of the fuel hose line create more pressure in the line? (I just tried this by pure curiosity)

[kastmaster]

Thanks again for your valuable input!!

 

I finally had a free weekend (busy with school) to pull the Air Regulator off my 280zx after it sat through the whole night, and I looked through the air hole to find that it was almost completely closed (about 1/8" of a gap was opened)

 

I then stuck the Air Regulator in the freezer, let it sit in there for 20-30 mins, and took it back out, and the gap hardly even changed! It was neither completely open NOR completely closed both before and after the freezer test!

 

I have come to the assumption that the inner spring inside is possibly worn out? Let me know if anyone agrees. Time to replace the Air Regulator?

 

NOTE: I did spray the inside with Carb Cleaner to free up any gunk that may have been restricting movement of the spring inside Air Regulator BEFORE i did the freezer test, but it did not help any. Dead Air regulator would justify my wacky stumbling at idle during initial warmup wouldn't it?

 

Have a great weekend all.

[COZY Z COLE]

Have a read of the main. & trbshooting section...http://www.atlanticz.ca/zclub/techtips/EFI&fuel.htm

 

 

LARRY

[kastmaster]

Have a read of the main. & trbshooting section...http://www.atlanticz.ca/zclub/techtips/EFI&fuel.htm

 

 

LARRY

 

Larry, thank you for that link! I check up on the link titled "AAR" and it seemed to confirm the problem I was having. If any luck with the new part installed, I'll be sure to update back for others having same problem. Thanks again Larry, that was a helpful read!