Edit #1: checked resistance from battery negative terminal to unpainted chassis screws and various points on the block, and it was always at or close to 0.. so that's not it
Hi everyone - just a warning, this will be a long post. I've tried searching, and found bits and pieces (including the awesome "OMG SAME PROBLEM AS MINE! oh.. no one ever replied..." threads) but nothing that genuinely convinces me they have an answer to my woes. I'll try for a useful TL;DR at the top & bottom, but no promises..
First off, I have a 5-speed '93 fastback non-SE with a KA24DE with 260k on it - the block itself is a sorta-rebuilt (didn't touch valves/springs/pistons, changed pretty much everything else) S14 block/head that I swapped in at around 220k. That engine had 80k on it then, so now there's only about 120k on it now. S13 cams/intake assy/exhaust/everything else really (needed to make it OBD1 and smog legal, didn't wanna use crappy S14 cams). I've always run 91 octane, since before I even swapped in the S14 block, and often times throw in octance boost and even 100 octane when I feel like pretending it'll push it to 300WHP.
Quick note: about 1.5 years ago, I passed smog with incredibly low numbers using the above engine with all mods listed below. I had put about 10k on the S14 block at that point. I haven't really changed anything since, aside from typical tune-ups.
As far as mods/etc:
I have a K&N cone filter (just cleaned, can eat out of it at this point), custom 2.5" exhaust (downpipe-back), larger MSD ignition coil (tried going back to stock coil, no change), electric fan, some kind of what seems like copper radiator (had it for forever, never had an issue - dude swore it was a 93 skyline rad but I never checked), bypassed intake air temp sensor (some California-only emissions thing - was throwing a code so I just stuck a resistor in there), removed that intake silencer box and capped the connector on the main intake line.
What I've checked:
Since these problems have appeared, I've put in fresh oil, oil filter, fuel filter, coolant (was clean when drained), plugs (NGK Iridiums, factory gapped - tech swore up and down they were gapped to spec but I honestly lost my feelers and haven't checked - but the problems were all here before I changed them - new plugs had no affect), and tried swapping in a different dizzy/wires and they had no affect either. Tried the 3-part seafoam technique a couple times as well (1/3 in gas tank, 1/3 in oil - drive 15 miles - change oil, 1/3 sucked in through brake booster while engine running - tell the neighbors/fire truck there really isn't a fire). Checked EGR, and the engine bogs/stalls as I squeeze it, so I think it's fine. The accordion-piece thing seems fine - It looks pretty cruddy, but I couldn't get water through it anywhere, and can't see light through it anywhere if I pull it as straight as I can without breaking it, so I think it's fine. Checked plugs after changing, they're pretty much clean. No foam in oil, no crud in coolant, always starts fine. Running 20-50 conventional "race" oil atm but have been using 5-30 pure synthetic 'til now (tried the thicker stuff on a recommendation from a friend, honestly it sorta seems like it helped but not much). Swapped O2 sensor with a known good sensor with no affect.
Can't think of anything that I missed that might have an affect.. I apologize that this has already become a novel if text, but I'm desperate.. so here goes the list of problems:
I've got what seems like a combination of issues going on, and have to get my poor car smogged by next week (tags expired, got pulled over for it a couple weeks back) and just can't seem to figure this all out on my own. It seems like with everything I try, if it works at all, works for about 1 minute to 1 day and then goes back to have the same issues.
