L28et Z31 EFI suddenly running poorly (LONG)

[rayaapp2]

I know its usually bad when I need help, but often when I need help its some small minor detail that's obvious staring me right in my face that just cannot seem to see.

This will be long!

My S130 is running a L28et with a Z31 EFI system(1984 T) installed on an 82 harness).

I have a 5 knob apexi SAFC installed.

The z31 efi was on this car and running for ~20k miles without issue. 

Ive been hunting down problem after problem for the past few weeks. I am having the hardest time with this thing.
Mechanically the engine is sound. Its a fresh setup and Ive confirmed integrity(pretty much every other day at this rate). With the new engine, the Following changes were made

1. I add about 40% E85 to the tank(E85 being min 70% at the pumps). The rubber lines have all been changed and I dont let the car sit.
2. A large intercooler was added with associated piping
3. I installed a APEXi 5 knob analog Super Air Flow Converter
4. I went from a stock F54 bottom to a NA F54 bottom end(so Im running flat top pistons set loose)

 

I purchased a set of flow rated 310cc(stock) injectors and drove them around for 30k miles. One went out and thats when all of this started.

It turned out at this point, that something wasnt right still. I replaced the #5 that went off for warranty with one from my stash of other injectors of iffy conditions. The next day the engine during cruise felt un-even. I had a listen and sure enough #4 and #2 injectors had soft hits, letting me know they were flowing but likely low flow.

I finally found a set of injectors in like 5 dozen sets that I have around that were good enough for use and installed them. Meanwhile I dropped all my old injectors off for warranty and I am still awaiting them to be returned currently. I spent a number of days also dealing with IC piping blowing off! I finally broke down and replaced the offending clamps with T clamps. I made sure boost leaks were NOT an issue! lol

It drove fine for a day at this point. Now from this point on the car always idles 800-1000rpms perfect no matter how crappy the engine runs above that! No idle misfires, in fact it runs extremely well at idle for an L series.

Maybe 2 days of good driving goes by.

Then without warning it started running poorly again one morning. It runs like all cyl are leaning out bad. Again idles perfect! But it coughs and runs like dog poop above idle. At this point I discover the fuel filter that has about 10k miles on it took a giant crap! The filter element dislodged from the housing at some point. Being frustrated with premature failure of the filter and knowing what I then had to do I went at it. All the injectors came off, and I had to back flush them all to dislodge any crap that made it through/dislodged from the filter. I actually got a LOT of crap out. 

 

 

 

This is what came out of all 6 injectors after back flushing them.

 

 

This is what was left inside the filter and the filter itself that failed.

 

 

I replaced the filter with a WIX unit that night, and replaced that with a OE Nissan filter the next day. However little improvement was made. The car still did not run perfect. It was only marginally better than the day before.

During that day I decided to check the rest of the entire fuel system... again.
Fuel Pressure checked 38/51psi which is spec idle/boost wot
I removed the fuel pump and checked the screen on the inlet and it was clean. At this point I am baffled so I check everything starting with basics. Spark and Fuel time. 
Turns out I lost a ground at my ignitor, I was entertained by this one. My RPM gauge, didnt show an issue, but the APEXi SAFC 5knob has a cool feature. It lights up green, but each knob turns red as the rpm range passes through the knobs adjustment range. Well at about 4k+ rpms the knobs would light red like a blinking chrismas tree... randomized. That was how I tracked down the ignition issue. So I grounded the ignitor to the intake manifold where the EFI grounds as well. It drove well at this point! infact it pulled well into the upper RPMS.

