rough idle

Eatpants · Post by **Eatpants** » Sun Oct 23, 2005 6:15 am

rebuild a carburetor on an 86 sr5 wagon, hoping to fix the rough idle, it goes up and down and drops too low and dies

any ideas?

MootsMan · Post by **MootsMan** » Sun Oct 23, 2005 11:00 am

Have you checked all your vacuum lines to make sure they are all connected and connected properly ?? Also, the hose that goes into the HIC valve on the underside of the air breather can cause idle problems if it is not connected.

xirdneh · Post by **xirdneh** » Mon Oct 24, 2005 2:11 pm

Eatpants wrote: rebuild a carburetor on an 86 sr5 wagon, hoping to fix the rough idle, it goes up and down and drops too low and dies

any ideas?

try disconnecting the "b" vacuum switch hose on inside of right fender
sometimes this works
do not know why
if it does work
leave it disconnected
have not noticed ant differences

other than that you may have left out a spring in carb when rebuilt

GTSSportCoupe · Post by **GTSSportCoupe** » Tue Oct 25, 2005 9:23 am

Eatpants wrote: rebuild a carburetor on an 86 sr5 wagon, hoping to fix the rough idle, it goes up and down and drops too low and dies

any ideas?

If you don't find any vacuum leaks etc., you could drill out the idle mixture plug, and adjust the idle mixture to smooth out the idle. You may have to adjust your idle speed too.

Eatpants · Post by **Eatpants** » Tue Oct 25, 2005 12:13 pm

it did the same thing before the rebuild
which is why i decided to rebuild it in the first place haha

mixture plug has been drilled out from whoever rebuild it last, they did a keen drilling job too (sarcasm) but it works

whats the B vaccum hose?

xirdneh · Post by **xirdneh** » Wed Oct 26, 2005 9:13 am

Eatpants wrote:

whats the B vaccum hose?

on the right inside fender next to the coolant container
there are two switches with vacuum hoses attached
one is the "a" switch the other is the "b" switch
the "b" is usually (but not always) the forward one
its hose usually attaches to the metal vacuum line located just to the right of the EGR valve.
i do not know its purpose
but it has solved idleing problems for me on several cars
the symptoms were erratic idling and engine dying unless idle was cranked up
pretty high

Post by **ARCHINSTL** » Wed Oct 26, 2005 2:29 pm

Vacuum switch "B" is attached to a vacuum line which runs from the TVSV to the Choke Breaker. So apparently it must control vac in some way to the CB - possibly by introducing varying (?) amounts of air into the system, thereby modifying the diaphragm's action inside the CB against the vacuum supplied to the CB from the carb - kinda like what the modulator does to the EGR valve. The introduction of air is a guess on my part, as the FSM is characteristically mum on what it does.
It is apparently told what to do by the ECU, with possibly some influence from the EBCV. I looked at the chart from AZ's site (or the FSM), and that is where the thing is hooked (I can't read electrical charts well, though). One thing - the "B" switch is shown in those charts, but on the page about the CB in the FSM, it is not present in the drawings; it is as though the TVSV alone controls that side of the diaphragm - presumably this is wrong.
I checked the 2 vac switches by the method in the FSM (or the excellent repair info on Autozone's site); mine work, per the continuity tests, so I did not investigate further. Maybe attaching/detaching the tube or measuring the vac with a gauge whilst observing the CB's lever would help. Possibly also making sure the switches' grounds are clean might help.
As MootsMan suggested, you might check the HIC valve to see if it works. Mine did not, and on replacing it ($63-OEM), the idle improved. This would seem like a good item to snatch from the yards-I think the Corolla used this same valve, too.
Tom M.

Eatpants · Post by **Eatpants** » Wed Oct 26, 2005 2:45 pm

B vaccum switch was already removed and plugged on both ends so i guess i should mess with the mixture now? any other ideas?

thanks

Eatpants · Post by **Eatpants** » Tue Nov 08, 2005 5:30 am

yesterday the same thing happened to my blue tercel

naturally i love that car a ton more than the silver one so i attacked the mixture adjustment, seating the screw fully as said in the manual, then backing out 3 and 1/4 turns... now the screwdriver i used really sucked but i know i got somewhere near 3 turns

made a VAST improvement, but still not nearly as good as it was running a month ago (grrr) i ran a can of seafoam through it before i went out of town last week (3/4 can in tank, 1/4 in crankcase) anyways i guess that messed something up, but at least now i know what will fix the silver one!

our family is having huge ridiculous car issues right now, brothers mustang third cylinder craps out, doesnt even run now just starts and dies. trucks clutch barely grips anymore, firebird overheats and guzzles gas, so basically my entire family counts on my blue tercel for transportation

we need to win the lottery