I have a 2002 Chevy Tracker with the V6.  It sometimes takes several seconds of cranking to start then idles rough for a few seconds.  After that it runs fine.  I've heard of issues with the cam position sensor causing this.  Where is it located on the block?  any other ideas on what is causing this problem on my 110000 mile ride?

The cam position sensor is on the back of the head - I believe the left side (referenced from the driver's seat) - however, I'm not certain that that is the cause of your problem - fit a fuel pressure test point to the rail and check to see if you're losing pressure with the engine off.

What I think happens is that the fuel pressure in the rail bleeds down and then it takes several seconds to build up when you start cranking.

What you could also  try is switching the ignition on, but not cranking, two or three times before cranking - the fuel pump should run for arounds 3 seconds every time you switch the ignition on.

Did these slow starts occur on cool mornings?  My idle control valve (ICV?) went bad on my 2 liter last spring.  I noticed it was beginning to crank longer and longer to start in the morning and when it fired it would typically burble a few seconds and then die.  I would bump it once more and it would take off and run fine.  The valve for my 2 liter engine cost around $320, but was about a ten minute swap out.  Basically this small electronic piston/valve serves as a choke of sorts for cold weather starts.

If the problem is caused by the IAC valve, you should be able to overcome it by a small throttle opening (say 5%, although it's hard judging that with your right foot  , as the IAC's function is to control the idle speed by allowing a measured amount of air to bypass the closed throttle.  Perhaps just a short small jab at the pedal?

I have had this happen a few times, usually when its a cold day.  After repeated tries, I concluded that the plugs were soaked with fuel, so I cranked with the throttle wide open and it eventually coughed into life (just like what we used to call a "flooded carburettor").  It happens so rarely that I haven't pursued it, but it may well be a sticking IAC valve.

I was told these can be cleaned (the piston on the valve).  Mine was held on by two phillip head screws.  I pulled it off, sprayed choke cleaner on it to remove some of the carbon build-up on the surface and reinserted it, but noticed no difference.  I was told you need two people to check its function visually.  One to hold the valve and prevent the piston from over extending and the other to turn the ignition.  In any event, I ended up replacing the valve on mine and the extended cranking on cold weather starts ended.

Can some one take picture of it

It does it under all conditions but not all the time if it were the fuel pump I think it would do it all the time and this has been going on for almost a year.  Hasn't left me stranded yet.  It has a new fuel filter and plugs.  Gets 20mpg in town 24-26 open road

This is my old one.

I was told these can be cleaned (the piston on the valve).  Mine was held on by two phillip head screws.  I pulled it off, sprayed choke cleaner on it to remove some of the carbon build-up on the surface and reinserted it, but noticed no difference.  I was told you need two people to check its function visually.  One to hold the valve and prevent the piston from over extending and the other to turn the ignition.  In any event, I ended up replacing the valve on mine and the extended cranking before cold weather starts ended.

I'm puzzled by the carbon build-up, as the valve only passes air from the air filter - perhaps it's crankcase oil coming out with the blow-by gases which are fed back into the air inlet.  If it's a recurrent problem, perhaps the answer would be an oil catch tank.

I do not know.   There was considerable build up on the plunger end. 

The build up n the IAC valve is from the EGR system allowing exhaust gas back into the intake.

The build up n the IAC valve is from the EGR system allowing exhaust gas back into the intake.

That would be very surprising, because the recirculated exhaust gas enters the inlet tract downstream of the IAC valve, and there is a fairly long pipe from the IAC valve outlet to the manifold, up which the gas would have to flow against the airstream.

My guess is there is an unusually large anount of oil in the blowby gas.  Maybe valve stem seals are poor?

With 150k on my engine.... that is a very real possibility.  I bought it with 81K on the odometer and I noticed a couple indicators it had been rode hard and put away wet several times.  I've maintained him pretty well since but that doesn't negate prior abuse.