driftinpinoy23 Posted April 1, 2007 Share Posted April 1, 2007 hey guys my 280z has a lack of power and makes a popping noise only on rpms lower than 2000. So far we've changed the spark plugs, plug wires and sanded the contacts inside the distrubtor because of corrosion. Also im not sure if this is a factor but we've put 87 octane and just switched back to 91 at 50%. Thanks in advance for your help guys. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted April 2, 2007 Share Posted April 2, 2007 Try to provide more information about your car. Does it have the stock motor? If it's a 280 it has electronic ignition. Sanding the contacts inside the distributor is a no-no. What do you mean lack of power, discribe? octane of fuel shouldn't make a big differance. Quote Link to comment Share on other sites More sharing options...
driftinpinoy23 Posted April 2, 2007 Author Share Posted April 2, 2007 its a stock l28. and when your stepping on the accelerator, you dont feel a response until a few seconds. and it starts to misfire. until you are at higher rpms than about 2-3k Quote Link to comment Share on other sites More sharing options...
datsunlover Posted April 3, 2007 Share Posted April 3, 2007 I'm goint to guess (with the limited info I have..) the TVS (throttle valve switch) is a possible cause. It's NOT a 'sensor' , but more simply two switches, one for part throttle, and another at 50% or more..(or something like that, I'd have to look in the fsm) and it could be the first switch is not making good contact, causing the ecu to go "AAHHHHHGGG!!!!!!!" and backfire as it messes with fuel and ignition timing to try and cope with a bad signal. The AFM could also be causing simmilar issues, or bad reading from the AFM due to a cracked boot (sucks in extra air that the AFM doesn't see, but it's there and changes air fuel ratio, ect.)between the AFM and throttle body. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted April 3, 2007 Share Posted April 3, 2007 datsunlover: I think your guess is a good one. The throttle position switch is a real possibility. Driftinpinoy: Pop the cover off it. Adjust so that the first set of contacts opens just off idle and the second makes contact (as datsunlover said) somewhere above half throttle. Make sure at fully closed throttle the first set is seated, and most important that both sets aren't closed at once. Looking for air leaks in the boots is another great piece of advice although the symtoms sound more like TPS. Pull the pleats in the boots apart and look for tears. Quote Link to comment Share on other sites More sharing options...
280zwitha383 Posted April 5, 2007 Share Posted April 5, 2007 How exactly do you pop the cover off? It looks to me like the connector wants to come off with it if you were to force it off. Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted April 5, 2007 Share Posted April 5, 2007 How exactly do you pop the cover off? The cover on the throttle position sensor? It has little plastic tabs and just snaps off. Be gentle, it's old and brittle and the tabs could break off. Pry at one side, then the other. It should come off with nothing more then your fingers. It looks to me like the connector wants to come off with it if you were to force it off. I just went out and checked on mine and the wire connector definitly doesn't have to be removed. Mine is a 77. It does look like it might be part of the cover, but it isn't. After coming on and off so many times, mine is kind of loose and I use a zip tie wrapped around it to hold it in place. Quote Link to comment Share on other sites More sharing options...
280zwitha383 Posted April 6, 2007 Share Posted April 6, 2007 Well I was messing with this guy last night and it was dark so I never got the cover off. However, with a ohmmeter you can just as easily check for continuity. First, the two pins facing the cab of the car should have continuity at no throttle. It should break continuity as soon as you barely touch the throttle. Then, as stated, at about 1/2 throttle the second two pins (or facing the front bumper) should have continuity. So really the computer knows no throttle, some throttle and more than 1/2 throttle. Right? Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted April 6, 2007 Share Posted April 6, 2007 Correct-a-mundo 280zwitha383. It's not a true throttle position sensor. It's a two contact point switch. Using an ohm meter as you described confirms it's working as advertised, so long as both sets don't have continuity at once. The first set tells the computer he is idling, and should open (break continuity), like you said, just off idle. The second set add enrichment (adds more fuel) for higher RPM operation. About 3/4 open would be a good guess if you don't have a wide band or something. Are you working on the original poster's car? It's a stock FI setup? Just wondering, because of your user name. 280 with a 383. Where's all your stock FI stuff, wanna sell it? Check my signature. Quote Link to comment Share on other sites More sharing options...
naviathan Posted April 6, 2007 Share Posted April 6, 2007 Sounds like it's running rich to me. Check fuel pressure, change the cap and rotor button, pull your plugs and see what color they are, pull the fuel rail and turn the key to kick on the pump (don't start), look for leaking injectors or cold start valve. Quote Link to comment Share on other sites More sharing options...
280zwitha383 Posted April 7, 2007 Share Posted April 7, 2007 I have a mostly stock 280ZX and then the 383 280ZX. I bumped the timing up about 16 degrees from about 2 degrees to 18 and noticed a nice little umph. My vacuum advance doesn't work so I figured it could use a little more timing than stock (which should have been 8 degrees I think). I also used the second setting on the timing gear (cam gear) because the chain was stretched. I think I've fixed my problem of bogging and hesitating at below 2k rpm's. There for a while I was popping at lower rpms and I thought I was just running lean but my plugs looked good so I started looking for other stuff. I remember messing with the tps during all of this and trying to take the whole thing off. I messed with the positioning of it too to see if it would change anything (I didn't know where it should be so I thought I put it back to where it originally was and apparently I did). Anyway, maybe some of the things I mentioned will help give you an idea of what to look for. Quote Link to comment Share on other sites More sharing options...
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