Rough Idle after changing intake manifold gasket

[skothar]

To make a long story short (can provide the back story if anyone is interested), I changed the intake manifold gaskets on my 3.0 V6 2004 Ranger. The truck has 165,000 miles. Since then, the truck has idled rough. The truck ran smooth before the repair. It runs OK at higher RPM and there does not seem to be any loss of power.

I pulled the valve covers off and rechecked the rockers and the torque on the fulcrum bolts. Everything looks and feels OK to me.

Things I have done to try and smooth out the idle:
- new fuel pump and fuel filter (I needed this anyway. The truck would not start on hot days, and this seems to have fixed that problem)
- SeaFoam treatment
- Techron treatment
- checked all the injectors. They test within spec.

There is a P0430 code (oxygen sensor), but that code existed before the repair when the truck ran smooth.

When I did the intake manifold off, I had to move some wires out of the way. I noticed the leads that go to the coolant temp sensor had brittle shielding. I wrapped them in electrical tape. Is it possible that there could be a short from the temp sensor causing this?

I'm also wondering if the cam position sensor is bad. From what I've read that can cause rough idle. But it seems odd this would crop up after the manifold was changed.

Basically, what about changing the intake manifold could result in a rough idle?

Many thanks.

 

[skothar]

I might have fixed it! Yesterday while doing an oil change i decided to double check all the hoses and electrical connections. I discovered that the EVAP canister purge valve was broken. The previous owner had tried to epoxy it, but the epoxy had failed, so there was a significant vacuum leak. I replaced it. I idled the truck a little after completing the oil change and it seemed smoother. I'll be leaving on my morning commute in about an hour and see how it runs over all.