MaDMaX024

ok, so since i've put my motor in, i've been working out some bugs throughout the car. i've got pretty much everything under control except for this stupid idle thing(and a few other things i think are all the same problem).
it starts every time and stays running. also the warmup cycle is fine.
once its warm the idle is VERY inconsistant. sometimes it'll be solid at 1500rpm. other times it'll be 600-800 (slow fluctuation, almost like a very weak stumble). very occassionally it'll be rock solid at 750rpm.
also, looking at my EGT guage, when its nice and smooth at 750 the EGT reads ~600*F, the rest of the time its 800-825*F regardless of idle rpm.

now, i went nuts and tested alot of things and even pulled the intake manifold off (unrelated, but i need to port it to match my spacer).
so far this is what i've tested: MAF, injectors, coils, TPS, closed throttle sensor, power transistor, cam position sensor, idle control valves (currently off the car, they are both electrically and mechanically good), coolant temp sensor (the one the ECU reads from..the guage has always worked fine), swapped ECUs into another 92se 5spd and it ran fine, the plugs were fine 4700 miles ago when the motor went in the car, knock sensor is perfect, VTCs are rebuilt and fully functional.
i have no vacuum leaks (pinched blowby hose along with replacing all other vac lines), fuel pressure is a little high (45-47psi@idle, 57psi@W/O vac applied), cooling system is topped off and the air has been bled out.
i have removed my EGR system (block plate, welded the tube shut, disconnected solenoid and vac lines, plugged everything...this eliminated my random bucking problem in every gear) and i'm in the process of removing the EVAP system (just need to plug the lines, but the manifold is off so its not a rush to finish it).
my battery is in the trunk.

couple things i was thinking, oxygen sensor could be the culprit but i'm curious as to why it would mostly affect how the car idles.
when i moved the battery to the trunk i had some grounding issues and didnt get completely resolved, i dont think this is it either because it ran like this before i moved the battery.
finally fuel pressure, i could see where this would be an issue but why would it be this inconsistant?
so now i ask all you gurus to help me out, i'm willing to do pretty much anything. if i'm going to replace my o2 sensor i need to KNOW that its bad. as far as the fuel pressure goes, anyone know of a cheap adjustable regulator?
any other suggestions?
my timing is advanced but i'm not sure how much (no functional timing light, yah its a big no-no, i'm already aware)..i retarded the timing and it just sputters on sudden stabs of the throttle, so i advanced it until the sputtering went away.
if it helps any, when holding a steady speed in first gear, the car bucks like a wild bull, also when decelerating in second gear (not as noticeable in 3rd/4th/5th) its most noticeable from 2500rpm and lower.
another helpful tidbit of information, if i hold the throttle steady at 2300rpm w/o load on the motor it'll quickely cycle from 1500-2300, like its rev limited to 2300, but as soon as i give it more throttle it stops hunting.
like i said in the beginning of the post, i'm pretty sure everything is related but the 3 things i suspect to be the problem dont make any sense.
any help is greatly appreciated (IMs also work, i can test stuff in realtime )

MaDMaX024

another thing, when the cooling fans come on, it does NOT idle up, it just drops down to about 600, then slowly (in steps) creeps back to the usual 1000rpm idle. i've also removed my a/c system and for whatever reason i cannot get the fans to come on with the a/c button (probably has something to do with the connector not being plugged into the compressor)

MrGone

iTrader: (30)

your timing is probably still pretty retarded (maybe 10*?)

When you go to set base timing unhook the grey throttle body connector and the purple connector under the throttle body.

All the EGR does is pull exhaust gases into the combustion chamber to lower combustion chamber temps.

MaDMaX024

i've advanced the timing all the way and it has very little effect on the idle.
if it were as simple as everything being clean and me having a consistant high idle, i'd just turn the screw so it dropped down..
nothing has any effect on it, the TPS setting just raises it..
i know the EGR can F'up the way the car runs if its not functioning properly, i just didnt want to hear suggestions of things i've already done

:angry: stupid car!

MaDMaX024

bump bump bump

rimmer1

Hey, I have recently encountered the same problem, but only when the car is warm. I have just done an oil change and put in fuel injector cleaner. I also have the same problem with jumping in first gear but I have not increased the timming. It has rained here for the last week, so hopefully that is my problem!

MaDMaX024

mine does it in the dry, i refuse to drive my car in the rain (no splash guards at the moment, terrible tires)

Jeff92se

iTrader: (82)

Get the fuel pressue under control. Any one should do
Might as well get a new 02 (if that one isn't new). You spend all that money on other stuff already.

