Guest illushynZXT Posted May 15, 2002 Share Posted May 15, 2002 Hey peeps. I've got a rather annoying problem with my 82ZXT. Even the Nissan Z techs I've consulted are perplexed .. hopefully someone here might be able to give me a possible solution. http://zcar.com/forums/read.php?f=1&i=276015&t=276015 I would really appreciate any/all responses or thoughts about this. -il82 Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted May 15, 2002 Share Posted May 15, 2002 You're wrong about one thing...It COULD be the AFM...why? I'll tell you. Even though you can rev your engine up to 5K+ at an idle doesn't mean that your AFM flapper door is opening all the way. In order to get the door to open all the way the engine has to have a certain amount of load on it (much like the engine has to be loaded to spool the turbo - ever notice you can spool a big turbo quicker in 3rd gear than in 1st gear? That's why you check your boost in 3rd gear, and not in 1st gear...) I'd check that. Also, ohm check your TPS. It could be perfectly dry but still be bad. Let us know what you find with those two items, then we can go further into it. Quote Link to comment Share on other sites More sharing options...
Sean 83ZXT Posted May 15, 2002 Share Posted May 15, 2002 Many people who own turbo ZX's have similar problems. The fix is to generally unplug (while the car is off) the 3 harness plugs going to the main ECU under the drivers side kick panel. Once they're off drown them liberally with electrical contact cleaner. It is designed to evaporate so let it dry for a few seconds and put the plugs back in. Mine did the same thing for a while and that fixed it. Over time you'll have to do it every so often so when I had a spare car to drive I also took the ECU out and gave it a major contact cleaning. I used a small nail file to clean off debris, but an emery cloth should also work fine. Let me know how it turns out. I'd try this first because it's a very cheap thing to try. Quote Link to comment Share on other sites More sharing options...
Guest illushynZXT Posted May 15, 2002 Share Posted May 15, 2002 Thats something that I dont understand then.. If the engine revs up to 5000, logically that flapper door should open the same amount (at least in the beginning) as it does at 5000 under load. So even for a moment, the flapper would be in the same spot as it is when it dies. Either under load or not, as long as my car is going over 20mph, it will not rev past 2250. Considering 20mph is like a key figure, I also dont see how the AFM could be involved. If I am smoking crack here.. let me know. This is driving me nuts. -il82 Quote Link to comment Share on other sites More sharing options...
Guest illushynZXT Posted May 15, 2002 Share Posted May 15, 2002 Well, I took the ECU out of the car, disassembled it, reassembled it, and put it back in the car. There was no corrosion at all on or around the ECU. Still no go. This kinda crap is making me wish I had the couple thousand dollars to drop a TEC2 into it. Least that way I could know for sure what was wrong... *shrugs* Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted May 15, 2002 Share Posted May 15, 2002 The flapper will open more under load than not. The engine is consuming more air under load (producing power) than when you are not moving the car, so you will get more deflection as more air is drawn - it is not particularly RPM dependent. Still sounds like a shorted idle TPS contact to me, either at the TPS or in the ECU. The reason you can run the RPM past 2000 RPM is the engine is not loaded and is not consuming the fuel - I believe the TPS at idle will limit the fuel to a small amount, and this is enough to propel an unloaded engine to any RPM, but under load - cough! pop! sounds lean and no power. The Z31 folks will tell you AFM, but the flapper ECUs are different, and may not exhibit the symptoms, but I don't know that. Disconect the TPS connector and leave it off. You can also try measuring for continuity through the open connector. Quote Link to comment Share on other sites More sharing options...
Guest Aaron Posted May 15, 2002 Share Posted May 15, 2002 my current 82ZXT does the exact same thing, and it is the AFM. I am not repairing mine because I am planning a v8, so I refuse to waste that money on something I won't use long. I had an 81ZXT in High School that acted similarly, and it had a bad connection in the wiring harness just as it plugged in to the compter. I fixed it by leaving the kick panel off and reaching down with my left hand and wiggling the wires whenever it acted up. Quote Link to comment Share on other sites More sharing options...
