nosebleedZ

Clifton, that is a good idea on the AFM while driving. I think the voltage is acscending on Datsun EFI. I'll try that & see if I get the hiccup at a certain voltage. I was already a little ahead of you on the spring tension, I tried it loose (richer) & tight (leaner) on both meters. Either the engine would stall coming to an idle after revving or it would lean out and pop like Orville Redenbachers.

Guys, I have some updates on the car....I have checked the timing extensively-right on. The car starts by barely touching the key. I swapped TPS/ TVS- no change. Readjusted TPS- no bearing on the miss occurring. I actually motorvacced the fuel system thinking I had an injector clogged from sitting-a little smoother @ idle, but the miss is still there! WTF?!?!?! If an 02 sensor is bad it cause this? In my experience, the green light on the ECU will not pulse & the system goes into rich limp mode. The ohm test on the sensor was good, but what the hell? Any other ideas?

Afshin, I have recleaned all terminals & connectors several days ago & used dielectric grease to protect. I have performed a ohm check with no connections showing infinite on the new harness unless the sensor it is connected to is open with the engine off. Believe it or not I have tried one of the spare good AFM I have in my garage- slight change for the good but it just moves the stumble down the rpm band about 200 rpm. I believe this is due to the size difference in the turbo AFM housing & the N/a AFM. I could try a third one I guess. And yes, the miss/ lean condition is rpm dependant wether the car is driven or while in neutral. When revving the A/F guage will stay stoich range (14:1) until 1500, drop to way lean (17:1), miss almost simultaneously, then majically at 2500-take off & rev to 6800 or so. The real rub though is that it stays stoich the whole time. Before, it would even go slight rich (13:1) when revving in neutral. The SDS computer is set to fire the additional injectors at 0" vacuum & beyond (psi) and varies gain dependant on load input from the distributor negative lead (rpm) & by boost pressure (psi). It can be set for 10 to 80% injector (s) duty cycle by a gain knob. Any other ideas? This thing is gonna be the death of me!

Is the Tec 2 unit OBD-1 or 2 diagnoseable? I actually have a guy that I met in Knoxville that was running a F.A.S.T. ECU on his S30 turbo and the system was OBD-1 scanner compatable. The SDS unit I looked at, I think has OBD2 and an optional UEGO wideband setup for a grand or so. I would really like to upgrade,but I honestly don't think my problem is in the Datsun system currently. I need to pinpoint this gremlin & maybe go standalone afterward. I would hate to change everything & find the same issue. Based on my first post, ever have anything similar before or after EMS? Tomorrow I'm going to try some more timing adjustments as recommended by Warren & Cygnus.

Well sweetleaf, that is a good question really. The SDS system has been wonderful since I've owned it. I can stay out of the throttle & literally get 21 to 24mpg and when I want it and the boost guage reads 1psi hundreds of additional horses gallop to life (at about 8-10 MPG LOL!) This system is actually a carry over from my first turbo build. I know the stock EFI is antiquated and if I do end up on a standalone it will probably be an SDS EM kit. I know alot of guys on here use MS controls, but there are so many posts I see with soldering this, retuning that, diagnosing this,....i honestly am a little leary of it. If some of you have hit a home run with MS, I might consider it if the wife won't divorce me. I have probably $25,000 in the car already with me doing absolutely everything. What is your experience with various standalones? Also any input on my lean condition?

Yes ,Rags, I verified it with the meter....continuity @ idle/ 35* throttle angle & it goes to infinite. In reverse the WOT switch checks OK too. Any other stabs at it....I'll take 'em! Thanks for your question.

Thanks for the suggestions guys, it almost does seem to be timing related. And I know where you are coming from on the "factory " turbo timing on your cars. It is *20 BTDC w/ the ECCS system. On a non-turbo it is 5-10* BTDC with total advance at WOT of about 30-35 degrees BTDC. I have run the timing as an N/A with an inline one way valve to limit advance when boost comes on. The funny thing about this is that I ran this setup with no issue for two years! I will try to advance the dizzy some more & see if that helps/ or hinders matters. I'll post my results today and again, thanks guys for steering me in another (much needed) direction! -NosebleedZ

Do you have pics?

No, I thought the n/a ECU had only provisions for narrow band width. I am using the stock sensor with stoich guage.