Next day it starts to run like crap, once again. WOOT! 
Big surprise right!? 
So back through the ENTIRE fuel system again as its just leaning out after 2500rpms. Fuel pressure checked again, Pulled the injectors off and check filters... Everything looks good.
At this point it gets worse! It starts to lean out even sooner. Its barely driveable. I start checking signals, I double check all my ecu pins arent loose or have bad wires. Im honestly grasping for straws at this point. After spending pretty much 6 hours checking crap I determine that the MAF or ECU is FUBAR. The MAF is a 2V-7V range, and the MAX V I could get out of the MAF was 5V and the min was 1.2V so it was safe to say it was out of range. 
I busted my wad on a $260 reman MAF with a 1 year warranty. Suddenly the car is FIXED! Its driving GREAT! Full RPM range, pulls nice and even. No signs of problems at all!

It drives ok the next morning to work!(yesterday), which is the only time Ive started it in the morning without issue after sitting overnight!

I get to work and decided that Id change the MC out while I had a chance as it was due for its biannual brake fluid flush anyway. I worked late. I left at like 10pm. I made it about 2miles. Above 2500rpms, under load, I get a double misfire(at least 2 cylinders just cut). I pull over and its obvious this time that the fuel is going straight into the turbo... as the turbo is GLOWING! So I let it cool down idling the engine the whole time(without any sign of misfire perfect idle I even checked RPM drop per inj perfect). I drove it back attempting to stay out of the misfire area. Which was hard as that was 2miles of freeway driving back to work. 
I get back, let it cool down, then I shut it off and pulled the plugs. SUPER lean condition. Ground straps were CLEAN! ceramic was bright white! 2 cylinders show slight variance with a slight tan spot where I assume the intake valve was pointed. 
I swapped the plugs out with some plugs that I had put some color on prior and pulled for fresh plugs. This made a slight improvement but the problem was still there. So I parked the car at my work and took my truck home last night at 11pm.

I find it hard to believe that the MAF went out of again, esp when this feels like a 2 cyl miss... but then this could still be a compound issue! My best guess...
MAF is leaning out. I do not have a burnoff function for the MAF, but I shouldnt need it after only 50miles of driving. The Z31 EFI requires the speed sensor for the burnoff function to work(my 81 has no speed sensor).
And maybe 2 of my old used injectors are just not up to par.

However I cannot account for plugs with tan marks as being misfire plugs. Its more likely the other 4 were misfiring but that's NOT what I felt so... bangs head against wall!
And WHAT are the chances that a MAF would work great for 50miles and then suddenly take a dump on me? BANGING HEAD AGAINST WALL HARDER!

 

There is ONE common theme here I did notice, It doesnt go from running decent or great to bad while its running! Nearly every time the car started to run bad, it was the next day after it was shut off... so overnight something changes. The car would drive and be fine until the next morning. Maybe thats just random, or maybe there is something else at work here.

Now in the future I have the warranty injectors coming back, I also have a set of 440cc injectors flowrated coming and a custom fuel rail in the works. And the Z31 efi just needs to get me around for another year as I plan on doing a microsquirt PNP next year. 

I also plan on popping the tank open tomorrow at work just to be sure the fuel isnt spiked or something.

Maybe Ill get lucky and Bernard or one of the other Z31 ecu experts might chime in here and see some pattern that I do not understand. 

 

 

Edited March 19, 2016 by rayaapp2

[FricFrac]

Its tough to do any sort of random and/or intermittent trouble shooting when you can't monitor/data log the system.  A lot of intermittent issues are caused by thermal issues, bad connections/bad ground and electrolytic caps.

 

We've seen all sorts of weird surging issues with the Z31 on the L28ET, etc.  Not surprising since you can't modify a non NisTune Z31 ECU.

 

I would put MicroSquirt on an ATV or an outboard engine - maybe even my VTec Honda lawn mower - not on my L28ET.  If you were running an MS2 or MS3 at least you could data log some of this to get an idea of where the intermittent fault is coming from.....

[rayaapp2]

Its tough to do any sort of random and/or intermittent trouble shooting when you can't monitor/data log the system.  A lot of intermittent issues are caused by thermal issues, bad connections/bad ground and electrolytic caps.

 

We've seen all sorts of weird surging issues with the Z31 on the L28ET, etc.  Not surprising since you can't modify a non NisTune Z31 ECU.

