ZR8ED Posted September 3, 2005 Share Posted September 3, 2005 Hi uh.. I'm still at it with the Z. It runs pretty good... cold idle, the air fuel is around the 12-13's. The car warms up to full operating temp, and air fuels are around 14:1. IF it idles at 1200-1400rpm. Some times it idles there.. and sometimes More often than not, it idles at 900-1000rpm.. at which my air fuel ratio goes to 16-17:1 and the car idle lopes a bit, and my boost guage reads 10 inches of vacuum. (at my elevation, it should be in the 18 inch range) WTF???? Same on the highway... slow speeds on the highway that cause some engine loading... around the 10 inches of vacuum to almost 0 inches, the car will go lean.. I mean LEAN.. 16:1... Squeeze the throttle and bring on some boost, and the air fuels go below 12:1 depending on throttle.. WOT I get 11.4:1 I'm looking for some good info, on rpm/fuel pressure, timing and how they interact with eachother. I don't know whether to bump the fuel up a bit, or make sure the idle doesn't get under 1200... ie at full temp, set the idle a touch higher than it is now.. OR do I mess with more timing... I"m sure I'll check them all out, I'm just looking for some info on their effects on eachother, so I can cut down on my experimenting time.. I"m on my own this time. No local help... Other than that.. Temps are great, oil pressure is great, and car pulls like a freight train.. Thanks, Scott. Quote Link to comment Share on other sites More sharing options...
spork Posted September 3, 2005 Share Posted September 3, 2005 Just curious...I assume you're using some sort of wideband to determine this? Just wanting to make sure...by the way, can we have more info on your setup? Stock fuel computer, aftermarket management? The more info, the easier to help you. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 3, 2005 Author Share Posted September 3, 2005 Oh yea.. I have a very nice wideband setup.. spared no expense this time around...though I'm not using the data loging. Other stats VG30et SVO injectors. Mallory fuel pump Mallory FPR 3" exhaust downpipe and back.. Larger Throttle body. 60mm 2.5" in and out I/C Large Volvo i/c t3/t4 hybrid turbo. 5spd 3.7LSD 315's out back Custom burned ECU to match my turbo/injectors Jacobs ignition system/coil Just looking to get safely back to 15-17psi Currently set at a safe 10psi till I resolve some of these questions. Quote Link to comment Share on other sites More sharing options...
spork Posted September 3, 2005 Share Posted September 3, 2005 hos it always been like this since you installed the ecu, or is it something that developed afterwards? I'm just trying to narrow things down...by the way, who burned the ecu? Also, your right, your vaccum should be higher at idle. Are you running a stock air idle control valve? have you checked it per your FSM? You're car shouldn't be idling that high unless the engine is cold...or it thinks the engine is cold. If your car has a fairly agressive aftermarket cam, then you might need a higher idle, but it doesn't sound like thats the case for your car... Quote Link to comment Share on other sites More sharing options...
Guest ON3GO Posted September 4, 2005 Share Posted September 4, 2005 why not upgrade to a better intercooler??? mike Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 4, 2005 Author Share Posted September 4, 2005 I've had some troubles with the timing since I installed the ECU. A fellow member of this board did the burn, and ran it on his own car before I got it. The rest of the engine is pretty stock. Stock air idle idle control. It seems sometimes it will idle at 12-1400.. but when warm, it is idleing at about 900-1000rpm. It should technically idle at 700 since is has stock cams etc.. I watch the air fuel ratio, and when sitting at a light, the idle settles down to the 900-1000 rpm mark, the car idle lopes a bit, sounds like it wants to stall, and my vacuum reads about 10 inches, and the air fuels read high 16 into the low 17's (at which point the guage reading turns to just lights and no numbers) I'f I just touch the throttle slightly, and bring the rpms above 1200 rpm, the idle smooths right out, air fuel reads in the 14's, and vacuum is at normal (18 inches) I think I'll try and richen it up a few psi... that is if I can find my adapter for the fuel pressure guage. ( I don't have one mounted in the car/or under hood) Oh and Mike.. I try to only replace or upgrade when I break it... Its a long very expensive lesson about "while I'm at it" syndrome. I'm a recovering addict....I have to be careful. Scott. Quote Link to comment Share on other sites More sharing options...