I tried to post this earlier but my computer did something funny. Anyway, I have a 79 zx that I have been working on the past year-majorly overhauled everything-body/ paint, engine/ tranny, interior, etc. I have the car 95% complete but I have an engine miss/ lean condition from 1500 to 2500 rpm. The car idles fine, revs good past this point, has steady vacuum (18"), everything is pretty much new. The A/F guage goes to about 16:1 or less at this rpm under load or revving from an idle and when it smooths out an revs it is still on the lean side of stoich. I have built and modded Z cars for about the last ten years & was a dealer tech on Nissan vehicles prior to that. In my experience with these cars, I've never had one with a gremlin that I couldn't find in a few days, so I'm stumped & a little embarrassed. The mods to the engine are as follows from current rebuild be me: F54 block-Ross 2.8 forged pistons/ chrome rings/ stock rods & crank/ trimetal bearings, MN47 head- port polish/ seals/ springs/ Msa turbo cam/ chain & gears/ Cometic gasket 1 MM, SDS additional injector computer w/ 750 cc injectors, 270cc injectors on rail, Garrett GT3271R ball bearing turbo, 4" thick vertical core I/C, N/A dizzy, N/A ECU, new ECU harness, new sensors-all, except Turbo MAF w/ N/A guts, narrow band O2 w/ A/F guage, RRFPR, FD3S BOV/ bypass valves, Walbro 255 lph pump, 60mm TBI upgrade, 2.5" DP/ exhaust. All tune up & engine parts are new-not joking. The tests I have run include FSM EFI checklist, EFI component checks, injector pulse tests/ dizzy input, fuel pressure-36 psi @idle/ 58 psi @ WOT, stethoscoped entire engine bay for vacuum leaks, reclocked dizzy/ oil pump 5 times-returned to original setting because it made it worse, FSM EFI relay checks, leaned & richened by MAF gear position-made worse. Swapped ECU's 3 times, MAF once, & cleaned/ greased/ reconnected all harness plugs. Base timing is 5* BTDC & 18* w/ advance connected. Oh yeah some other oddities: the plugs are sooty black (rich look), car can take 5 seconds to crank before starting when cold-intermittently, & tailpipe smoke is non existant, even on cold start? With all the knowledge on this site, I need someone to point me in a direction I have not been. Thanks, NosebleedZ

Hey guys, as stated in the title, I don't think I can see the trees because I'm standing in the forest! I have a '79 zx with the following mods: F-54 block stock bore( Ross forged w/ chrome rings, stock rods, tri-metal bearings, stock crank, etc.) MN-47 head with fresh port/ polish/ seals/ Cometic gasket, turbo cam, etc., Garrett GT3271R ball bearing turbo, Vertical core intercooler 4" thick, Walbro 255 lph fuel pump w/ filters, 270 cc injectors in the rail, 2 each 750 cc injectors fired by the SDS piggy back computer, 60 mm TB w/ Datsun TVS, zx turbo MAF w/ N/A guts, other sensors are stock (new though), narrow band 02 w/ guage, twin FD3S diverter valves, N/A 82 ECU w/ new replacement wiring harness, new cap, rotor, wires, NGK plugs, coil, condensor, N/A dizzy, EFI hoses, new starter, alternator. That is most of the engine mods that come to mind, other than "one off" spacers, adapters, etc. The engine has less than 25 miles on it with no leaks since I rebuilt it. The problem I am having is a lean miss from 1500-2500 rpms. The car idles fine and revs OK under load past the stutter. The base timing is set at 5* BTDC with advance unhooked. Noid light is giving good pulses that change with load & rpm. I have used the FSM to check all EFI curcuits, relays, etc, & passed. I have tried 3 different ECU's with the same result. Fuel pressure is 36 psi @ idle & 58 psi @ WOT (RRFPR controlled). Checked dizzy to injector pulse relation (3 fires: 1 pulse)-seems OK. Screwed with MAF wiper and resistance tested-OK. Readjusted valves, reclocked distributor/ oil pump 5 times-small changes for the worst usually, so reset it back. I have used a stethoscope to listen for vacuum leaks for hours with none found-boost guage hold steady at 18" of mercury. I am at a loss. The same system (minus the turbo & intercooler upgrades) ran flawlwssly for 2 years! I have rebuilt & modified datsuns for the last ten years, heck I even worked as a tech on Nissan vehicles for four years before that.....so I'm stumped, discouraged, tired, & a little embarrassed that I cannot find this gremlin. So please, masters of Hybrid Z's, yank me out of the forest!

datsun, I will e-mail you this info, cuz you have probably already left on your trip home. Roger & I have done business for several years and are friends of sorts, & YES..he is very hard to get ahold of! He has moved his office into his home over the past year or so. But I know how it is when you need that obscure part from him yesterday. Try this #, he gave it to me till he gets his 800# up & running correctly. It's 865-995-0443. I hope this helps.

Congrats Phil. I bought my wife an '05 G35 Coupe for our tenth anniversary & her birthday, they are really close together. She & I love the car! It's 5 speed auto (you'll love manual mode- it upshifts & downshifts in a tenth of a second with the flick of your wrist), diamond graphite paint, 18" wheels w/ Nitto NT555's, & loaded (tint, nav, LSD, etc). The cockpit hugs you, the exhaust note caresses you, the looks of the car gives pedestrians whiplash & the 300 horsees get you horny;-) ! The best thing is it's a 2+2 350Z with twice the luxury. You can also do tons of mods to them. Her's has AEM intake system, Skunk2 power plenum spacer, & Greddy cat back exhaust (good for 50 additional horses). They make a twin turbo kit for these that is good for 700 whp on stock internals! Welcome to the fun of owning the 350z's handsome big brother!