I'll try and separate out the issues:
1) Erratic idle, in just about every sense of the phrase. Cold startup usually is around 950, warms up to 750-800, driving around might be ok, then suddenly it almost stalls coming to a stop then idles at like 550 when stopped - but other times while decelerating it will stay at around 1100 and stay that way once stopped, and not bog down at all (usually when this happens the idle remains high until I cut the engine, then it sometimes goes back to normal). I tried adjusting the screw (with or without the TPS unplugged) and it changes, but often times even with the screw COMPLETELY tightened the idle remains overly high (only ever tried adjusting while car is warm). I removed and cleaned the screw, sprayed carb cleaner into the assembly, and into the throttle body, cleaned the MAF with MAF cleaner, tried removing the larger vacuum line on the main intake right before the TB and sprayed cleaner into that (usually the engine cuts once disconnected but I just kept starting/spraying/starting). The dropping idle coming to a stop screamed vacuum leak to me, but I tried for hours and couldn't find one. Idle stays fine while depressing the brake while stopped. Idle issue ties into the next issue:
2) Sputtering/puffing/putting. At idle, it "puffs" and "putts" sometimes (usually more-so when warmed up). While accelerating (and only while under load/moving - never while sitting still out of gear), the car almost always sputters 2-3 times at just before 1800 rpms, right at 1800, and just before/at 2000 rpms. If I sustain about 2000rpms it sounds almost like a chronic hiccuper is having a seizure while gargling a mouthful of water and marbles (should be pretty descriptive). While decelerating and leaving the clutch engaged, it sputters at about the same points on the rev band. Under WOT it's almost always fine but -somtetimes- sputters going up the rev band randomly. However, if I accelerate just right (slowly applying gas, like you'd normally do I guess), it sounds kinda like a sputtering motorcycle all the way up to about 4000 rpms - sounds a helluva lot like the guy describes here: http://answers.yahoo.com/question/index ... 932AAOrKJO. Timing was a recommendation there, and leads into issue #3:
3) Can't time it for s***. Or, in a more descriptive sense, with the TPS unplugged I can't get it to hold an idle even close to long enough to establish an average timing, and even when I think I do, the computer seems to "change" it anyway, regardless of whether I adjust it with the TPS unplugged or not. I followed what I thought was the factory method, as described here: http://wiki.answers.com/Q/How_do_you_time_a_240sx - though I was told that 20 BTD is the last notch (meaning +5, 0, -5, -10, -15, -20 actually being the 6th notch, as opposed to the 5th as given in the article), so that's what I've been shooting for. But, while trying to time the engine the idle goes crazy - when I unplug the TPS it just goes s*** insane (acts like someone keeps pressing the gas pedal in 2 second intervals) no matter how much I rev it or let it sit. If I tighten the IAC screw all the way, it still only goes down to about 900-1000rpms. If I leave it screwed tight and reconnect the TPS and drive around, it starts idling at about 5-500rpm and stalls a lot (but it takes about 2 minutes of driving around before this happens). If I try and be dumb and mess with the dizzy while the TPS is plugged in, it seems OK for a bit and then goes right back to running like crap.
If I just cut the engine, disconnect that battery, and just arbitrarily pick a position for the dizzy and turn it on, it magically seems to come to life for awhile, but then the computer decides it'll have none of that nonsense and "corrects" the timing for me, thus returning me to a state of crap. Tried giving the computer the bird and swapped in one from an AT 93 s13, but it didn't solve anything (since moved the MT 'puter back in, as the other wasn't mine). Thinking I may have just put the dizzy assy in a tooth off or something a couple years ago, I tried removing, turning, and reseating (difficult to know for sure which tooth you're on while the engine is assembled, as you have to kinda twist and shimmy it into position), which only resulted in an un-start-able engine.
I've noticed that the sputtering described in #2 happens pretty much regardless of what the timing is, leaving me even further perplexed. At around 25 advanced (what looks like it'd be one notch past the last visible one), the car pulls and roars like a champ at 4K+, but still sputters - especially so at near 6500 rpms. Also worth noting - it generally just smells like it's running rich, but not much. Warmed up at idle, it's almost scentless, but only rich after coming to a stop with the clutch engaged (which I'd expect, but it kinda smells more rich over the last few months than it used to).
