Actually I have seen this on a number of different engines, My 20R motor is original and has about 148K on it... It shakes at idle noticeably and I was wondering what could cause this? Vacuum leak? Valves out of adjustment ( they do clack alot) Low compression? I pulled my plugs and changed to a better plug wire but no luck, still shakes and shimmies.. Seems to run OK... I checked the timing and with the vacuum line off the distributor, I timed it to 8 degrees BTDC.. Now what?? Thanks for your help in advance!

peter

 

shakes liek what? engines vibrate.... are your motor mounts in good order?

 

i was going to say motor mounts but it might be just outta balance. mines shakes noticably more now that it doesnt have 40 pounds of airconditioning on one side. at least thats what i attribute it to.

 

is the motor shaking? could have a plug misfiring -- did you just pull the plugs and put them back in or change them? replace the cap and rotor? 8*btdc is factory timing spec.

a/c on or off the engine won't make a difference.

 

did you ever find out what the problem was?????

 

*subsribes* my 81 does the same thing...

should this be in the 3rd gen section?!

 

I installed a new intake manifold gasket and the shaking on my 20r is gone. Hope this helps.

 

My truck has always had a pretty rough idle, I dont really pay attention to it anymore.

 

my old 20r had a bit of a shake at idle even when it was run good

I think it is a 20r trate but my old 20r had 15 psi spread on it compression

do a compression test

remove all the spark plugs then test each cylinder

 

I've got a '78 Celica with a 20R in it, and it too shakes quite a bit at idle. It smooths out nicley once it gets going, but it's funny to watch the motor motor vibrations get passed all the way back to the shifter sitting at stop lights. I should "almost" get a shaker hood for it

 

i think it's something with the carb typically, probably the mixture. come to think of it, my buddy's old '78 pickup shook like crazy, but i always thought it was something to do with the fact that the bed was close to falling off

 

You need to adjust the valves first, then do a compression test. If its in a good state of tune (no vacuum leaks, choke not stuck, etc) and this don't clear it up or find a problem, it will either be:
1. the A.A.P (auxiliary accelerator pump) diaphram is leaking and causing the rough idle. Located on the valve cover side of carb, cup shaped, held on with three screws with one vacuum line coming off it. Disconnect vacuum line after running engine, if its wet inside or smells of gas you found the culprit. You can replace it or put a BB in hose with no adverse effects.
2. Trash in float bowl, easiest way to clear up is to remove air cleaner lid. Get a large rag that wont get pulled into the carb, crank up engine, rev it up pretty good by hand operating the throttle on the carb. With rpm still up, completely cover the carb opening with rag while you hold throttle wide open. Just before it dies, remove rag and release throttle (don't let it quit). Do this a few times, I've seen it and done it quite a few times and it works. It will pull a vacuum on the carb internals and draw most of all the trash out.
(ex-Toyota dealership mechanic, but still remember a few tricks for the 1980's models)

 

never mind i wrote what the guy before me wrote. he's prolly a genius like myself.

 

yay old post