Expert: Sean Halliday - 8/9/2009

Question
94 Nissan Altima 220,000 miles.  Wouldn't start one morning. Did compression test (on cold engine) Very low on first cylinder and gradually better on up, but all pretty low.  Maybe jumped the gun and did a head gasket and got a valve job.  Now compression is 135-145 all the way across (Still on cold engine).

The only way we can get it to start is to keep cranking it for a while punching the gas every now and then.  It sometimes finally catches and will purr like a kitten. As  soon as the RPM drops below 2000 it quickly dies.

No Computer Trouble codes.

Disconnected O2 sensor - no change
Disconnected exhaust at exhaust manifold (in case of cat. blockage) - no change (not sure if this is a valid way of ruling this out)

I am assuming that since it will run at higher RPM the timing chain is set ok.

Couldn't find any vacuum leaks visually. Spraying starter fluid in the intake has no effect.

EGR Pops in and out when I squeeze it.  Not sure how to check IAC or what else to look at.  Could I have messed up the intake manifold gasket when I put it in?

I am learning a lot of this as I go along. Thanks for your help.

Answer
Poor idle can be the IAC,but this is more like a fuel problem.Did you check the pressure regulator?Also check the fuel pressure.Checking the iac is simple.Remove it from the engine and hook it up to a 12 volt source to see if the electro magnetic motor is moving the little piston.You will hear it click and see it open and close.Best to get a good manual and go through all the fuel and ignition components one at a time.The head gasket and valve job was due so it should run better.This will probably be a bad fuel pump or regulator.Replace fuel filter before checking pressure.There many things to cause this such as cam sensor,maf,map,egr,fuel pressure and so on.