IMRC Codes/Cooling System Issues

So my mothers '96 3.8L Windstar is having yet more troubles here. Started out with some fuel system issues causing difficult starts in which we had to replace both the fuel pump and filter and that solved that problem and the van cranks right over now without a problem.

Now for the longest time, an issue has been going on where the heater does not provide any heat when sitting still and only does so when the van has been moving for a decent amount of time. On top of that, it's also had the IMRC codes P1537 and P1538 triggered for the longest time which we haven't had a chance to diagnose or fix for that matter.

Recently she had the thermohstat changed just for the hell of it since someone mentioned the original one possibly sticking in the open position. Not only that, but I don't remember it ever being replaced since she's owned it and she's put about 40K miles on it since then easy. It's at about 115K right now thereabouts. this WAS a common problem on her old olds cutlass sierra circa '90 or so which always seemed to require a replacement thermohstat every few months or so.

Anyways, one day last week, BEFORE the thermohstat was replaced, it overheated on her all of a sudden while at a dead stop in the usual sub-50 temps around these parts (Northeast Ohio fyi). It did this once before a few years back during these cold temps in rush hour traffic where the temp guage spiked and a simple coolant flush fixed it right up. So far it hasn't done anything this week and has been running just fine. But the no-heat issue is still going on. Also, I'm not up on nominal coolant temps, but a few weeks back during a trip to Columbus, I had my laptop hooked up during the full trip via a Scantool.net device and the coolant temp off the PCM was constantly hovering around 190-200 during highway speeds, no A/C. May be a misnomer, but I figured I'd put that out there for diagnosing.

Anyways, She's planning to take it into the local mechanic tomorrow on her day off and he already mentioned it sounds like a blown head gasket or something similar. I've already done some research on here and have told her to make it perfectly clear to the guy not to make a big deal out of the head gasket but check the lower intake manifold instead due to the fact made clear here that the head gasket design was imrpoved between the '95 and '96 years and is not nearly as high of failure rate as it once was.

I'm just curious if theres any more diagnosing that could be done here with this. Also, due to the close physical proximity of the IMRC actuators and runners and the lower intake manifold, I was curious if there was any possibility of these being linked.

EDIT: Oh. I should also mention it still has a rough idle on a warm start that constantly threatens to stall. Runs fine from a cold start though. I somewhat relate this to the IMRC problem, though I may be way off base.

Rough idle on warm start could be from coolant leaking into the intake after you shut it down.
I had that with mine until I took care of the lower intake manifold gaskets.....
The coolant is then drawn into the engine....causing the rough idle.

The only way that I see a connection between a coolant leak would be, again, with leaking lower intake manifold gaskets......
Mine caused a buildup of gunk in the lower intake.....including on the IMR butterflies for cylinders #1 and #4, which is where the leak was.
Maybe the buildup is bad enough to cause the plate to hang up, causing the shaft to not move the full expected travel distance.

The heat issue could be caused by air getting into the cooling system.....which will cause the overheating and / or no heat issue.
Take note that leakage from another location, such as the front cover (aka timing cover) or even a loose hose clamp will cause the same issues of heat and engine temperature.
IF the hoses are original.....I would give them a very careful inspection.....including the heater hoses, and the short elbow hose that is on the pipe that comes out from the top of the water pump....goes toward the firewall.......the elbow is the one that turns toward the radiator...connects to a pipe that goes into the center of the lower intake manifold.

Just out of curiosity, you might check and see if you have low speed fan function.
With the vehicle in Park, turn on the A/C, and raise the hood to see if the fans are running.
If not.....it could be the low speed dropping resistor for the radiator fans.
I have pictures of that in my pictures.

Sorry about the late reply, but thanks for the advice. As it stands right now all is pretty much running smoothly except the aforementioned rough warm idle and the infamous power steering groan.

When my mother took it into the local 'garage' mechanic the day after my original post, he didn't see anything wrong with it when he was test driving it around so he didn't go messing with the head gaskets or anything.

At this point I'm still eyeing the lower intake manifold being the culprit here with the rough idle and IMRC codes so one of these days im gonna have to discuss this with the neighbor, who has done work on this thing like the fuel pump/filter and the earlier mentioned thermohstat, and see if he'd be up to taking apart the upper and lower intake manifolds and at least getting the IMRC butterflies ungunked.

The one mechanic at where she works (which I honestly dont trust as far as I could theorhetically throw him. He's the one who originally wanted to throw a brand new starting system at the old 'no-crank' problem which I bandaided by nudging the car in neutral and was ultimately fixed by replacing the fairly cheap neutral safety switch) seems to think stuff like spark plugs and wires need replaced (from the way my mother is talking, he's throwing random costly ideas around for her to 'attempt'). And I keep telling her over and over that there are more cost efficient attempts to solve the problem out there. Number one being to check the lower intake manifold which is just time consuming and the cost of a new gasket.

Unfortunately I'm not a mechanic by any stretch of the word. I'm just the geek of the house who actually bothers to research this stuff online rather than relying on the opinion of the high priced mechanic. So I'm pretty much stuck hoping she doesn't go against my word and throwing money she doesn't technically have at the problem and continually trying to convince her to try these other ideas first.