Administrators SuperDan Posted September 5, 2005 Administrators Share Posted September 5, 2005 The symptoms you are describing allmost sound like you are having ignition missfires. Low vacuum and a false lean reading plus rough/low idle can all point to missfires. Can you log your AFR and review it to see if you are getting any spikes (like 20:1) in the afr? Just another opinon. Dan Quote Link to comment Share on other sites More sharing options...
datsunlover Posted September 6, 2005 Share Posted September 6, 2005 Maybe a silly thought, but I like to keep it simple stupi... you know. Have you pulled the throttle body apart and cleaned it really good? My truck has close to the same engine you're runing (VGsonmthingorother..) and before I had the 'constant high idle problem', it would do what you're describing.. Idle up to around 12-1400... sometimes stay, sometimes drop to 900... ect. I know you're ecu has be re-programed, but I think it could still be getting 'confused' by a strange reading from the TPS.. which it would base timing and fuel off wouldn't it? Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 8, 2005 Author Share Posted September 8, 2005 Well another update. Still no dyno session. That will have to wait till next week when I have another day off. Ok so here is where it stands now. I took the car for a 1hour drive to a club meet. I parked the car and let it idle. Fully warmed for sure... It is idling at 1400rpm. I hop out and adjust the idle to a nice 1000rpm. Idle is smooth, Air fuel ratio is in the high 14's low 15's, vaccum is in the normal range 18inches approx. I come out of the meeting 3hours later, and fire the car. It idles at about 1000rpm. smooth, same air fuel (15's) same vaccum. Cool. I drive the car home no problems. air fuels are in a good range all the way home. It got a bit lean when transitioning quickly to WOT, but then richened right up into the mid 11's (air fuel guage) Different speeds different throttle positions, I never saw anything higher than very low 15's. Most of the cruising was in the mid 13's. I pull off the highway near home.. and car idles like crap at 500-700rpm.. vacuum reads 10 inches, and air fuel reads 17's. It does this for the next three sets of lights that I stop at. The last 3 stop lights, everything is back to normal.. 1000 rpm, 14-15:1 air fuels and vacuum at 18 or so. I pull in the driveway and cool down the motor and pop the hood. I notice the idle is closer to 950, so I adjust it to 1000rpm dead on. Idle is still smooth, air fuels are good and so is vacuum. I think it is somthing other than my general tuning, since the condition can come and go.. Maybe i should swap in my spare air idle control? and clean every contact I can find on the throttle body... More to come.. Quote Link to comment Share on other sites More sharing options...
Sean 83ZXT Posted September 10, 2005 Share Posted September 10, 2005 You might also try cleaning the ECU connections. Quote Link to comment Share on other sites More sharing options...
Z-Gad Posted September 10, 2005 Share Posted September 10, 2005 Check for vacuum leaks at all connections, hoses and around your injector seals as well. They'll cause all kinds of odd idle/air/fuel issues. Quote Link to comment Share on other sites More sharing options...
Bernardd Posted September 10, 2005 Share Posted September 10, 2005 I had a sort of similar problem after changing out a headgasket. I went through ALL EFI connection, ecu, injectors, sensors etc... and sprayed them with contact cleaner. It's been two weeks and it's still ok. BTW that is tune was run on my car for an entire summer with no problems with either the timing or high idle. I don't use the idle control from the z31 at all. I adjust the throttle stop to the desired rpm and it's fine for me. Bernard Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 10, 2005 Author Share Posted September 10, 2005 Thanks Bernardd. I have a gauge on my fuel pressure regulator, and I noticed that it was set a bit lean (factory settings) It was adjusted a bit when my mechanic was messing with the timing and idle before. I have now tweaked the idle some more after taking it for a long drive. I upped the fuel pressure, and I don't get that higher air fuel ratio while driving now. It was still in the high 13's at partial throttle positions. I adjusted it a bit more, and had to adjust the idle again after increasing the fuel pressure. I need to go out for a long drive again. I'm running 30psi at idle now (vacuum line off and plugged) This is where the manual says it should be, and I will continue to adjust it from here. I'm going to put the boost back to where it was (15) and adjust the fuel as needed. I will likely have it dialed fairly close before I even get it on the dyno. But that is ok. It will save dyno time and $$ I'm watching for this low idle condition. it happened 2 times while driving in town. I didn't know I could remove the idle air bypass...I don't drive in the cold anyways...hmm... mabye I should just unplug it, and see if the low/rough idle stays always, or doesn't come back... More to report back with again...... Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 14, 2005 Author Share Posted September 14, 2005 This just gets better and better... MSnS is starting to look better and better. Ok. More update. More playing with idle, and fuel pressure. I think I have it running very good. I go out for a drive and yup, its running quite nicely. I stop by to look at a Z for sale, and when I come back to my Z, I start it, and it idles at 11:1 air fuel and 20 inches of vacuum. I drive the car home, and it is pegged at 11:1 air fuel, but the car is running ok. The only time the air fuels lean out, is when I shift and the bov goes off, or when I coast with my foot off the throttle. Other than that, idle, accel, WOT, it is pegged at 11:1. Great! just great...now what. I get home exhaust is stinking.. i pop the hood and start checking for vaccuum leaks, wires off etc. The car is idleing at 1000rpm..fairly smooth, and reading 11:1 air fuel. I wiggle the connector for the TPS, and the car starts to run like crap etc.. I check the air fuels...sitting at 12-13:1.. what? It is running leaner, but stumbling and idleing at 1100rpm approx. i pull the vaccuum line from the FPR, idle comes up and smooths out, air fuels in the 13:1 range. idleing at 1300. I plug it back in, and idle goes back to 1000, and 11:1 Looks like I may have some electrical gremlins plaguing my attempts to dial in the car... I'll let it cool down, and see if the problem goes away again. Let me cool down as well. Any ideas on prices to wire a MSnS for a VG30ET motor? This is getting rediculous. Quote Link to comment Share on other sites More sharing options...
