I have a few symptoms that could be related, but maybe not...

This question relates to a '96 Windstar with rear heating and air conditioning.

My A/C isn't working right. There's a charge, the compressor engages, but the engine compartment cooling fan doesn't come on. The fan runs when the engine coolant reaches temperature, so the CCRM and fans are OK. When I check the high/low pressure levels, it looks OK, but it's hard to check without the cooling fans. The high pressure line gets hot, and there is some cooling at the expansion orfice, but not much.

My transmission chatters when the torque converter is locking up. This happens much more frequently, and even runs in cycles when the A/C is on. The A/C cooling is also poor even when the running at highway speed. The transmission was rebuilt last year.

I also get a misfire when I restart a hot engine after 10-15 cool down time. I'm also getting some spurious misfires while crusing at highway speeds.

Since the PCM controls the cooling fan, the TCC selenoid, and the engine spark, I'm wondering if the PCM is the ultimate problem here?

It could be EGR related as well, and I might just re-clean the EGR ports the low intake mainfold.

Any opinions?

The first thing that I would check is the radiator low speed dropping resistor.....mounted on top of the metal front bumber......you can see this when you look down behind the passenger side headlight.
You may have only high speed fans.
Mine broke.....a link to the first in a couple of pictures is here

http://rides.webshots.com/photo/2458774470011220610ybouky

OK the previous picture shows the connector.
You can get the reistor at the dealership.

The low speed radiator fans help to keep your transmission (and engine) cool in stop and go traffic.
I keep my A/C on in stop and go traffic for just the reason....the fans STAY on at low speed when the A/C is on....and the vehicle is sitting still or moving less than something like 45mph.

The low speed fans come on at a set temperature.....and then at a higher temperature the high speed fans come on.
My low speed fans did not work from when I bought my windstar up until a couple years ago.....when I replaced that ceramic body resistor.

I am not familiar at all with the rear A/C unit as I do not have one....however there have been posts about an issue with the dashboard switch for the rear unit.

For your transmission.....the first thing that I would try is a fluid exchange.....using a quality fluid that lists Mercon V on the label.


Once in a while my windstar runs a bit rough on restart when hot.

For the highway intermittent misfire.....lots of possiblilities.
So....let's start with cheap and easy......a couple cans of Berryman's B-12 Chemtool (metal can) in a tank of gasoline....to clean the fuel injectors.
Also....make sure that you are up to date on routine tune-up items.....fuel filter, spark plugs (OEM is rated at 100K miles).

Also check the hose that goes from the top of the upper intake manifold....next to the throttle body.....90 degree elbow back to the PCV valve in the rear valve cover (pre-1999 windstars).
I got a crack in the 90 degree elbow.....and also the rubber hose can soften over time and collapse when the engine is running and applying vaccum to the line.

Another potential is spark plug wires and coil pack (1 unit with 3 coils).....and EGR ports in the lower intake manifold....
The EGR ports require one to remove the upper intake manifold in order to clean.

Thanks for the suggestions.

I'll be able to tell if the resistor is actually the culprit when I finally get down and dirty and probe the CCRM voltages.

I suppose that a resolution of the inoperative cooling fans when the A/C is turned on will determine if I need a PCM, and if so, then the replacement will determine if the other symptoms in the transmission and engine misfire are due to the same root cause, or as suggested, actually independent.

Well, after checking it out, the resistor needs to be replaced. Only $80 for new one.

Now to get to the misfire... I have not done the troubleshooting yet. I'll start with a diagnostic readout and pulling the plugs. It's definately escallating though. It normally clears after a few seconds of running, but today it would not stop misfiring on the drive to work after stopping at the Ford dealership to get the resistor.

I would make sure that you are up on the routine maintenance items.
Spark plugs, spark plug wires (if they are original, they are due), fuel filter....before going to the more exotic/expensive.
Also....I have chase around a slight misfire on my '96 3.8L a couple times to find out that it was crud that had built up inside the end cap on one or more fuel injectors.
The ONLY product that I have tried that worked on this deposit is the Berryman's B-12 Chemtool.

I pulled a couple of plugs last night, from the suspected misfiring cylinders. They looked OK, but some soot (dark dry carbon) on the body (not on the ceramic). The number five wire came off with the terminal still on the plug. I re-crimped it back on to the wire.

