280Z rough idle, can't WOT else it dies, heistation on acceleration

[iDev]

HybridZ members,

 

I have a 1976 Datsun 280Z with a L28E. I've been having quite a few problems lately that maybe can be addressed since I've been running in circles. To start off, when I start the car it has a quite rough idle and high idle, like around the neighborhood of 1-1.5K but sometime goes to 800RPM's but is really rough and shakes the car quite a lot and it sounds like its missing on some cylinder during idle, constant popping from the exhaust. If I give it some gas, I can hear this sort of sucking/hissing sound by my air filter and the engine bogs down but starts to gain RPM rough as well like its also misfiring on cylinders as well. I thought it was the PCV hose because it had a hole in it so I replaced it but its still makes the noise, still a vacuum leak somewhere I believe. If I give it full throttle, it will just bog down to the point where it will die if I don't get off the gas. I did some checks in the EFI bible and that everything checks out except the fuel pump relay seemed to not have and continuity and that the air regulator didn't continuity as well. I already replaced the fuel pump and filter and checked all the connections though I still need to give them a cleaning.

 

If the fuel pump relay was bad, wouldn't it not start the fuel pump at all? What will a bad air regulator cause? What other things can make the Z run poorly besides the FI components.

 

Also my AFM was missing the ground cable to it when I got the car, I since found another one but could a missing ground cause these problems as well?

 

I'm pretty new here so I'm still getting the hang of things, sorry if I come off as ignorant or dim witted.  

Edited April 29, 2013 by iDev

[NewZed]

When was the last time that it ran well?  

 

"I did some checks in the EFI bible and that everything checks out" means that only some things checked out, and there are things that you didn't check.  Best to check everything.  I would use the 1976 FSM, Engine Fuel chapter, in addition to the "bible".

[iDev]

It's been about maybe 1-2 years since it was last running well?

[Interrobang]

Sounds exactly like how my '77 was misbehaving. Turned out to be the water temperature sensor (or at least replacing that fixed it). Cost $15, got it from Amazon.com, believe it or not.

 

Off the top of my head, I remember that L-Jetronic senses Air flow, air temp, water temp, and ignition pulse. Air temp and air flow readings come from the AFM, water temp sensor is in the themostat housing, and ignition pulse is read off of the coil (or maybe the distributor, I don't remember).

 

If you have verified that you have good fuel pressure as well as spark on all cylinders, start checking your sensors. AFM/air temp is the expensive one, but you might find a used example in the classifieds here.

[Pharaohabq]

Might also check your Distrib is bolted down and set properly.  Ignition timing should be 10 deg before TDC if I remember correctly off the top of my head. It's in the FSM. If your ignition timing is off it could act like you're describing. There's a lot of things that could cause issue.  Maybe pull your plugs and clean/gap them, then inspect your plug wires, cracks and such could also cause issue. Lastly it's possible the Cold Start injector could be stuck and pushing too much fuel in causing a too rich condition. (that's why his water temp/thermotyme was important)    Anyway all of those parts listed above can cause issue too, but use the FSM to test before replacing or you could throw away $...

Edited April 29, 2013 by Pharaohabq

[iDev]

Thanks for all the responses guys! Appreciate the advice/tips. 

 

I don't think my water temperature sensor is bad, it was within in spec of ohms of the water temperature of the engine. Still need to clean the connectors though. Is a good cleaning solution such as deoxit good?

 

I pulled my plugs and they have this really sooty/black carbon deposited texture on them. For some reason the plugs inside were Autolite instead of NGK so I need to get some new plugs. Would NGK BKR7E 0.9 gap be good? I run them in my 2004 Nissan Pathfinder. Could the car be running rich? On the distributor, is the marking on the side of it? 

 

Also this is a bit off topic but is there a specific coolant that goes in the coolant overflow bottle? I just put some 50/50 Prestone antifreeze/coolant that my mom had for her Cadillac.   

Edited April 29, 2013 by iDev

[Pharaohabq]

Black soot is very often an indication of running too rich. That would also add to my theory of the Cold start injector being turned on.  The Thermotyme issue often causes hard starting and rich running due to a failed thermotyme or water temp sensor.  If you really thing the water temp sensor is good, then test the Thermotyme.   autolight plugs are fine. You're not going racing everyweekend yet so just cleaning those and resetting the gap should be fine.

 

The distrib has a bolt holding it down. there's notches,  If it's tight still then don't mess with it, it's probably fine.  If it's loose then you might set it to the center then tighten it down. You'd then have to set the ign timing properly in that case.  I assume you've D/L'd the FSM and EFI manual.  look up the Thermotyme faults in there.

[ISPKI]

As others have stated, the EFI system in these vehicles is extremely delicate. Literally any tiny issue could cause the symptoms you are experiencing - bad ground, vacuum leak, clogged fuel line, corroded connectors, missing clips on your connectors. Take a look at the tiny vacuum line feeding into the fuel pressure regulator - mine was slightly torn when I got my car, not enough that you could hear the vacuum, but enough that it was not letting the regulator operate properly. Also - check for fuel pressure by tapping into the fuel line with a gauge between the filter and rail. If your connectors are badly corroded or your connectors are missing their locking clips (most of mine were missing) I would contact FricFrac on this forum about his replacement connectors for the L28E - very worthwhile investment IMHO.