I've tried "starting from scratch" with the timing - clearing the ECU (always only has the 55/ready code), warming it up, -trying- to establish the idle to 750 (runs like crap with the TPS unplugged but I check the idle after re-connecting and re-starting, then killing engine and re-unplugging), and adjusting dizzy - but the idle issue defeats me quickly every time. Again, no matter what I do, the sputter never goes away.
I can't pass smog with the idle all over the map - 2 different shops turned me away while I was sitting in the parking lot. Nice guys, I suppose. Better than running me, showing me awesome numbers, but telling me I failed anyway because the idle is in the middle of a random-drug bender. The timing is never quite right anyway. I've got the S14 block's intake assy in the garage, but I'm not sure if anything on there would help. There are other things I have yet to check, but I can't do any more tonight and am just hoping that someone will read this in the meantime and say "OH HEY IT'S JUST THE _____ YOU DUMB-a**", or something to that effect. If I don't hear anything, I'll proceed on and update as I find results.
What I haven't checked yet or done:
a) The grounding mod described here: http://zilvia.net/f/tech-talk/190745-ir ... -kade.html. I plan on doing this tomorrow, and expect it to help my idle at least somewhat, but am not sure if it will fix #2 or #3
b) Replace dizzy - seems a bit crazy as it runs like a champ during 95% of the time, but I've been told by a few people to try this.
c) Coolant Temp. Sensor - I hear this can cause some of the above, but not all. I have the CTS from my old block and the plug housing looks pretty new, but I don't happen to have any coolant in the garage to throw back in after removal so I just haven't tried it yet.
d) Remove dizzy cap, plug #1, and manually time the engine by rotating the crank and twisting the dizzy until it all lines up right at 20 advanced - I was thinking of trying this but figured the ECU will just kick me in the junk for considering it and waste my efforts away as it adjusts timing back.
e) Replace engine - seems like I just did this, damnit
f) Replace car - as much as I'd love a bone-stock S14, it's hard to find someone that would do a straight trade for a non-SE s13 fastback with 260k on it (if you're interested, feel free to PM me of course). Aside from that, I'm practically broke.
g) Replace IACV assembly - sounds practical, but it's quite expensive and will take a lot longer than I have time-wise to receive in the mail according to the couple of guys I've asked about in town. Also, see last sentence in f) above.
h) Smog hook-up - again, see last sentence in f) above ($40-50ish for a legit smog plus reg fees is gonna push my bank as is).
i) Check/replace injectors - totally plausible for some of the issues, but considering I can almost set a clock to the stuttering, it seems like it may not be the entire issue. Gonna test my injectors tomorrow-ish as described here: 92-240sx-se-coupe-at-low-idle-bogging-d ... 30269.html
It's worth mentioning now that I just had a baby and have very little money to my name - so I'm not gonna be able to go buy a new head and "just to try it out and see if it fixes the issue" - I totally understand that I'd eventually solve the issue this way, but I just can't do it. I know there's plenty on this chassis that needs replaced, but I also know that replacing my motor mounts/suspension bushings/driver seat/changing my diff. gear oil/upgrading to 300zx brakes/turboing that b**** is NOT going to fix my ignition issues (would love to do the last one, but I fear my motor will quickly imitate this: http://www.youtube.com/watch?v=aUkXriHjQeI .. and considering I'm trying to pass a legit smog right now it's out of the question anyway).
All that said, I have a good amount of additives/oil/random 240sx parts laying around, including a '90 shell (KA24E long gone), and my original '93 DE still (pretty sure it needs a new HG and a list of rebuilt stuff) to play around with. Advice would be greatly appreciated, of course. Help, please!!!
TL;DR - KA24DE with erratic idle (surges/stays over 1000 with TPS unplugged and IACV screw tightened all the way, otherwise it just spins a wheel and throws a dart at a number it will stick to until next time I start the car), sputters and stutters at around 1800 & 1900 & 2000rpm, impersonates a two-stroke engine full of water sometimes when pulling slowly from a stop, and attempting to time the engine is becoming a legitimate macro-demonstration of quantum indeterminability.
