Gday all. Ive got an issue with the idle on my 4runner. This issue is only when warm and returning to idle from higher rpm, it wont do it until the coolant temp reaches 90-100c. The idle likes to drop off to the point where it almost stalls and then bounce back to 900(ish) rpm. It will do this about 5 times, with less of a drop in rpm each time until the idle settles at 850-900rpm.

My cold idle seems to sit a little high at around 1300-1400rpm? I thought it was supposed to be around 1100-1200. I spent close to an hour today with the car on a steep incline and a coke bottle jammed in the radiator cap, slowly refilling the coolant system while squeezing the bottom rad hose with the engine running and the heater on.

I also spent a fair amount of time trying to find a vac leak. Sprayed some parts cleaner all around the vac lines and didnt get an increase in rpm anywhere, but i can hear a "hissing" sound coming from the front left (looking at the engine from the front of the car) very hard to pinpoint with the engine running but it sounds like its tucked just underneath the intake manifold...but its all steel lines there, and i disconnected/plugged the diaphragm valve thing that sits infront of the egr thinking the spund was coming from that but it wasnt. The hiss could be the p/s pump but i dont think it is. I removed just about every vac line i could get to. Some increased rpm, others didnt. The strange thing was that some of the lines i removed had a very small amount of vac compared to others, yet they didnt change the rpm???

I havnt checked the resistance on the isc yet because there wasnt an issue before i did my isr+afm mod and changed the injectors.

I also noticed that when i applied the brake pedal, upon releasing it quickly the rpm would increase slightly and then resettle. Is this normal? This hissing noise also increases and decreases when adjusting the idle screw, but when doing so it sounds like it is inside the manifold itself.

Any ideas on what to check next?

 

Have you hooked a vacuum gauge up to check for leaks yet, If that checks out move onto the TPS and verify every thing is with in spec. LCE has a big article on the adjustment process that gives you a steep by steep run down.

 

No i dont have a vac gauge, although i should probably get one, given how cheap they are. And i used the wrong terminology before. I meant tps when i said isc (idle speed controller)

 

Any one else? Is the hissing noise when adjusting the idle screw normal? Should there be a small amount of vac in some of the lines that wont change idle when theyre disconnected or has something like a diaphragm let go somewhere?