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Old 04-29-2004, 01:43 PM   #1 (permalink)
ZUK
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possible cause of racing idle?

friend's 1986 Nissan extra-cab (720) 4 cylinder carbed (the one with the 8 spark plugs).....she goes to start it and idle is racing around 2200 or a little more. This is Arizona....it should have been around 1400 and then cooled down to an even 1000rpm. She's also burning gas at a faster rate(used a 1/4 tank driving it around this morning). It stays at 2200 all the time even after warm-up. I checked the linkage and there is slack in the throttle cable and nothing is binding. I did a "work around" to get the idle down to 1000....I turned the fast idle screw down all the way......I think the computer still thinks the engine is cold so there is some sort of fuel enrichment is still going on. Anybody ever have this happen? Not just a crimped cable....perhaps a vac line or temp switch? I don't have access to a FSM. Now if someone has access to an FSM....and can scan in the temperature switch location, that would help.........I bet one of those vac lines going to the carb causes fuel enrichment......what do ya think?
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Old 04-29-2004, 02:29 PM   #2 (permalink)
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there is a "wax pellet" in the throttle body that goes bad. My truck does that...you have to replace the throttle body, so I haven't messed with it. After it warms up it idles normal. The wax pellet heats up when the truck gets warm or something like that...I don't remember exactly.
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Old 04-29-2004, 02:57 PM   #3 (permalink)
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Yeah the wax pelet thingambob sounds right. Even my 98 has one, but it is somewhat rebuildable as the O-ring failed on it and I replaced justed he O-ring.
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Old 04-29-2004, 03:21 PM   #4 (permalink)
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Quote:
Originally Posted by bignissan
there is a "wax pellet" in the throttle body that goes bad. My truck does that...you have to replace the throttle body, so I haven't messed with it. After it warms up it idles normal. The wax pellet heats up when the truck gets warm or something like that...I don't remember exactly.
You guys sure that sounds right? The idle stays over 2000 even after an hour of run time......yesterday, everything was fine(idle was around 1000)....this just suddenly occurred today.
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Last edited by ZUK; 04-29-2004 at 03:25 PM.
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Old 04-29-2004, 04:58 PM   #5 (permalink)
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You sure it is warming up completely? My old truck acted like that when the thermostat went bad. Another cause could be the linkage for the fast idle cam is binding on the carburetor. Not sure how the if/how the old Z24 has that set up but my old Mitsu required adjustment/lurbication once in a while.
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Old 04-29-2004, 05:47 PM   #6 (permalink)
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I also had a Z24, Chris, that wouldn't idle down because it never heated up, bad thermostat. It had the TBI injection and used the wax pelet.

WHen it's running just look at the throttle linkage and see if it's against the stop.. if not then push it back or see what's holding it up..
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Old 04-29-2004, 06:08 PM   #7 (permalink)
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yeah, it's possible it's not warming up completely either....worth a shot to check though
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Old 04-29-2004, 08:40 PM   #8 (permalink)
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Tps?
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Old 04-29-2004, 10:26 PM   #9 (permalink)
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didn't think about that..that is a possibility as well
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Old 04-30-2004, 11:17 AM   #10 (permalink)
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It's carbed...2 barrel.....no TPS. There's quite a bit of mechanical linkage. I may just have to dis-able the high idle circuit altogether.....no one has an 85~86 FSM handy?
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Old 04-30-2004, 11:20 AM   #11 (permalink)
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Quote:
Originally Posted by bignissan
there is a "wax pellet" in the throttle body that goes bad. ............................

B
bignissan---If that statement is accurate about the throttle Body part then I don't think it applies to this carbed unit.
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