When temperatures outside get below 30 or so my 2001 4.0 SOHC runs awful. While driving the engine will stumble violently at times. The best way I can describe it is as either the biggest misfire you can imagine or kind of like you turned the engine off and then popped the clutch to get it started again. No check engine light yet. Does anyone have any experience with this kind of problem?

 

It is usually the ECT sender. The computer probably thinks the engine is warmer than it is, and is adjusting the fuel trims and ignition timing accordingly, which results in very poor performance, it may or may not clear up as the engine warms.

 

You could also check the gaskets between the parts of the intake manifold. There were problems when the engine is cold and shrinkage occurs, allowing extra air to leak in. I do not remember the vintages affected.
tom

 

I concur. The '01 SOHC is for some reason more prone to intake gasket leakage than the newer SOHC models. Probably because Ford upgraded and improved the intake gaskets a few years ago. So when you go to replace them, make sure you use Ford gaskets.

 

check the pcv tube rubber elbow at the passenger side front of engine, it likes to rot out.

 

Are you saying that it runs ok at OAT's above 30F ?????

 

Yes. It runs perfectly unless its really cold.

 

OK, good feedback, so when the OAT is above 30F te engine runs normaly & you don't have a CEL lit, so all that kinda suggests to me that the engines sensors may be ok & the problem is something the computer isn't monitoring.

So I kinda like Rockledges' idea about the intake manafold gasket leak.

To check it, when it's acting up, you could rig a propane "sniffer" with a length of tubing & a metal "sports needle"(the kind used to inflate foot & basketballs), as a probe & pass it around the intake manafold gaskets & see if you can spot a vacuum leak.

The propane is sensor safe & if the engine inhales it through a vacuum leak, it will cause the engine to smooth out, or the RPM to rise & with the needle, you should be able to pinpoint the vacuum leak.

Seeing as how it seems to be a intermittent problem & if it's a intake manafold gasket leak, if the intake gasket hasn't been sucked in & it's just a loose fastner, you might be able to get away with a re-torquing of the intake fastners, to seal it.

If it's not the intake manafold gasket, be sure to probe the vacuum lines, connections too.

I also like the check the PCV valve idea too, as it can freeze, or stick open & in effect cause a uncalibrated vacuum leak, until it thaws out, or warms up & unsticks to begin working normally.

Let us know how it goes.

 

Thanks for the good info.

It looks like its going to warm up here next week. 50's & 60's every day. It might be awhile before I can track this problem down, but I certainly appreciate everyone helping me know where to start when it begins happening again.