evildky Posted April 25, 2004 Share Posted April 25, 2004 ok, I have replaced just about everything, I have replaced, the ECU, distributor, TPS, AFM it is still rtefusing to boost, just as manifold pressure reached zero, it just kinda dies, for a split second there is just nothing, then it'll surge to maybe 2 lbs just to die back to zero and do it again, I have run out of stuff to replace, I even tried disconnecting the vac/boost line going to my wastegate, still won't boost !? I have tightened every hose on the car I can detect no leaks, I am about to try getting a junkyard toubo and try replacing that, any ideas ? help me out please !? I have found a coupla of similar post's but neither of which seems to heve been resolved, Help ! Quote Link to comment Share on other sites More sharing options...
lifegrddude Posted April 25, 2004 Share Posted April 25, 2004 You probably have a faulty wastegate or either that, the little dash pot to the wastegate is stuck open. Look on the turbo to where the rod for your wastegate attaches. See if it in the closed position and not open. John 82ZXT Quote Link to comment Share on other sites More sharing options...
evildky Posted April 25, 2004 Author Share Posted April 25, 2004 well, the wastegate bracket was a little bent, I corrected it and no change, I wired the wastgate open and it has the same problem but now at much lower rpm, now it cuts out at about 15-10psi vacume I tripped the actuator with compredded air, it seems to pop out and return fine, but the wastgate arm in the position of about 3/16 out and being completely shut seemed to have the same result, car dies at around zero manifold pressure so I have a bad turbo or is it the wastegate ? could it be that the wastegate is just not sealing all the way up ? and maybe it needs a new flap? or is the tubo simply not generating enough boost? Quote Link to comment Share on other sites More sharing options...
v8dats Posted April 26, 2004 Share Posted April 26, 2004 are u putting the engine under a load? or are u just free revving it ? cause if youre just sitting there revving it wont make any boost untill u get to driving. i had a similiar problem with mine and i replaced the tps and it fixed it how? i dont know i guess it was majic Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 26, 2004 Share Posted April 26, 2004 doesn't make sense to be a bad turbo. Even if the turbo just completely froze up and couldnt spin, it would only become just a big restriction in the intake flow and exhaust flow, but technically your car would still drive okay, like it had suddenly become an N/A car. It wouldn't die above 0hg, it just wouldn't go any higher than that. I can't think of any other way a turbo could fail to cause this problem. Most common turbo failure is bearing or seal failure and burning lots of oil. I'm still betting on electrical on this one dude... if you replaced everything I'd put my money on a short or break somewhere in the wiring harness. Again, I had the EXACT same symptoms when I got water in my AFM connection, which in effect caused a short between two of the AFM's contacts. I know you cleaned all the connections (which you said did seem to help for a short while?) so it may just be in the wiring itself. You can go about testing all your wiring connections yourself or I think some shops probably have a way of doing it quickly, I'm not sure. I've had two wiring harnesses go bad like this on me and cause the same hair pulling as I tried desperately to replace and diagnose and fix everything. One of these harnesses I had bought from a friend and it looked damn near brand new. Two months later the car started running super rich and crappy... after trying lots of things I took it to an electrical place and sure enough there was a short, I think it was either in the TPS or the head temp sensor wiring. I'd think of replacing the harness before spending a fortune on replacing the turbo..... at least get a voltmeter and try to start checking for shorts. Quote Link to comment Share on other sites More sharing options...