MaDMaX024

how do you suggest i get the fuel pressure under control? best option i've seen is the $100 nismo regulator from the dealer, i'm looking to spend as little as possible.

Jeff92se

iTrader: (82)

Sard/Aem or any of the other fprs used by the boosted guys. The Nismo unit is nice because it looks like it will fit our oem fuel rail. But pricey and the specs are unknown. What are the specs?

jwmaxse

iTrader: (1)

You could buy one from an .org member if they have one. Even if it is used, they could tell you if it was working or not. I think there is a proceedure for checking a FPR (fuel pressure regulator) at autozone.com. Here is the link: http://www.autozone.com/servlet/UiBr...3d801f5181.jsp Maybe one of those vacuum lines shouldn't have been plugged or something. That's all I can think of.

MaDMaX024

i've swapped in a known working FPR and it made no difference..the pressure was high right after i had a walbro pump put in, so i know its not vac line related.
i'll post in the classifieds for an adjustable FPR.
i still dont think fuel pressure is the problem, its way too inconsistant..or maybe i'm missing something..who knows.

MrGone

iTrader: (30)

DanNY was selling one a while ago, I dont think it ever sold. Might want to PM him

jwmaxse

iTrader: (1)

Yeah, it definitely sounds like more than just the fuel pressure, but I guess all you can do is take care of one problem at a time. I think the fuel pressure is supposed to be like 38 when idling and 45 when you give it some gas. If the exhaust gas temps are low I think it means you are running rich, but they are high you are running lean. I think they are supposed to be at 800 and something, but that's just a guess. I don't know, maybe it is running rich and then the O2 sensor is trying to compensate for it, causing it to jump all over the place. Just a thought I guess.

MaDMaX024

the usual idle temp is 800-825*F, but when it runs good, its ~600*F. it just doesnt make any sense.

jwmaxse

iTrader: (1)

That's weird, sorry if I haven't paid attention to any earlier threads of yours, but how was it running before you rebuilt the motor, actually, did you rebuild a motor or just replace it with a different one? I'm not really a mechanic or anything, but I would just take it one step at a time and fix the fuel pressure first. I do know that the O2 sensor readings will cause the computer to try to compensate if it is burning too much fuel though. Have you tried pulling the CPU codes yet? Mine was throwing my KS code for a few months and the engine light never even came on, but maybe the codes will tell you something. I know it is frustrating because I have been trying to fix mine for a while and it should be done early next week when I get the part in. I hope you can get it running right soon. We gotta keep those black max 5sp SE's running right you know!

subs1000w

i would get the fuel pressure under control befor you replace your O2 because "if" your running rich which you have to be at those pressures it will foul your new O2 also

and i think running really rich could cause alot of your problems

57psi is what alot of the boosted guys with FMUs are seeing

subs1000w

you could try this one but youd need a fuel rail adapter fitting

http://cgi.ebay.com/ebaymotors/ws/eB...category=33553

MaDMaX024

i had the motor rebuilt..just a normal rebuild with 300zx pistons (NA, 10.5:1 compression, nothing special) and rebuilt VTC.
i forgot to mention that i have checked ECU codes and it comes up "55" which means nothing wrong.
i think in the meantime while i hunt for a cheap adjustable FPR, i'm going to do a ground kit since thats almost free with my resources.
reppin' the VE 5spd POWAH(now if only i could keep that power on the ground instead of melting my tires off i'd be all set)..hahaha

MaDMaX024

i understand what you're saying, but it doesnt make sense that it'd be this inconsistant. i guess if its a combination of bad O2 and high fuel pressure..but still why would it randomly run perfect?
also, how about the wierd rev limit thing at 2300rpm?
i know, i have too many problems

Spipedong90

The EGR does make sense though. If it's there to lower your exhaust temps, and the car only runs properly with lower exhaust temps: That sounds like some sort of relation to me.

MaDMaX024

well my EGR was fully functional before i did the motor swap and it hadnt changed much after except the exhaust gas tube would not seal against the valve. i removed it and noticed that the car ran better because it didnt have that leak anymore(before i removed it, i sealed the leak with 5 minute steel, then it started leaking again).
besides..what has EGR ever done for me besides make my intake manifold dirty?

jwmaxse

iTrader: (1)

Well, it does lower the combustion chamber temperatures and help keep the motor from pinging. I don't think this would be your main problem but it is actually an important part of the motor. http://www.asashop.org/autoinc/nov97/gas.htm
You probably already know this because it sound like you do your own motor work, but this site has a good explanation of how important the system is.

