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Discussion Starter #1
i have a '94 sierra/samurai with the stock 1.3L engine... anyway tonight i was out driving: it started fine, and was running fine. stopped at traffic lights and idled fine. five minutes later i was home, and once i stopped the idle speed was fluctuating between 200-500 rpm! the engine wasnt hot or cold, it was well within proper range. i took it back for another drive immediately, theres no power loss and it runs fine, but as soon as its stopped, its back to odd idling!...
anyone have any ideas as to what might be causing this?
 

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does it only happen at night when the lights are on? It could be the alternator going bad or it could be your idle compensator. When you run devices that put a load on the engine, like the Headlights, or the ac, or power steering, the idle compensator bumps up the idle so that it doesnt stall out under load. If the idle compensator is getting a faulty signal or is dammaged it could cause erratic behavior of the enging at idle.
 

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Discussion Starter #3
heater and lights were both on, but it made no difference when i turned them off... but i'l try it longer than a few seconds today...
 

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could be a dirty ground or connection that is only going to act up on you when when it's damp with condensation. If it's your idle speed control then it only comes on when the engine is at normal operating temperature.
 

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Discussion Starter #6
ahh... it was raining at the time. goin away for 3 days so cant look into it til after that...
 

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Discussion Starter #7
rather than starting a new post, i figured i'd just go off this one again. its now doing the opposite by idling high... runs fine, but when stopped at traffic lights, it idles anywhere between 1200-1700rpm... however if u ram the throttle to make it jump to about 4k, it drops straight back to normal. next set of lights its idling high again, but same solution works again... anyone got any ideas as to what the problem could be?...

dont know if this has anything to do with it, but last sunday i went through mud that covered the sidesteps (it has 2" lift), although the problem didnt start til tuesday...
 

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Take the hat off the carb and clean the linkages and springs. It sounds like the idle cam might be catching. It should kick down automatically but if it's gummed up or the plunger isn't functioning right it will prevent it from releasing whithout kicking the throttle open. Also check to make sure you didn't blow a vacuum line off. I do that every once in a while when I'm runing it hard. If the throttle body hiccups, it can blow a vaccum line off of its port, especially if the hoses are getting old.
 

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Discussion Starter #9
just had a quick look... i think it could be the spring that pulls the throttle cable back when your foots taken off the pedal, the one thats just behind the carb... it doesnt seem to want to pull back properly, had a play with it by revving it, waiting for it to idle high, then help the spring by pulling it manually.

will any spring work for this, or do i have to get one exactly like this particular spring?
 

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check to make sure that there isn't an arm or a lever loose that releases a catch on that return spring. I've not yet heard of a carb spring going bad but I guesse it could happen. I don't know what you would use other than a stock spring from a busted carb... is the spring just not strong enough? Maybe the return mechanism is too stiff rather than the spring being too weak?
 

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Discussion Starter #11
aaaah now its idling too low to the point of stalling every bludy set of lights i stop at... mechanic suggested i try reversing the 2nd and 3rd spark plug leads then rev it a few times, then switch it back... just to try and backfire through the carb, clean the idle jets. tried that, made no difference...
problem is sometimes it idles fine, sometimes it idles too low. i finally worked out when it does what... if im just doing comfortable cruising through town, meaning accelerator only on lightly, then lift it and put the clutch in, it stalls. if i have the foot flat (any gear, doesnt matter) then lift it and push the clutch in, it idles fine... so only after light accelerating it stalls... does this come back to the idle cam catching?



nd yea, the return spring is just a little loose...
 

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well it shouldn't ever be loose. There should always be a slight tension on it. Have you adjusted the cable or maybe removed the bump stop under the accelerator pedal? If the cable pulls too far, you can bend the arms in the linkage and brackets behind the carb.

Also check your hot idle plunger to make sure it's able to hold a vacuum. It pulls it's vacuum from the manifold through the front VSV actuator. If there's a vaccum leak anywhere along there or if the diaphragm on the plunger is leaking then you might not be able to get enough draw on it to idle up.

Hopefully Ack can step in here, this is more his area of expertise.
 

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Discussion Starter #13
i havent adjusted anything, just has a little bit of slack... its really driving me insane not being able to stop at traffic lights... im thinkin i should just get the carb completely rebuilt...
 

