Hard Start

Toyota can't seem to get a break with intake manifolds: lots of reports of third gen manifolds clogging up, likely due to Exhaust Gas Recirculation.

 

76k though, makes me wonder if usage has anything to do with it.

 

Well, I suppose I would first try to figure out what needed to be cleaned. If you are just referring to the oily residue visible as you look past the throttle plate into the manifold, I would leave that alone as normal. My 2004 has logged 196K miles, I've cleaned the throttle body interior a couple of times and the MAF sensor once, and that is it.

If the engine runs "fine" from time to time, then I doubt that cleaning is the issue. It could be that a manifold gasket is slightly leaking depending upon temperature, and allowing unmetered air into the intake manifold. If so, that would cause a lean air/fuel mixture which would result in the engine running rough.

In general, cleaning would involve removing the aluminum intake manifold, then running a solvent through it - like paint thinner or kerosene. You could use a small paint brush to apply the solvent and scrub off any accumulated dirt. If there is a small area to be cleaned, brake parts cleaner spray would be highly effective. You do not want to use any of those solvents while the manifold is mounted to the engine intake.

If this were my car, I would remove the manifold and replace the two gaskets: the one between the throttle body and the manifold, and the other between the manifold and the engine head. I would also clean the manifold but that cleaning would be motivated more by cosmetic reasons and less because cleaning would actually help the engine performance.