Bernardd Posted September 14, 2005 Share Posted September 14, 2005 what happened to your timing during all of this? given it's habit of changing on you that may be the issue here. did you read datsunan's post about the loose rotor inside the distributor? do you have a spare working maf you can test? CAS? get rid of the idle control for now and adjust the throttle stop? remove all the connections under the hood (electrical) and spray them with contact cleaner. you should and probably have pressurized the intake piping to check for leaks correct? Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 15, 2005 Author Share Posted September 15, 2005 i actually have a complete running 88 300zxt I can use for parts. I have had zero problems with my I/C pipes etc for several years now. When it did leak, it was very obvious. The car idles very nice right now...even reading 11:1. air/fuel. kinda strange. The last few days the car has been running very strong and smooth. This sudden idle drop is appearing more and more like electrical. I'll get rid of the air idle control.. it always gave me troubles thinking way back... I ended up putting in a blockage in the pipe to reduce air flow...hmmm it just hit me as I typed this... I was being chased by the rain, but I managed to clean some of the connections up, once that I found the TPS connecter doing "wonky" things when I jiggled the connector... That is one other thing I didn't mention..I rained on the ride home..It was raining when I started to drive home......maybe something got wet?..hmmm My air fuel ratio harness is mounted on the frame rail, I wonder if it got wet, and its just the guage going "wonky"....hmmm Well I have time after work tonight..I'll get back at it...I only have a few more days till Zfest! Thanks, Scott. Quote Link to comment Share on other sites More sharing options...
BrandonsZ Posted September 15, 2005 Share Posted September 15, 2005 This may be in bad taste, but I love my carburator. Can a man love a carburator? I think so. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted September 15, 2005 Share Posted September 15, 2005 You may also want to check your EGR valve (if you have one). If it's sticking open sometimes, your idle will definitely go to hell. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted September 16, 2005 Author Share Posted September 16, 2005 Ok I checked the egr. unplugged it..car defineatly idled much much worse. Car is still idleing at 1000rpm and reading 11:1 today. 20 inches of vaccum and about 25psi of fuel with vacuum line attached. (near factory spec) I tried unplugging the o2 sensor (stock one) no effect unplugged the idle up solenoid.. no effect unplugged the idle bypass solenoid no effect. the car seems to idle nice and smooth. I pulled apart the dizzy.. rotor seemed a bit charred.. I cleaned up the connection points and rotor. this had a very minor effect, and air/fuel now sits at 11.3 - 11.6:1 air fuel when at idle small improvement. Timing is the same.. car is repsonsive with throttle at idle and driving.. no stumbling or hesitation... At idle standing back at the tailpipe closely...will make your eyes water..so I think the guage is working, and reading the rich condition correctly.. I'm running out of ideas. Cleaned and used dilectric grease on the o2, tps, egr, idle up, cold idle plugs. no change.... Can't see any leaks, temps are good, injectors look dry, hose clamps so far look tight... I tried to check the tps according to the manual looking for continuity between the top and bottom pins (vg's have 3 positions) I couldn't get any...that is assuming I did it correctly.. I'll be back with more info... This is getting old fast... Quote Link to comment Share on other sites More sharing options...
datsunlover Posted September 16, 2005 Share Posted September 16, 2005 Heck man, if you have a runing parts car to pick from, I'd just start switching out parts.. TPS, maf, ect.. Also, the ting I've noticed about VG engines is the condition AND quality of the cap/rotor is very important. Even though it lookes ok, it may be causing problems.. Quote Link to comment Share on other sites More sharing options...
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