 

I would put MicroSquirt on an ATV or an outboard engine - maybe even my VTec Honda lawn mower - not on my L28ET.  If you were running an MS2 or MS3 at least you could data log some of this to get an idea of where the intermittent fault is coming from.....

Im sure I have bad connections and thermal issues handled.

I run Audi/VW type sealed quick disconnect ends, a nearly new harness.

I run a 23psi stant cap, with the system tested to 25psi.

I might not be able to control the fuel or timing map directly by plugging in numbers, but I have control of the fuel map with a SAFC as stated above. The analog unit allows me to modify currently signal, vs emulation of the signal within a set range like I suspect new SAFC versions do(unconfirmed and maybe wrong I just simply havent done the testing on newer units to see if it will pass the 2-7v range).

The old school Super ITC will also work just fine with the optical L28et sensor... The same sensor it was designed for was used through like 2002 on most nissans, until they finally went a magnetic pickup system. So assuming I can find one, and I am able to get control of the issues here, I should also be able to modify the timing map to a point. 

The z31 is close, but not perfect for the L28et, and thats what those 2 devices were designed for. Trimming in close to better. So though I understand they have their limitations on how they affect mapping, they should be up to getting the job done... in theory.

 

I am nearly done setting up Microsquirt(Microsquirt v3) on my sbc. Microsquirt is nice, I can hide it inside a stock eccs box... and the only sensor I need change is the VAFM(which I have a VAFM housing with a modern MAF inside), add in the Flexfuel sensor and its set. without taking anything apart it looks stock. Which on a '81 S130 in Ca is sneaky... amongst other things. But we have a Mandate coming in 6 years. Alternative fuels mandate, so while Im building my projects Im keeping this in mind. Edit, I know it has it limitations. It was totally designed for exactly what you suggested, but it can totally handle a good old L28 or SBC. There is no reason it cannot handle boost. By that definition, the ECCS system is to low grade for a L28et, as its less capable. But yes there are better systems out there. I actually have a APEXi PFC and a harness that is plug and play for the L28et. I made it from scratch using an RB25det system. My biggest issue was programming the EGR and Air controller into that. I used the output for VCT for the EGR and tweaked the setting, but the idle air signal is incompatible. Actually that wasnt even the biggest hurdle. The system was designed for COPs, which I have, but I have the need to go back to single coil, so I had to make a signal modifier to take the 6 drivers and make 1 signal using, for lack of a better description, a self designed rectifier. 

Edited March 20, 2016 by rayaapp2

[rayaapp2]

After getting back to the car today, I think Ive found the big problem.

I checked the fuel in the tank, checked plugs, compression checked, back flushed the injectors once again to attempt to get any residual that might have been left from the bad filter...

 

Then I checked timing again. And then I saw it. Something simple and stupid. The distributor hadnt moved. But timing was 18* out... 0TDC  from my setting after I max the adjustment on base of the distributor. I spun the distributor shaft gear. Retarding the timing 18+ degrees. I changed the shaft out for another I had and verified it had spun. Im dumbfounded it pun, but its pressed on without any pin. 

[Tony D]

What's your voltage doing to the ECU. JeffP had a HELL of a problem with his promburns and Z31 crap because the early alternators did not give consistent clean power into the power leads for the ECU and that made everything in there go to crap...

 

Once he got good power things started getting consistent again. Same when it was low on gas... AFR's went to crap below 1/4 tank as it was running.

Put a later alternator on it, you got one laying around, right?

[MikerZ]

I just recently completed the z31 ecu and cobra maf setting for the jwt 450 setup, and I installed a maxima alternator with some modification. The voltage is steady and it's pretty good. At first, the car was running great and after I took it for a second drive, now the car won't Rev passed 3k rpm. It's like having a fuel cut off, leaning it out and dropping on its face... But all in all, I do recommend you get a later alternator and install so everything gets proper voltage.