Guest illushynZXT Posted May 16, 2002 Share Posted May 16, 2002 The AFM and all related electronics pass all tests. Still no fix. The TPS is operating perfectly, as is the AFM. The only problem is the 20mph thing.. as even under no load, if the car is over 20, it still does it. I'm losing my mind... -il82 Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted May 16, 2002 Share Posted May 16, 2002 So....how about the rubber boot between the AFM and the turbo? I had a big leak there and it ran like crap, but it wouldn't idle either. Your issue can only be caused by one or two things (already mentioned), so swap an ECU and see if that fixes it, as the TPS signal could be messed up inside the box. Quote Link to comment Share on other sites More sharing options...
Tony240ZT Posted May 16, 2002 Share Posted May 16, 2002 Fuel pressure could possibly be low enough to make a problem like this. A dying fuel pump, stuffed line, or stuffed fuel filter could make it so not enough fuel could flow. Might be worth checking to see if you have enough presure. The 2250 rpm limit sounds so familiar. Having the TPS foul does exactly the same thing. Try running the car without it plugged in. The fact that you can rev it without in gear suggests it's not related though. I swear cars should have air/fuel ratio gauges installed in them from the factory, you can learn a lot from them. And yes, the AFM could be the problem. Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted May 17, 2002 Share Posted May 17, 2002 If you're testing the electronics off of the car, test them in the car at the ECU. Sometimes doing pin checks at the ECU will help you determine if you have a harness or connection problem. The only way you're going to put a significant amount of load on the engine at a rest is if you have an automatic and can powerbrake it (or if you have a studderbox, but I can't recommend a stutterbox for diagnosing this kind of problem) Quote Link to comment Share on other sites More sharing options...
Sean 83ZXT Posted May 17, 2002 Share Posted May 17, 2002 If ya check out zcar.com, he found the problem. I guess the speedometer sensor was bad and when he unglugged the speedo it worked fine. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 17, 2002 Share Posted May 17, 2002 You say the AFM has passed all tests. Did you disassemble it and look for warps or bends in the actual door itself? If the engine has ever backfired , etc. the door can get bent and act normal with a few exceptions. Also have you put the car on a scope? What kind of voltage readings, etc. are you getting from the computer? My 2 cents... Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted May 17, 2002 Share Posted May 17, 2002 Hey did you check the exhaust manifold for leaks?? The same thing happened on my Volvo 240 Turbo and it confused everbody I talked to until I heard a slight hissing sound. It ended up a hairline crack when the castiron was cold but when the exhaust manifold warmed up the crack got bigger. With a exhaust leak before the turbo, the turbo cannot build pressure to turn the turbine and will not be able to boost good. And the engine will not rev past a point. It sucked that my top speed was 35 on the highway floored in 5th gear Hope this helps, Mark Quote Link to comment Share on other sites More sharing options...
Sean 83ZXT Posted May 17, 2002 Share Posted May 17, 2002 Like I said if the guy posted that he found the problem. He posted on zcar.com. Quote Link to comment Share on other sites More sharing options...
Guest illushynZXT Posted May 18, 2002 Share Posted May 18, 2002 No.. not really found the problem. I havent isolated it yet, but it appears to be a transient short somewhere in the instrument cluster thats causing it. Least when I jiggle different things here and there in the cluster it comes and goes. I have more details of it on zcar. "My soap opera continues" Geez.. -il82 Quote Link to comment Share on other sites More sharing options...
Guest illushynZXT Posted May 19, 2002 Share Posted May 19, 2002 Well, I have no idea what was causing it, but its obviously a transient gremlin. The car is running fine now.. and survived a 328mi trip tonight without any problems. I dunno.. but since its working now, I guess I cant complain about anything. Thanks for the info guys. I've got an FSM for this model on the way in case I have to try and track this down again. -il82 Quote Link to comment Share on other sites More sharing options...
Guest MHarpham Posted May 2, 2006 Share Posted May 2, 2006 Darn I was hoping to find an answer. My car does the same thing and I have had no luck fixing it yet. Going to try some stuff after work.. please let me know if you come up with anything new. Mattharpham@hotmail.com 78 280Z 2+2 Quote Link to comment Share on other sites More sharing options...
Guest MHarpham Posted May 13, 2006 Share Posted May 13, 2006 Mine was the AFM not functioning properly. Mine tps is also garbage but that wasnt what was causing my car not to go above 2k under load. Quote Link to comment Share on other sites More sharing options...
AK-Z Posted May 13, 2006 Share Posted May 13, 2006 Old thread. Quote Link to comment Share on other sites More sharing options...
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