84 tercel 4x4 idle surge after fast idle warm up?

[jaq]

Hello everyone. I have an 84 4x4 wagon with an idle surge problem. After coming off fast idle engine will surge until rpm is about 1200. Above that it runs great. I have checked for vacum leaks and find none. Thank you.

[Petros]

most likely cause is vacuum leak, so I would keep looking in the not so obvious places. Check the TVSV is working and not leaking, check the vac advance in the distributor (or cap the line off). verify if the flap valve in the air cleaner is working (it is vac operated), also check the EGR is functioning or capped off.

Good luck.

[ARCHINSTL]

Another possibility of a vac leak is a deterioration of the hoses from the manifold to the brake booster valve, and thence to the booster itself; both of mine leaked - and the OE clamps were not as tight as in 1986, I replaced the hoses and the clamps and all was well. These were very subtle leaks and did not affect braking.
Tom M.

P.S. I wonder - should vac "leaks" be more properly referred to as vac "bleeds?"

[jaq]

Thanks guys, I will keep looking for leaks. I appreciate the help.

[Petros]

Another possible cause, someone once found their throttle did not quite return to full stop because of weak spring, and carbon build up around the throttle plate. An easy check.