99 QX4 Hard to start - stalling - missing

[Avalanche325]

Hi everyone. Man do I need help.I have a 99 QX4 with 135K on it.

I was backing out of the garage and suddenly it started to shudder. I shut it off, and then had trouble starting it. When it did start, it would idle fine, but as soon as I touched the gas or put it in gear it would stall.

Symptoms: Hard to start (most of the time)Will idle fine in parkIn gear has an occaisional miss (when it stays running)Sometimes I can drive it for a short distance.I can rev it at partial throttleFull throttle will make it stallNo check engine light

I have spark. So I went for the fuel system. Good pressure at the pump.I changed the fuel filter, fuel pressure regulator, and then the TPS. I cleaned the MAF. It is still doing the same thing.I am now pulling my hair out. (works as well as anything else I have done)

It is still doing the same thing. Please help.

[carnal_c30]

Crankshaft position sensor? Might be somewhat functioning but not putting out a consistent signal

Try another MAF as well even if you clean it it could be bad

On my 2000 I had a similar problem it ended up being the distributor as I got random misfires yet when I checked it I was getting spark.Similar symptoms- difficulty starting sometimes no start, rough idle, and other times it just ran rough

[Avalanche325]

Update - it is not the crank position sensor. They sure put that in a fun place.I am putting in a new MAF tomorrow.

I was out of the country for two weeks. I was planning on having the MAF and CPS sitting on my doorstep when I got home from the airport. Only the CPS was here. Crap.

[Avalanche325]

Just to finish the story in case it helps someone in the future.

It ended up being the cam position sensor. Of course the most expensive thing. I replacd the distributor and away she went.