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If you didn't adjust anything and it just started behaving this way all of a sudden, then something must have broken, bent, or popped loose.

It's usually more cost efective to get a rebuilt unit. They're about $250 US. after the core exchange.
 

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Discussion Starter #15
dont know if they have anywhere in aus that does that... i was quoted $400 to rebuild this one by the only well known mechanics that service carburetors within about 200km (~150miles) but i have since found another guy that does it, still yet to get a cost.

update as well: its running fine again. slightly more shaky but stays on at lights at least... was fine after i did that thing where i switched the spark plug leads around nd revved it (the car didnt like that, shook nd spluttered nd carried on, but even an idiot like me can expect that) then i took it and went on the highway in 4th gear for about a minute at 4500rpm... all good, at least for now.

oh, and the mechanic just sprayed some wd40 or something like that on the spring and around that little quarter circle thingy, which fixed that... made me feel like an idiot for not thinking of it :p
 

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Sounds like some routine maintenance needs to be preformed. If you haven't done so get some carurator cleaner and spray the carb down real good. You should use the whole can.

Spray some of that cleaner on the linkage and the exposed cable ends.

Afterwards you will want to change the plugs. (All of the crap that you break loose will be detonating in the cylinders so the plugs take a beating.

If you want to add some fuel additive to the next few tanks of fuel that sure won't hurt.

If your carb spring is still a little loose cut a small amount of it off with a pair of sidecut pliers. Then gently strech it out and relace it.

I would also replace the spark plug wires, the distributor cap, and the air cleaner.

Based on your desription I would think that your little Zuki should run and breath alittle easier for you down the road and and at the next stop.

Tux... ;)
 

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Take the hat off the carb and clean the linkages and springs. It sounds like the idle cam might be catching. It should kick down automatically but if it's gummed up or the plunger isn't functioning right it will prevent it from releasing whithout kicking the throttle open....
I thought you already did this.... That's what ya get for ignoring my advice.. ;)

I'm glad it's running smoother now. If you ever do get the carb rebuilt, don't send it to an automobile carb shop. They always look at like it's some kind of chinese puzzle box and tell you it will cost more to rebuild it than to buy a new vehicle. A motorcycle shop will probably be more adept at working on one of these little guys, but a place that specializes in zukes will be the best place to go. Even with shipping, I would think getting a rebuild from a mechanic that specializes in the hitachi and aisin carbs would be more cost effective than paying $400 for a mechanic who doesn't work on these carbs to take a crack at it.
 

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Discussion Starter #18
spark plugs arent old, only about 5000k, probably less. just finished a tank of fuel treated with injector cleaner, air filter is even newer (although its a cheap brand, been meaning to look into getting a K&N brand just havent had the money)... but i will look into replacing all the leads nd distributor...

nd i dont really have the mechanical know-how to remove the top off the carb. sorry, i thought i had mentioned tht i hadnt done that, obviously not... im not stupid so im sure i could work out how to, i just dont want to risk stuffing it all up is all... is it easy to do...? :s
 

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Sorry about that, I thought you had the hat off it already. Trying to do all of this stuff to the carb with it on is rediculously hard, and pulling the hat off is super easy to do. There's a wing nut on top of it that you remove, you pull the hat off with the snorkle and air cleaner lid all together. You don't need to remove the vacuum lines that are attached to the air cleaner lid, but you do need to pop the lid loose so you can move the hat off of the carb. The tricky one is the HIC hose that goes between the underside of the hat to the intake manifold right next to the carb. Make sure you cap it off or the engine won't run well (if at all) with that vacuum leaking. Don't forget to reconnect it when you put the Hat back on. Once the hat is off, you can see all of the carb linkages and springs and crap a lot easier. You can also see the choke plate and work it manually while spraying carb cleaner into it. While the engine is running you can work the throttle and the choke and clean all of the linkages and springs with carb cleaner spray, and get all the resin and deposits cleaned out of the barrel. Shoot the linkages on the back with some lube afterwards to keep them running smooth. The carb spray degreases everything.
It sounds like your mechanic already did all of this, but you can do it too when necessary. I usually clean my carb whenever I change my plugs.
 
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