Odd idle
01-11-12, 02:35 PM
#1
Odd idle
Alright so earlier today I went out to start the car just to give the engine a little exercise. So I went out pulled the choke out all the way put about 8 pumps in and started the car. The car started normally and idled at 3 thousand rpms like I normally have it do.
So here starts the weird part. I got out of the seat and started to walk away from the car to go check on something else and then the engine started to die, I ran back over to see the engine speed died to 2,200 rpms and then slowly started to make its way to 2,500 and stayed there till the choke turned off (When i say "die" I mean a sudden drop in rpms). The choke turned off at the right point and the engine went to idle. My car normally idles at 800 rpms due to a mechanic back in the day when by dad had the car serviced in the 80's and now idles around a thousand when I put in the new air filter. The engine went to a thousand rpms then sputtered to 600 then back up then down to 500 then back up to a thousand. I shut the engine off immediately when this started to occur.
I took a video and will upload it shortly. I have to switch computers due to my laptop not wanting to read my camera. The video was taken shortly after this occurred.
So here starts the weird part. I got out of the seat and started to walk away from the car to go check on something else and then the engine started to die, I ran back over to see the engine speed died to 2,200 rpms and then slowly started to make its way to 2,500 and stayed there till the choke turned off (When i say "die" I mean a sudden drop in rpms). The choke turned off at the right point and the engine went to idle. My car normally idles at 800 rpms due to a mechanic back in the day when by dad had the car serviced in the 80's and now idles around a thousand when I put in the new air filter. The engine went to a thousand rpms then sputtered to 600 then back up then down to 500 then back up to a thousand. I shut the engine off immediately when this started to occur.
I took a video and will upload it shortly. I have to switch computers due to my laptop not wanting to read my camera. The video was taken shortly after this occurred.
01-11-12, 02:46 PM
#2
Alright I reviewed the video and it didn't catch the problem making it useless. But, before the video started to record I went to turn the key and the engine wouldn't turn over and it sounded like some one stuck a wrench in a bunch of gears. The video catches that point on, showing my car running just fine with no problems making it useless and not worth uploading.
It has been pretty cold here in Texas and I don't know if something got stuck and just needed to be used for a little bit or if this a serious problem.
It has been pretty cold here in Texas and I don't know if something got stuck and just needed to be used for a little bit or if this a serious problem.
01-11-12, 04:37 PM
#3
It's supposed to do that.
On an SA, ~ 130 secs or less (temperature dependent) into a full-choke run, the car's supposed to drop initial idle RPM slightly (about 500 rpm drop), and then it will slowly rise in RPM as it warms completely up.
Mine does it within only a couple seconds post-start, but it's never all that cold around here. I usually end up feathering the choke by hand a bit as it warms, as I don't like letting it run no-load much above 2000 rpm or so.
You shouldn't need to be pumping the accel pump 8 times before starting, though; all that's required when everythings right is, turn key to on, pull choke full out, wait a few secs for the bowls to fill, and then turn the key & let it spin a couple times.
On an SA, ~ 130 secs or less (temperature dependent) into a full-choke run, the car's supposed to drop initial idle RPM slightly (about 500 rpm drop), and then it will slowly rise in RPM as it warms completely up.
Mine does it within only a couple seconds post-start, but it's never all that cold around here. I usually end up feathering the choke by hand a bit as it warms, as I don't like letting it run no-load much above 2000 rpm or so.
You shouldn't need to be pumping the accel pump 8 times before starting, though; all that's required when everythings right is, turn key to on, pull choke full out, wait a few secs for the bowls to fill, and then turn the key & let it spin a couple times.
01-11-12, 11:22 PM
#5
Allow me to cite the 1980 owner's manual for you, just to put your mind at ease:
Page 3-4, Form No. 8155-00-79F, Mazda Model '80 Owner's Manual
Page 3-4, Form No. 8155-00-79F, Mazda Model '80 Owner's Manual
In cold engine starting, the choke **** is automatically returned halfway in about one minute from engine starting and then returned completely when the engine is thoroughly warmed up. In warm engine starting, the choke **** is automatically returnd completely after a short period of time from engine starting.
01-12-12, 06:32 AM
#6
Intresting. I've never experienced this phenomena. Normally, I only adjust my choke to rev 1,500 or so but it never drops off and climbs. Only shuts off when up to temp. Wonder if it would act different if I increased the RPM's? 3000 seems awlfully high though. Old carburated bikes and cars with manual chokes can have "personality traits". A series of steps if you will, that seem to make a cold startup more consistant. It used to be more common-2 pumps of the throttle, set the spark to full retard, half choke, hold your tongue just right and she starts on the first kick everytime!
I notice slight quirks (differences) between my cars and what they seem to better respond to while starting. I chalk it up to slight mechanical/carburator differences between them. Overall, I have developed the habit to pull the choke out most all the way, then turn the engine over while simultaneously feathering in the choke and applying some throttle. After the fire is lit, I adjust to 1500 rpms to warm up, then idle about 600/700.
