5vz fe high idle and rpm pulsating.

This saga started about three weeks ago. Cel came on for IAC valve. I disassembled completely, cleaned all contaminates and rebuilt with new rtv, IAC seal and TB seal. Except I put tension spring to paint marker mark that Toyo marked with. This resulted in idle at 2k. So I changed it back to stock position. Both times leaving battery unplugged for 20+ min to reset ecu.

That resulted in engine pulsating between 1200rpm and 2000rpm randomly. Idle at 2000rpm, and just overall shit engine response. Engine also would maintain rpm for a couple seconds even after clutch pressed in.

Since I first touched IAC I was getting cyl 6 misfire, except when I rebuilt second time I'd get cyl 5. Also get general misfire
If it was cold I'd also get any random combination of cyl misfires. And codes only popped up at initial start/warmup. I'd clear and be fine for rest of drive.

So, I replaced IAC with a airtex/wells, plugs/wires/MAF/coil on cyl3/5 with denso. Coil on 3 was autozone special so now they are all denso.

Now it idles at 1200, minimal pulsing, minimal rpm throttle lag, but idles at 2000 with ac on.

Originally idles at like 800 with ac off. And maybe 1050 with it on. 1200 was highest ever at idle. And it drove like a slug.




So what's left? Now I might get a general misfire every 100 miles. Vacuum lines are good.

Cam position sensor? Ecu fault? I want to say not injectors as the issue moves between cyl 5 and 6. And lately cause it's running so hard I can smell coolant when I get out. Timing belt/pump/seals were changed 35k miles ago by a Toyota shop. Truck has 225k miles and I'm not ready to let it die.

 

To me it sounds like you have a vacuum leak going that high and back down.. When you reset the ecu the computer must RELEARN idle. Mine did the same thing with I replaced mine but after the second day it was idle at 750 rpms.. It can take it day or 3 days...


If your smelling coolant you might want to check your coolant lines on the Ica and confirm they are on tight or you don't have a leak somewhere else like in the valley of the block for example or a hose starting to drip on the back side hitting the exhaust..


What other codes is it telling you just fire misfire... There has to be other code in there.


Edit one more you could have a leak on the metal gasket from the throttle body to the plenum..

 

Hrm I'll give it all a once over again. No longer throwing any codes though. Even if I push it.

 

Only other thing that would keep the engine high could be the cam or crank sensor ( as in your op). To check those correctly you really need a lab scope to see if you having a drop out causing the ecm to jump... You can do a ohms check to make sure they are in spec tho.


Cel is great but the ecms on Toyotas are sometimes weak when it comes to drop outs and picking them up and storing them and giving you a cel light..

 

Found source of coolant burning smell. Heater control valve hose is leaking. Is this somehow tied into the vacuum system or directly affect rpm?

 

Only way the coolant could be effecting the rpms change is if the coolant was leaking say on the electrical (injectors for example) making a short circuit. Make sure your coolant level is topped off since you found one source.


I would double check your vacuum hoses and make sure you don't have one cracked or is loose on the fitting.. If the hoses are the ones when it was from the factory I would change them.