evildky Posted April 26, 2004 Author Share Posted April 26, 2004 ok real quick, v8dats, yes it's under load, I can free rev all day with no issues at all I removed the down pipe and checked the internals, the turbo seems fine, no resistance, no free play at all on the exhaust side, just a little barely detectible movement on the intake side (nowhere near enough to rub) well if I could find another turbo harness I'd switch it, problem is these are rarebirds here in the rust belt, they all rusted in half and had thier remains crushed years ago, took me forever to find a doner the thing that troubles me about the turbo is that with the wastegate cracked and with the wastegate corrected the car behaved in the same manor I can totally see it being an electrical problem, I can be in second gear, slowly accelerating get up to around zero and it's just a nothing, I'l be at around 2500rpm and it's just dead silence, the tach holds position, there is no exhaust noise for that moment no anything, no engine braking that you'd expect with a dead car just nothing, it's as if someone hit the pause button anyone know where I can pick up another harness cheap? replacing all these parts is getting expensive! Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 26, 2004 Share Posted April 26, 2004 If picking up a harnes proves troublesome, try to track down the short/break or get an electrical place to look for it. If it's just one wire screwing up you can probably just replace the bad section or the bad wire in question w/o replacing the whole harness. Since there are only so many things that could be causing this problem, electrically, you shouldn't have to spend too long looking. I'd start with the AFM wiring, for sure. OH I almost forgot one other really important thing. Track down all your ground wires (I believe there are five) and be sure they are clean, and that the surfaces they are grounded to are clean. If you dont already have one, get a thick ground strap from your battery negative to the chassis. Bad grounds can cause lots of funky problems as well. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted April 26, 2004 Share Posted April 26, 2004 I don't buy an electrical issue keeping the turbo from spooling. What you need to do first is verify the valve on the swing valve assembly is still there, and covering the hole in the turbine housing. Sometimes they fall off, and it won't make boost. Then make sure the swing valve is working, ie the valve actually covers the hole completely, and that the motion of it is proper. Then make sure the wastegate actuator rod is putting tension on the swing valve when its all connected. Check the vacuum lines going to the WG actuator, and make sure none are cracked. You may want to bend the actuator bracket buy pushing up towards the firewall, which will add pressure on the WG actuator, and allow you to make more boost. Be careful though, this is like brylcreem, a little bit goes a LONG way. Finally what are you using for a boost guage? Make sure its a good one. Then make sure the dumb little pressure relief valve sitting on top of the intake is not popped open, or remove it and replace it will a plug. Quote Link to comment Share on other sites More sharing options...
Pyro Posted April 26, 2004 Share Posted April 26, 2004 Sounds like a bad flapper. Stuck open or fell off. You could also check the if the intake blades spin easily by pulling the intake tube off the turbo and spinning the blades manually (with the car off). You should pull off the down pipe and wastegate and make sure the exhaust blades are still there. And check the flapper while you are at it. Turbo boost is pure mechanical. Nothing electronic will stop it from boosting unless you have a bad electonic boost controller. And stock 280zx turbo's don't have electronic boost controller. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 27, 2004 Share Posted April 27, 2004 I don't buy an electrical issue keeping the turbo from spooling. But it doesn't sound like his turbo isn't spooling. It sounds like once boost becomes present in his intake manifold, the ECU is flipping out, either cutting fuel or timing or something like that. Even if the turbo wasn't spooling, he should still be able to floor the throttle and not have the symptoms he's having... I would figure that the motor would just behave like an N/A motor, with a restriction in the intake and exhaust (very low power and poor throttle response, but not the stuff he's experiencing). Again, when I had gotten some water into my airflow meter connector, my car did the EXACT same thing (I dont know why it seems you guys dont believe me when I say this). The car ran perfectly fine just cruising. And I could bring the throttle up and watch the boost gauge... as long as I stayed in vacuum everything would be fine. But the MOMENT the boost gauge needle crossed over from vacuum to boost, the car would start to bog and jerk and buck and stumble and pop. I limped it to a gas station, found out that there was water on the AFM connection, cleaned it off and afterwards the car ran perfect again. From evildky's description it sounds like EXACTLY the same thing. I know he's already checked and cleaned the connections, so my next suspicion would be a fault in the wiring harness itself, a short somewhere, which is essentially what I had with water on my connections. Quote Link to comment Share on other sites More sharing options...
Jersey Posted April 27, 2004 Share Posted April 27, 2004 Figure this out Evil? If i were to start tracing your problem, i'd go in the direction of LJ's advice. Not that eletrical couldn't or isn't the problem, 525 knows allllll about that department but it just seems as positive manifold pressure is created, it's just leaking out somewhere. What's attached to your intake manifold? Anything that could have taken a dump? Like the POS POV as LJ mentioned? Keep us posted... like to know what you found. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 27, 2004 Share Posted April 27, 2004 But boost leaks don't come on so SUDDENLY like that. Also the surging and such that he is describing doesn't match up with a boost leak. With a boost leak it's just a big bog and you should see black smoke coming from the exhaust as you run suddenly very rich. Or really you should just notice a gradual loss of power and you can just HEAR the motor starting to run too rich (sounds like it's gargling, or, and I'm not trying to be funny, but like it just got a bad case of gas). You will almost invariably catch of wiff of fuel smell as well. I accidentaly created a pretty big boost leak myself when I installed my BOV, left it vented, and didn't hook it up to a vaccum/boost reference. As I would come on boost the BOV would just be forced open, the car would gradually lose power as I revved it up, and boost was erratic, but it did build boost (never seen a boost leak that just would not allow ANY boost at all), and it started to smoke black puffs... His symptoms don't seem to match up with that at all. Quote Link to comment Share on other sites More sharing options...
