how to adjust idle on 88 celica gt

Idle on that 3SFE is not intended to be adjusted. There is an air bypass screw under a black rubber plug on the throttlebody, however if you turn it out to increase idle rpm, the ECM will just compensate over time with the ISC controller. You could have a bad engine mount(s)... on newer Celicas it is common for the mount near the timing cover to cause a heavy vibration at high mileage/high age. Being a 1988. I would suspect that mount simply due to extreme age even though the '88 style isn't historically as bad about failing.

Toyota MDT in MO

Why not just fix the problem? A tune up including a distributor cap and rotor can do it wonders. Vibration can be a bad mount too, but something still has to set it off.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >

I assure you that a properly running 3SFE in a Camry or Celica of that vintage will vibrate badly in gear if the passenger side mount is collapsed. Its not as much of a problem on the 86 to 89 Celicas due to the design used in that year range, but still a strong possibility.

Toyota MDT in MO

'In gear'???

Well if he has an automatic, he 'sure' doesn't want to boost the idle way up then, that will cook things.

I was just thinking in neutral. If an automatic, I would check out the mounts first.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

Why not in gear? The OP didn't state stick or auto. I see more autos in that model so I gave a likely culprit based on experience. Yeah, if it is running rough under no load I would suspect a fuel or ignition problem too. I haven't exerienced those engines idle no load

"Something still has to set it off" ?????????????????????????? I have customers come in all the time wanting tuneup work because their engine is "running rough" at idle. 95% of the time the cause is vibration transmitted through the motor mounts AND NOTHING ELSE. A bad cap and/rotor would cause plenty of problems above 650 RPM. On Toyotas we always look at the mount at the timing cover first. We check it by putting a block of wood under the oil pan and jacking up the engine slightly. When the collapsed, bottomed-out mount is unloaded the vibration decreases radically. Don

Yep, I prefer using a large prybar placed under the right mount bracket, fulcrum point on the radiator support area with a rag for paint protection. It's a little quicker than the jack and block method.

Toyota MDT in MO

If I am sitting there with the hood open and see an engine 'vibrating like crazy' and up the idle to 1000 rpm and it stops vibrating, I think tune up, especially the cap and rotor or maybe a bad plug or wire. Folks forget about cap and rotors too often though, so I start there.

Now if the fool is loading up the torque converter on an automatic to smooth out the 'idle' like comboverfish implies, then I would think mount.