I second Vashon's diagnosis, this happened to me a few years back. It's either ECCS/ ECU fault or distributor. This is an ignition problem, not a fuel problem even though they correlate for injection timing. Stock Z EFI ignites the mixture every third injection in the cylinder. If the ignition signal (input from tach negative signal wire) is erractic, distributor optical plate is bad (dirty), or the coil/ module is bad, it will cause injections to be to early (a whipped pup to 4K & the pull hard past this from an overrich condition) or too late (pull like a banshee till 4K & then hit a wall). Both of these scenarios will cause a bad fuel odor, as well as give suspect plug readings. This is difficult to troubleshoot without a factory shop manual/ disc or ECCS/ EFI analyzer. My problem was a bad input from the MSD box, but I have seen this with the factory ignition module as well. I hope this help! Been here, it sucks. Z electronic gremlins are an acquired taste....LOL!

Garrett, I had a similar problem about two years ago. I think your ignition pulse is erractic. I don't post much here (I like to read mostly), but I've seen this a few times in my ten years of owning, building, & bleeding Z's. If you are running a stock configuration ECU (ECCS or EFI), the ignition fires the mixture on every 3rd injection pulse (ie., half of cylinder fuel-intake stroke (one injection), second half of cylinder fuel -power stroke (two injections), spark ignition & cylinder saturation (cooling during explosion). If the incorrect injection pulse to ignition ratio is upset, for instance fires the mixture too early or too late, then the car will smell flooded from the stray 3rd injection or the beginning of the next injection cycle. Basically, power will suffer either way. It will pull like a banshee and flatten by 4K from cylinder starvation (early) or will be sluggish from idle and hit it's stride @ 4K & pull to redline from the overrich fuel. Unfortunately this is difficult to troubleshoot & it usually ends up being a bad ECU or distributor. But the FSM has a voltmeter test to determine which one. I can probably find it for you. Mine ended up being the ECU. The engine sensors & negative wire from the coil (tachometer signal) triggers injector pulse through the ECU. I hope this helps some. These cars will drive you nuts with analog EFI gremlins! I've been there many, many, times.

Thanks 510, I will try to contact them concerning the fittings. Yeah, that is the turbo, if you can believe it, I traded an MSD 6BTM for that turbo (it was brand new, though). I think I came out decent for a trade. Do you have any ideas for the downpipe? Or a T-3 flange?

Hey guys, I picked up a Garrett GT3271R Turbo on a "horse trade" & this thing is HUGE! The compressor housing is 9.5" (says .70) and it has a T-3 exhaust snail (.82 AR). I've got a new L-28 engine project this winter for my '79 ZX hardtop, and was curious about expected power or flow from this thing if anyone has used it on a L-6? It is a water cooled/ BB center section unit. I will have to move it forward about 4" in the engine bay to clear the strut tower and put it where the A/C compressor once lived. I also have a question or two, or five about miscellaneous parts & such for the install: 1)where can you buy the oil feed and oil drain fitting (bolt on, no threads)? He didn't have them. 2)where can I find a T-3, 4-stud downpipe 2.5-3" (straight, unlike stock DP)? 3)where can I find a T-3 outlet flange to weld to the front lower section of a stock turbo exhaust manifold? 4)what is the acceptable axial play of a BB turbo cartridge? This one will move a little less than 1 mm when rocked up/ down, side to side but does not contact the housing(s). Rebuild? 5)I need to clock the exhaust snail, and I don't want to damage the impeller, it's stuck with the bolts removed. Is it a torch & mallet job for two guys? Thanks, and appreciate all input!

That really stinks, man. I know how hard it is to repair the rear of the S130 cars. Nice car though!

If you haven't had any luck with the other suggestions, I would bet you have a radiator that has some age on it. Severe electrolosis and corrosion at the end tanks (inside the rad) will cause the agony you describe. I've had it happen many times over the years. Brass, aluminum rad makes no difference! Copper is actually the best a thermal disipation. It's a $35.00 fix.....remove rad, take to rad shop, have "boiled", & reinstall. Your 230 degrees will magically become 170 again. If you want further cooling (if you live where it is miserable in the summer) buy a 150 degree t-stat from NAPA. They are the only ones that carry them. They will not be able to look it up though. Have them pull up the part# of the stock Z t-stat and transpose the heat range digit to a 5. It's about $9.00. My temps never come above 170-ish in traffic, or 160-ish at full boost. Hope this helps you before you contemplate suicide or torch your Z investment!

I live in eastern Tennesse which is where most zx cars were apparently sold and laid to rest. I have a friend here that could get you a great deal on a used N/A motor or even a complete turbo motor w/ all electronics for a little more. But I TOTALLY agree with the other guys, black plugs are 90% of the time not the engine, but the EFI. Have it checked before spending a dime!

The most dissapointing thing about that show was the 17 or 18 second 1/4 mile time AFTER the mods to the Z's! The guys that were racing must've been pulling out in 2nd????

I experienced that once with a plugged valve cover breather. If yours is a K & N it might need a cleaning.

Lewis, I'm new here, but I was wondering if you have thought about Lexan rear windows/ going to a manual rack/ do some holesaw work? Some of these are great weight reduction tricks.