As the title says, I have a 1997 Toyota 4Runner, 3.4L V6, 4AT, 4WD. The problem originated as a bog at low throttle openings, and occasional RPM "hunting" at low throttle steady state cruising. Idle is fine, within spec. Eventually it threw a check engine light, pulled a P0505, Idle Air Control System. Figured the IACV needed cleaning, so I pulled it and cleaned it out with some throttle body cleaner. While I had it off, I noticed pretty severe corrosion/cavitation in the coolant passage on the TB side. I reassembled everything, and found the problem remained, so I ordered a used TB/IACV from eBay, pulled from a truck that died of rust.
Fast forward to today and I went to install the new used TB/IACV/TPS assembly. Starting it up, I got a high idle that wouldn't go away. I took it off again, cleaned the IACV that was jammed up with carbon, and reassembled. Truck idles fine again, but still has the bog at low throttle openings like it did with the old parts. Friend had a BNIB OEM IACV he was going to install in his truck, borrowed it for an afternoon, still same problem. Also tried swapping MAFs with another 4Runner, same problem.
Hooked the scanner up and looked at the data stream. Under ~15% throttle position, timing goes negative, varying between 0 and -8deg BTDC. Over 15.5%, timing jumps up to normal 20-30deg (in Neutral, no load).
I'm guessing this is a result of the ECU trying to bring the RPMs down from what it thinks is too high for the current throttle opening, and giving up once the throttle opening is above a certain amount.
So far, I've tried the new used TB/IACV/TPS, brand new IACV, spraying brake clean around the TB, 4 of the injectors (2 covered by upper intake), "air assist" hose and coupling behind the upper intake, and various hoses. The FSM says to jump T and Te on the service connector, disconnect and cap the air assist hose that goes to the IACV and esure the RPMs drop below 500. If it doesn't, it states there may be a leak in the air assist hoses, pipes, or injector seals. When I performed the test, nothing changed, idle remained ~700, within normal spec. No matter how much brake clean I sprayed on those hoses, pipes and 4/6 injectors, nothing changed.
I'm a little at a loss here. Should I replace injector seals? Anyone seen anything like this before?
Thanks in advance!
Fast forward to today and I went to install the new used TB/IACV/TPS assembly. Starting it up, I got a high idle that wouldn't go away. I took it off again, cleaned the IACV that was jammed up with carbon, and reassembled. Truck idles fine again, but still has the bog at low throttle openings like it did with the old parts. Friend had a BNIB OEM IACV he was going to install in his truck, borrowed it for an afternoon, still same problem. Also tried swapping MAFs with another 4Runner, same problem.
Hooked the scanner up and looked at the data stream. Under ~15% throttle position, timing goes negative, varying between 0 and -8deg BTDC. Over 15.5%, timing jumps up to normal 20-30deg (in Neutral, no load).
I'm guessing this is a result of the ECU trying to bring the RPMs down from what it thinks is too high for the current throttle opening, and giving up once the throttle opening is above a certain amount.
So far, I've tried the new used TB/IACV/TPS, brand new IACV, spraying brake clean around the TB, 4 of the injectors (2 covered by upper intake), "air assist" hose and coupling behind the upper intake, and various hoses. The FSM says to jump T and Te on the service connector, disconnect and cap the air assist hose that goes to the IACV and esure the RPMs drop below 500. If it doesn't, it states there may be a leak in the air assist hoses, pipes, or injector seals. When I performed the test, nothing changed, idle remained ~700, within normal spec. No matter how much brake clean I sprayed on those hoses, pipes and 4/6 injectors, nothing changed.
I'm a little at a loss here. Should I replace injector seals? Anyone seen anything like this before?
Thanks in advance!