MaDMaX024

i understand the function but i've even monitored knock sensor output after the EGR was removed, nothing changed(its funny after reading that article, my ECU doesnt see any problem with the EGR system even though its not on the car anymore). i'm searching for a better price on an OBX adjustable fuel pressure regulator now, then i'm gonna clean my oxygen sensor off if theres soot or any garbage on it and see how things go. if this doesnt fix it, then i might break down and find a mechanic that is willing to work on my monster.

jwmaxse

iTrader: (1)

I hope things work out for you, you know it is serious when you break down and have to go to a mechanic.

Jeff92se

iTrader: (82)

EGR systems are designed to reintroduce exhaust gas into the combustion chamber to help reduce the temps(this was said before by Keelan). I don't think it's the cause of your uneven idle. I'd fix the fuel pressure problem first. Even if it's not really the problem, you should fix all known problems first. It's not an expensive fix anyway. Again if the O2 is old, I'd go ahead and replace it. I mean you just spend how much $ and effort? You should go all the way with a good known O2. Could also still be a vacuum leak or something funky with the AAIC

MrGone

iTrader: (30)

I said it first


Really though, I would be really surprised if it is the EGR causing the problems. In some cases disconnecting the EGR can cause an engine to loose power because the combustion chamber temps grow too hot, but thats normally on all iron engines.

I know it doesn't make sense, but it really sounds like the same idle problems I get when I ground my VTC's. The thing is though your VTC's are good, so it doesn't make any sense.

Exchange the timing light, check/set your timing just to make sure. Probably not it but its nice to have all your bases covered.
What were Julio's FPR readings again? (Also what were Matt's? I forgot)
I know the O2 is coming so we'll have to wait and see with that. The thing that is kind of surprising its the car is having a hard time holding an idle with a load (headlights or like your saying, the radiator fans), so maybe the high fuel pressure is making it hard for the ECU to get the car to idle correctly, if that makes sense.

All the exhaust leaks are fixed, so hmmm. I remember the one time I forgot to hook up my EGR tube the car didnt idle well, hooked it back up and its good now.

The 2300rpm thing is strange though.

MaDMaX024

i know the EGR isnt the problem because when i took it off it ran better..just like it did before the tube started leaking. i know the EVAP system can cause some idle/surging issues but with that gone, i'm not too concerned about it.
why fix it when you can just pull it off and simplify it?
fixing the fuel pressure is more expensive than fixing the O2 (unless you can show me a good adjustable regulator for less than $60 shipped) but it needs to be done regardless.
i'm positive i'll see some sort of positive outcome from changing the O2, but i want to make sure i dont F'up a new one because of something else...i'm not band-aiding it this time..this time next year i want 400FWHP on 12psi and i'm not gonna chase down little things when that time comes, it needs to be perfect before i start daily driving it again..the damn thing has 4600 miles on it (motor/tranny) if its not running perfect, then i'm not going to drive it until it is.
if you have any unorthodox tests for the idle control valves, please, let me know. they ohm out fine and they're physically good so i dont know what the deal is with that. remember i have no a/c and it wont idle up when i press the button. even when i had the a/c belt off with the rest of the system connected it would randomly try to turn the compressor on and idle up (however i never had a problem with it when the belt was on).
jeff you should IM me sometime. shawn'll tell you, its alot easier to figure things out on AIM.

P.S. as far as the vac leak goes, i've chased down all that i could hear then pinched the blowby (PCV) hose with vice grips and it didnt idle up, IIRC that means theres no leak.

MaDMaX024

checking out the timing light deal tomorrow then i'm gonna hopefully finish porting my intake tomorrow and put it back on and get everything back together so all i need to do is get the fuel pressure down before anything else.
julio's FPR is 3-4psi lower than me.
his EGT readings are way high (1500 i think was his max) but he is running ludacrisly rich IIRC (370s, ZMAF and 43psi@idle) so the theory with his car is hes getting combustion in the manifold from all the leftover fuel and thats whats raising his EGT.
i pulled the EGR valve off and blocked the intake manifold hole..the car ran like it did with the EGR all connected and working except it sounded a bit interesting with the tube venting into the enginebay but now its all sealed up.
well see, i plan to improve my electrical grounds before i start it up again also just incase thats the problem (although doubtful that it is).
yes, the 2300rpm thing is very strange. thats why i blamed the MAF but it tested out fine in all respects. maybe if it still does it once back together i'll check MAF voltage when its hunting.