Bean

iTrader: (1)

i apologize for confusion; i've got Bosch plugs at one range colder than stock gapped at .028

and it still misfires

the car runs much better; idles better, etc... but it still starts misfiring in 1st or 2nd right near 4k rpms

i'm wondering if the stock ECU ignition advance is causing problems; because this is where it advances the ignition...
my coil wire on the distributor in the center is missing its clip; the clip broke in half when i was doing something at the beginning of the install; i'm wondering if the clip has anything to do with it

krispytapa

i'm also having this problem. i've finished my na-t project. i'm running ngk 6097 plugs and my fjo is reading 11.* up to 4k rpms then the car starts shuddering. i have the 4wire o2 sensor, whats yours? i'm only using one o2 sensor (bridged ox1 and ox2) and have unplugged the front one. i have the engine code 21 for front o2 sensor but the sensors are bridged. probably because its a 4wire o2.

i haven't figured out the bucking @ 4k rpms. boost builds slow, bov releases, car idle fine. i was told to check for vacuum leaks.

hope that helps. i think we may have the same problem. i'll post again if i figure it out.

MIke

Bean

iTrader: (1)

plugs came in today... havent installed them yet... too dark now

but the car ran right in 1st gear this morning on the way to work
it boosted to 5-6psi and had no miss or big misfire at all; it pulled like a banshee... no spin either...
definitely pulled harder than my 300zxTT did; prolly due in part to the 4.27 gearing in my SC... but damn i can't wait until 2nd or 3rd gear

i've got a nitrous nozzle, a nitrous boost switch, my stock fuel pump; all i need for my alcohol injection is a 30amp relay, wiring, -3an line, couple jets, and a 2-4quart tank
my switch comes on at 5-7psi and just finishes a circuit...
going to have AI done by the weekend

wmulli

Bean, I would get the problems you have (misfire) sorted out before adding more complexity (the Alc injection). If you add the Alc and still have problems (or even more problems!), you just added a lot more hassle to figuring out what the root cause is.

Just my $0.02

SC300T

Bean, what plugs did you get?

Bean

iTrader: (1)

go reread what i posted over the past page; i'm working on getting it fixed... i've got a new set of plugs to install now... and this should fix the problem; i'm getting spark blowout; no doubt about it

Scott i've got a set of NGK 3330s right in front of me gapped at .031; i think i'm gonna leave it that way...

wmulli

Actually, I've been following your exploits with great interest

I was only trying to say you've got to be able to walk before you can run, or in your case, get out of first gear before you go injecting alcohol!

I hope you're right that the plugs will fix your problem, but it seems to me that if you can run it in first, but not the higher gears, there's something else going on...

Bean

iTrader: (1)

well the extra load from 2nd and 3rd plays a big part too

i can sometimes get first to work; but very rarely 2nd and never 3rd...

i'm very very very sure its spark blowout; i'm not running too rich; i'm not detonating... the spark goes out in higher engine load at about 5psi around 3500-4500rpms... sounds like spark blowout to me; and every other person i've talked to as well

gadgetSC

Bean.....Your problem could be foul plugs. You did have some problems running rich and some oil contamination if I remember. I had some of the same symptoms early on. I put new Denso's in and after solving my problems, I pulled the plugs and found lots of crud on them. Cleaned them up and it did solve the break-up you described. Good Luck




gadgetSC-t

Bean

iTrader: (1)

wmulli might be right; the plugs i put in are no better than the ones i pulled out

this is three sets of plugs now

i have also noticed on occaission when i gun it to just move in traffic; sometimes before the stutter starts; i lose my dash lights... thought i was seeing things; but i caught it tonight when going home from work
my negative terminal connector is kinda worn and doesn't make the best connection... tho i figured if the starter could draw enough current; that anything else would too

i wonder if the coil is drawing too much and its causing it to just not fire

because again my car ran right in 1st gear on the first romp with the new plugs; but after that it won't... and damn these plugs idle like ***... so far i'm more impressed with my stock plugs than NGK 3330s

Bean

iTrader: (1)

i'm about to go toss this car in the ****ing river; if i had known i'd have this much undocumented trouble i would have just bought a bike

wmulli

Bean, I can understand your frustration It sounds to me like you're on the right track with it being an ignition problem. Here's some idea's in case you hadn't already thought of 'em...

