rebootej

I bought a ’94 4runner with a 3vz-e V-6 engine and blown head gasket. I changed out the head gaskets and the truck runs except I can’t get the idle and the timing to settle down.

When I first started the engine after doing the work on it, it would rev up to 1500 rpms and then the idle would come back down too low after warming up. The entire time this was happening, the idle was also surging up and down about 100 rpms. I changed the fuel pressure regulator on the rail and then on start up, the engine would quickly rev up and down between 1200 and 1000 rpms. Once the engine warmed up the idle settled down but still surged between 750 and 800 rpms. Driving it, when I let off the gas coming to a stop, the idle dropped to 250 rpms almost dying and then back up to 500.

I just tried exchanging the throttle body with the one off my ’95 3vz-e which was working fine when that truck was wrecked in February. I did have the throttle position sensor off the ’95 throttle body thinking I might try it on the ’94 4runner. I put it back on the ’95 and lined it up to where it had been originally positioned. Now on start up, the idle sharply revs and then drops between 1100 and 1600rpms several times until the engine warms up. It revs fast enough as though somebody is pushing on the accelerator. The idle then settles down again to 750 with a slight surging still present. I’ve not been able to accurately set the timing with all the problems I’m having with the idle.

Any ideas where I should go from here to trouble shoot this would be helpful. Thank you.