Also, last night, before doing the above I tested to see how short a cool down period is needed to get the symptom. I shut it down, then restarted it immediately (OK). Then shut it down, waited 1 minute, and restarted with an immediate misfire. I waited 1/2 hr and restarted, and still had the misfire. I had to leave it for a few hours, but when I returned it started OK.

So far today things are OK, and after I arrived at work tried restarting it after 1 minute (OK), then 2 minutes (OK). I'll give it a more extensive check when I get home tonight.

I've used the B-12 too, and also Seafoam. They both do a good job of removing the varnish and carbon buildup from engine parts. One of my suspisions on this misfire is that the injector is leaking after it's hot, flooding the cylinder. However, I'd think it would "clear" after a few minutes of running the engine, which it used to do but doesn't anymore. However if the leak is getting worse, then it might be bad enough to maintain the "super-rich" condition. Previous codes didn't reflect that, and I didn't get them read last night. So that's an important next step...

It's definately cylinder 4, as I can pull the injector connector with no change in the engine stumble, but there's significant change when pulling cylinder 5 & 6.

Last night I checked all the potential causes that I could deal with...

I pulled the plug and ran the engine with the spark plug hanging on the exhaust manifold to observe the spark. Good spark was seen, so the coil and plug are OK. I pulled the fuel rail and manually operated the injector, and it sprayed on/off good.

I checked the rocker arm movement, and it looks good.

The EGR port was fairly clogged (close to 100%) and the other ports had signficant buildup as well, so I cleaned them all.

I drove it today with no problems, but the real check is when I can re-start during the cool down period.

The work I did on the engine seems to have eliminated the misfire. I've had no problems over the last 3 or 4 days and the CEL even turned off.

The A/C was a low charge in addition to the dropping resistor. I still have the TCC chatter. It still immediately acts up more often when the A/C is turned on.

I used my oscilloscope to check the voltage on the TCC selenoid control wire during a road test (wife driving). I can absolutely see the electrical signal change when it loses lock. However, the signal that I see is confusing to me. I expected that it would be essentially a dc voltage change (12 volts when not engaged, 1 or 2 volts when engaged), but it's actually a much more complex waveform. Even when it's fully engaged, it's not a continuous dc low voltage, but rather a pulsed wave that is high (~12 volts) for ~80 usec and low (~2 or 3 volts) for ~30 usec. I'm planning to check some of the other selonoid control lines to see what elecrical signals are present for comparison.

Does anyone know what waveform I should see? If this waveform is not normal, do you agree that it strongly points to the PCM?

I have no idea of what waveform to expect.
A good shop or dealer should be able to do a diagnostic routine.
Does the O/D light flash?.....if so, there should be a code stored.
As you already know, there are a lot of signals taking place simultaiously.....and the question is which one is causing the problem......with the others just being a result of the cause.
In other words.....the timing of the various signals is critical.....something happening (or not happening) which is followed by one or more other things taking place.

As mentioned in a couple other posts.....a TCC solenoid is one thing.....but the actual TCC is a major repair.

Don't leave out the possibility of a worn wire harness.....broken wire.....bad connection....all of which could cause the problem.
I do hope for something other than a major internal transmission repair.

Thanks... I agree this is getting into details that most DIYs are not likely to encounter.

After further research, I think the waveform is supposed to be pulsed, because the TCC solenoid is sometimes called the PWM (Pulse wave modulation). The idea is that the powertrain control computer can adjust the amount of clutch engagement by varying the percentage of time that the solenoid valve is open.

The O/D light is not flashing, but there still could be codes stored. I agree that a transmission shop could run a diagnostic with the right tool. The service manual describes the process, but it requires a electronic diagnostic tool that most of us would never have good reason to buy. The thing is, I've had this TCC chatter for years now, even prior to the transmission replacement and the initial problems I had with the rebuilt unit, so I wanted to take a stab at the diagnosis myself.

I took it the shop that did the rebuild. It was shifting hard sometimes as well as losing TCC lockup. They looked at it, measured the hydraulic pressure in the transmission, which they said was a little low. Apparently there is an adjustment screw on the EPC solenoid to change the regulated pressure. They increased the hydraulic pressure of the tranmission. I just got it back this morning, and drove it to work. It seems better, but I'll need to drive it a while to see if the problem has been fully corrected.

The problem reoccured almost immediately. I took it back and they found a problem with the TCC line on the tranmission electrical connector. This seems to have cured the shuttering issue.

However, a new one has been noticed. It seems that the TCC loses lock about 3 times a minute, very regulary. Does anyone have any ideas on this one?