I notice slight quirks (differences) between my cars and what they seem to better respond to while starting. I chalk it up to slight mechanical/carburator differences between them. Overall, I have developed the habit to pull the choke out most all the way, then turn the engine over while simultaneously feathering in the choke and applying some throttle. After the fire is lit, I adjust to 1500 rpms to warm up, then idle about 600/700.
01-12-12, 07:44 AM
#7
Senior Member
iTrader: (1)
Join Date: Oct 2011
Location: Florida
Posts: 320
Likes: 0
Received 0 Likes
on
0 Posts
It's supposed to do that.
On an SA, ~ 130 secs or less (temperature dependent) into a full-choke run, the car's supposed to drop initial idle RPM slightly (about 500 rpm drop), and then it will slowly rise in RPM as it warms completely up.
Mine does it within only a couple seconds post-start, but it's never all that cold around here. I usually end up feathering the choke by hand a bit as it warms, as I don't like letting it run no-load much above 2000 rpm or so.
You shouldn't need to be pumping the accel pump 8 times before starting, though; all that's required when everythings right is, turn key to on, pull choke full out, wait a few secs for the bowls to fill, and then turn the key & let it spin a couple times.
On an SA, ~ 130 secs or less (temperature dependent) into a full-choke run, the car's supposed to drop initial idle RPM slightly (about 500 rpm drop), and then it will slowly rise in RPM as it warms completely up.
Mine does it within only a couple seconds post-start, but it's never all that cold around here. I usually end up feathering the choke by hand a bit as it warms, as I don't like letting it run no-load much above 2000 rpm or so.
You shouldn't need to be pumping the accel pump 8 times before starting, though; all that's required when everythings right is, turn key to on, pull choke full out, wait a few secs for the bowls to fill, and then turn the key & let it spin a couple times.
Trending Topics
01-12-12, 05:34 PM
#8
The only reason I put in 8 pumps was because it hadn't been ran in a coupe months (school and work suck) so it would be easier to turn it over. I normally put in 3 or I just turn the key and it starts fine in the warm Texas weather.
Just too add this in, back in the 80's my Dad took the car in to have it looked over at a Mazda dealer after he got back from Italy (he was stationed there for a couple years) and the mechanic messed with the carb and screwed up the mixture so now it idles hard around 2000 rpms.
Once spring shows up I'm heading down to Rotary Performance to fix the mixture.
Just too add this in, back in the 80's my Dad took the car in to have it looked over at a Mazda dealer after he got back from Italy (he was stationed there for a couple years) and the mechanic messed with the carb and screwed up the mixture so now it idles hard around 2000 rpms.
Once spring shows up I'm heading down to Rotary Performance to fix the mixture.
Last edited by Redliner223; 01-12-12 at 05:41 PM.
01-13-12, 09:53 PM
#9
Back on the Road
Join Date: Jul 2007
Location: Austin
Posts: 355
Likes: 0
Received 0 Likes
on
0 Posts
You can do it yourself. Mine idles at 750 all day and all night. Whether its 105 or 25. Haven't messed with it in about 2 years. Just make sure you tighten the nuts on the idle screw.
01-13-12, 11:16 PM
#10
The throttle stop screw should be set so that the primary plates just barely rest on the venturis. You don't want them open too far or they will destroy your mixure. Closed too hard and they can warp against the venturis causing an air leak more or less. Once you have the idle dropped to 750-800 via the throttle stop screw (located under the throttle cams on the backside of the carb) you can fine tune the mixture using screw on the driver side of the carb.
Reference...
http://sterlingmetalworks.com/tuning_the_nikki.htm
Reference...
http://sterlingmetalworks.com/tuning_the_nikki.htm
01-13-12, 11:54 PM
#11
Junior Member
Join Date: Jan 2009
Location: Lincoln, NE
Posts: 44
Likes: 0
Received 0 Likes
on
0 Posts
How long has it been since you put in new spark plugs? The stock plugs get oil fouled very quickly, and a new set makes a big difference in idle. This could explain a change in how your car has been idling. I went too many miles without changing mine one winter, and the car refused to start at all. New plugs made it fire right up and idle smooth.
Sitting often without being run could contribute to your plugs getting oil fouled. Oil can sneak past old seals into the combustion chamber, and it contacts the plugs when you start it up after the car sits.
Sitting often without being run could contribute to your plugs getting oil fouled. Oil can sneak past old seals into the combustion chamber, and it contacts the plugs when you start it up after the car sits.
02-05-13, 09:08 PM
#12
Full Member
Join Date: Sep 2012
Location: nowhere
Posts: 127
Likes: 0
Received 0 Likes
on
0 Posts
My dd started to idle up about 500rpm when i got off work today and when i loosened the rpm screw to bring it down to 800rpm the motor was bogging. Ps i have 83 12a small sp
Atkins seals and boost prepd nikki not turbo yet
Atkins seals and boost prepd nikki not turbo yet
Thread
Thread Starter
Forum
Replies
Last Post
LongDuck
1st Generation Specific (1979-1985)
12
10-07-15 08:12 PM
