Rough Idle In D, Voltage/RPM Drop

[Decaf]

It only does this once the engine is warm periodically and is remedied by putting the car in neutral.
RPM goes to ~1600 at start and takes about 5-10seconds to drop to 1200 on cold start.
RPM at idle is 1200 cold start, 750 after about 10min, 600-650 warm and will drop to 500 at lowest when at a stoplight.
ECTS has been replaced, stant thermostat, new WP, new dexcool, new IAT, cleaned TB/IAC/TPS, new ngk plugs (iirc), new delco wires, clean air filter, 3000m diligent oil changes, cleaned EGR. 130k miles.

I have no gotten a compression test, I'm not sure about tensioner/idler pulley but there is some noise coming from that area. Not sure how to check if motor mounts are good.

Tons of city driving so I get 20-25mpg and I take it easy.

Any ideas besides letting a mechanic try to diagnose?

[fdryer]

Simple belt/tensioner test; if you can deflect the belt with just your fingers then the tensioner is worn out. Most tensioners that wear out allow the belt to squeal in early morning starts until the belt warms up from friction. If the belt tensioner is worn out, replace the tensioner, idler pulley and belt, all at the same time. Good belt tensioners won't allow belt deflection with fingers.

[Puck head]

Mine was doing the same thing. I changed the fuel injectors starting problem solved. Surging rPm. Fuel pressure regulator another problem solved. Easy to do too. Ok the Injectors were a bit tricky but no that bad.

[Decaf]

Originally Posted by fdryer

Simple belt/tensioner test; if you can deflect the belt with just your fingers then the tensioner is worn out. Most tensioners that wear out allow the belt to squeal in early morning starts until the belt warms up from friction. If the belt tensioner is worn out, replace the tensioner, idler pulley and belt, all at the same time. Good belt tensioners won't allow belt deflection with fingers.

Yes i have the classic bird chirping sound in the cold morning starts. I'll go check that out today. To my untrained ears it sounds like its drive belt related or where the timing chain is under the valve cover/power steering pump.

[ssewall]

Testing the top mount depends on what type you have.



For the type on the right you put a straight edge on the surface where the valve cover meets the head, then measure up to it from the base of the mount. It should measure > 39mm. You'll need a straight edge to put on the top of the head to measure up to. It makes more sense when you look at it.

The frowny is measured by sticking a hex key in it's mouth A 2mm key should fit.

[Decaf]

Originally Posted by ssewall

Testing the top mount depends on what type you have.



For the type on the right you put a straight edge on the surface where the valve cover meets the head, then measure up to it from the base of the mount. It should measure > 39mm. You'll need a straight edge to put on the top of the head to measure up to. It makes more sense when you look at it.

The frowny is measured by sticking a hex key in it's mouth A 2mm key should fit.

Why am I measuring it? Pardon my lack of knowledge.


When you say "deflect" does that mean i the belt should have no give when tugged anywhere on the belt?

[ssewall]

You're measuring how much the mount has sagged from when it was new. The measurements I gave you are what the FSM authors have determined are likely to cause problems such as idle vibration.