eagleusa24

What's up guys!!

I have a 1986 4runner and I'm having problems with it. When the engine is cold and start it, it runs fine. But when the engine is hot and start it, it runs fine to slightly rough but when I press the brake pedal the engine shakes, it rocks badly but if I put the reverse or drive gears since it has a A/T, the engine starts running fine. Does anyone know what the problem could be?
Also I'm looking for a back bumper for the same truck, does anyone know where I can find one relative cheap?

misterzee

My first instinct would be to examine everything vacuum related, the hoses, VCVs etc for a leak, or a valve stuck open. EGR system is highly suspect based on your symptom. I assume everything is "in tune" ? plugs, wires, timing, valve adjustment.... ?

toyminator2000

Maybe brake booster vacuum leak.

eagleusa24

Perhaps, it's the timing. I recently replaced the power steering pump which is right next to the distributor maybe I messed up the timing. I just replaced the plug wires, rotor button and distributor cap thinking that would fix the problem. I'm going to check the EGR system, is there a way to check the condition of the EGR valve? if a valve is stuck open, how can I tell?
If I have a booster vaccum leak, wouldn't that affect my braking?

abecedarian

When saying it runs fine when cold, we need to clarify things.....
... when cold started, after a few seconds the idle should be anywhere between 1000-1600 rpms (depending on the actual coolant temperature), then the idle should gradually come down to 750-850 after 5-10 minutes of idling. That's idling "fine" when cold (the colder it is, the higher it should idle when cold).

If it's not doing that, you should (well, you should anyways) adjust the idle speed to spec while the timing is set to spec (should be around 5 BTDC, with the diagnostic plug jumpered). Keep in mind that the timing and idle speed spec's are set with the engine fully warmed up- the thermostat has cylced a few times and the coolant in the radiator is actually warm-to-hot. Also, this is considering the stock 180/185F thermostat. A warmer or colder thermostat may affect idle speed significantly.

Once that is taken care of, we can start addressing the other issues....
but you say the engine idle, when the engine is warmed up, fluctuates / becomes rough, if you touch the brake pedal. That implies a vacuum leak caused by either the brake booster or excessive wear in the pushrod from the brake pedal to the brake master cylinder.