1) You mentioned your dash lights going out - Bad news!! Check all your grounds in the engine bay! An intermittant voltage can really mess up the computer's readings!

2) Check the plugs. Run the engine up to where it starts misfiring and then turn the ignition off. Pull the plugs and see what they look like. That may give you a clue as to whether it's mixture or spark, or some other fouling. (I know pulling those plugs is a pain in the a$$, but desperate times ...)

3) Make a careful examination of all your ignition wires to see if maybe you're getting spark leakage somewhere. Your symptoms sound like a wet engine, so make sure there's no oil or grease on any of the wiring that could short out your spark.

4) Check to make sure all your sensors are hooked up correctly (O2, etc)

5) Check the MAF to make sure it's clean and the connections are good.

6) If you could get access to a diagnostic scanner, maybe the onboard diagnostics could tell you something.

Hopefully, one of the above will turn up something. If not, I'm sure somebody at CL will think of something.

Hang in there!!!

Bean

iTrader: (1)

sorry i snapped at you earlier; haven't had a good day in more ways than one

i'm wondering if its a battery connection issue when the coil draws all that current...

the spark plug wires have grease on the outside of them and coolant has been spilt into the galley where the spark plugs sit (from pulling the TB coolant line off and spraying everywhere); but i've worked pretty hard at cleaning that up and i can't see anymore coolant in there...

if it means anything the last set of plugs i pulled out looked brand new at the electrode and ground wire... vs the stock plugs i pulled out that were coated in thick oil burnoff

as far as grease or oil shorting out my spark; its possible its leaking from the turbo still; but its not THAT much and i've cleaned the wire boots

MAF looks fine and clean and i've got the O2 sensors bridged at the diagnostic port and haven't had a code thrown yet

i'm going to clean the distributor tomorrow and get a new negative battery cable clamp; i hope its this...

wmulli

Hmmmm... My alarm bells went off when I read this. I know it doesn't take much at all to short out the plug wires. Sometimes even just the residue of oil, coolant, or water is enough to cause the high voltage to jump to the block instead of across the plug gap. Especially at higher rpms/pressure. This sounds to me like what's happening to you. As for how to check for it/fix it, I don't know. With water, just drying it off and waiting a few days for the rest to evaporate seems to work. With oil/coolant, I don't know. Hopefully somebody smarter than me can pitch in with an idea. If you happened to have a spare set of plug wires I think it'd be worth it to try them, but probably not worth the expense to buy some until you know more.

SC300T

I guess my main question is that at that 3500-4500 point, what is your air/fuel ratio????

Spark just going away when you get on it isn't very likely, IMHO... Why would accelerator position affect spark integrity? I know it can happen, but its not where I'd look first. A spark is a spark is a spark. 5psi isn't reallly considered anywhere near high boost. The 3330s aren't going to improve anything at 5psi, you're not at the edge of detonation at that level.

Again, what is your air/fuel ratio?

Around 5psi, you should be *just about able* to boost on the stock fuel system with no mods. 3500-4500 just so happens to be the point where the ECU goes into open loop operation. Can you take the S-AFC off completely? Need to simplify the setup. I'd even vernture to say that you should temporarily disconnect the MSD box to run stock ignition. The simpler the better as far as diagnostics. My guess is that the S-AFC is injecting some bizarre fuel duty once it goes open loop. Again, the stock ECU can go open loop as low as 3800rpm, but can occasionally wait until around 4500rpm.


If you want me to run without my aux injectors, let me know, I can run it at 5psi and get a/f readings off the wideband 02. That could give you some point of reference.

Also, at this point, I'd keep the dwell angle on the distributor in the mid point. The bolt will appear in the center of the distributor's adjustment range (if you don't have a timing light).