Jersey Posted April 27, 2004 Share Posted April 27, 2004 Okedoke. Evil, are you running the J-pipe or intercooled? BOV installed? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted April 27, 2004 Share Posted April 27, 2004 I just wanted to say something regarding electrical causes for the boost issue. When I was running a factory 280ZX EFI, I had an issue come where the car would run fine under vacuum, but as soon as the manifold went positive pressure, it would bog out and not make boost. But if I slowly crept up on boost, not pressing the accelerator very much, I eventually could make a bit of boost. The problem I eventually discovered, after swapping my whole EFI with the Z31 not solving the problem, was bad plug wires. The engine would fire fine until load was applied, then the weak wires would not fire through the mixture, and voila! No boost possible. That's one scenario where an electrical problem will not allow boost, more or less. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 27, 2004 Share Posted April 27, 2004 Though my problem was definately not plug wires (just installed brand new NGK wires a couple mos ago), when you mentioned that it did remind me, that was another part of the symptoms as well. I could get into boost if I 'crept into it' adding throttle very slowly, but eventually at some boost point (seemed to be around 5psi) it would still start to bog. Quote Link to comment Share on other sites More sharing options...
evildky Posted April 27, 2004 Author Share Posted April 27, 2004 the turbo seems to check out, I pulled the downpipe and the intake tube, all the blades seem to be in good working order, there is no play at all on the exhaust side, the intake side has a barely detectable amout of movement, the wastegate actuator seems to work when I blow compressed air through it, it pops open the closes, the bracket seems to have been bent a tough, and the wastegate door was not quite closes, I prolly bent it working on it, the disk on the inside of the turbo that covers the wastegate hole seems to be fine, the swingarm the moves it seems to be fine, I am not burning aly oil ot making any smoke, seems pretty tighht for a junkyard motor the oil hovever does seem to smell of gas(not real strong, just a bit), I was thinking perhaps when it bogs and will not boost that the spark is cutting off for some reason, allowing unburnt gas to seep past the rings, my plugs look fine, no fouling or anything like that what else could cause this, the electrical short seems the most likely solution, but seems quite dificult to diagnose, I wish I could locate another harness, SDS is sounding better all the time but wiring up the optical dist is a bit daunting, and then SDS is not a cheap solution and I am already broke from replacing everything else Quote Link to comment Share on other sites More sharing options...
evildky Posted April 27, 2004 Author Share Posted April 27, 2004 and I am still running the jpipe, and the pressure relief valve on the manifold seems to seal just fine, remember that the problem occours at zero manifold pressure, actually now it seems to show up before I hit zero and the plug wires are Nissan Motorsport plugs about 6 months old and have got aybe 500 miles on them Quote Link to comment Share on other sites More sharing options...
Sean73 Posted April 27, 2004 Share Posted April 27, 2004 You said that you wired the wastegate open, but I don't see any reason for that test, since you'll never get boost that way. Wire the wastegate closed and go for a very careful ride while closely monitoring boost. I recently had a bad wastegate actuator on my rebuilt turbo. It would boost to 6 psi, then drop into a vacuum immediately. I did a test with compressed air, and found that the actuator was not responsive and very sticky. I trashed it and installed a oem nissan actuator, and now I boost fine. Also, once the actuator arm is bent, I think you're in for a world of problems. The behaviour of the actuator is very sensitve to the tension on that actuator arm. If anything is out of alignment, loose, or too tight, you'll get unpredictable response. Sean 73 240Z, L28ET, T3/T04E, NPR IC, 84 ECCS Quote Link to comment Share on other sites More sharing options...
evildky Posted April 27, 2004 Author Share Posted April 27, 2004 I am geting no boost at all, none! also the wastegate actuator arm is fine it's the bracket that was a little bent, prolly from me wrenching on the car, and I have wired the wastegate closed same effect, you can hear it winding but it will not boost, it gets a bit short of zero pressure like maybe 5hg vac and it just kinda dies for a minute Quote Link to comment Share on other sites More sharing options...
Pyro Posted April 27, 2004 Share Posted April 27, 2004 It sounds more and more like the flapper in the waste gate. The flapper closes off the exhaust port in the turbo and makes the exhaust spin the turbine. If the flapper is gone then the exhaust will not spin up the turbine. So, if this is the problem then any external and wiring on the outside of the turbo will not do anything. I think you should remove the down pipe then remove the waste gate assembly and have a look. But first check if all your rubber hoses on the turbo outout are in good shape. Boost can also be lost at those connections. Quote Link to comment Share on other sites More sharing options...
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