New coil; still missing/bucking; '99 3.8L

[serge_saati]

Originally Posted by Windywoes

Second, and pardon my ignorance, isn't the battery voltage the same as alternator output when the van is running? In other words, when the van is running isn't my battery output adequate to run the PCM? To me, 11.7 volts resting seems awfully low. I measured all my other cars and they ranged from 12.4 to 12.8 at rest.

Yes, sure...the alternator supply all the electric devices with enough power.
What I meant is if it's a bad contact on the battery terminal, the alternator's regulator could arc high voltage at output and damage the PCM. Cause the regulator is made with inductive coil and give more voltage when resistance increase. V=R*I

[Windywoes]

I checked the back three plugs and they look fine. Also looked more intently for possible vacuum leaks. The only issue I saw was a very loose interface between a large diameter hose going from the rear of the throttle body to a climate control valve. I put a clamp on one end of the hose.

What do you think about the possibility of the cat converter clogging?

[serge_saati]

Originally Posted by Windywoes

What do you think about the possibility of the cat converter clogging?

This is very rare. If it was the case, your engine will run very roughly at idle.

If you run with O/D off on an up hill, is it buck/miss?

[Windywoes]

Yeah, I doubt it is the cat. The acceleration is very strong and it idles smooth.

Sometimes it will buck even when the O/D is switched off while going uphill. It will buck in 3rd or 4th gear.

Just drove it quite a while after clamping the vacuum hose and I could not make it buck in the usual hilly places around town. Tomorrow I am off to VT. That will be the ultimate test: lots of hills and six people in the van.

[fords4me]

It may be the fuel pressure regulator, pull the vacuum hose off of it and if raw fuel spills out, the regulator is bad. My mustang would buck at low speed and the idle would surge and sometimes stall when I was stopped. I would also check the IAC(Idle Air Control Valve) if your winny has one, I almost certain it does.

[Windywoes]

Good suggestion. First I need to locate this device as I am not familiar with it. Is that test while running or not running?

I cleaned the IAC just a short time ago. Seems to idle very smoothly.

[Windywoes]

No fuel is spurting out of the top of the fuel pressure regulator vacuum port while running or at rest. The U-shaped vacuum line and rubber boots are in very good condition; no cracks or holes that I could see.

[serge_saati]

Originally Posted by Windywoes

Tomorrow I am off to VT. That will be the ultimate test: lots of hills and six people in the van.

Let the trans cool down sometime, if not, you may break it. Always climb in 3rd.

When I travel with my Winny, I avoid up hill most as possible. It must be the reason why my trans keep that long. I check the altitude with map 3D to find the best roads.

[Windywoes]

Sort of unavoidable tomorrow as my relatives live in a mountainous area. I try not to hammer the old girl though.

[wiswind]

The driving in "3rd" is accomplished by pressing the O/D button to disable the O/D.
You want to do this when you find your transmission shifting between gears.
It is when it is shifting that it generates the most heat.
When going up steep hills....it is not uncommon for the transmission to seem to "hunt" shifting up and down.......this is what you want to avoid.

Avoiding hills is not an option in certain parts of the country.
Some places.....if you are not going uphill......then you must be going downhill.
Interstate highways tend to be less intense with the hills.

[Windywoes]

Yup, I used the O/D button a lot yesterday.

[bkimbel]

I recently had a similar set of symptoms with the almost missing and bucking as I went up hills.

I wound up replacing the IAC, and the symptoms appear to have disappeared. About a thousand miles and counting so far.

BK

[bkimbel]

Possible solution!!!

I had my Windstar in for the 288K checkup today, and the mechanic test drove it to see about the bucking I was also experiencing.

He recommended that I visit the transmission repair shop where I had the transmission rebuilt about 50K miles ago.

So I did. We went for a ride around his "test track", in-town driving, with the bucking coming back on almost every slight uphill grade. He asked about whether the fluid is the same as when they rebuilt the transmission, and I told him the story of getting the oil pan punctured.

We got back to his shop, and he poured in a 6 oz (or so) bottle of Motorcraft Friction Modifier, which he also referred to as that "stinky" additive. (It was enough to gag a gnu through the lid and the seal!)

After driving about 15 miles, with NO more shuddering, I have the following to report:

The problem is related to the Torque Converter. The addition of the Friction Modifier appears to have resolved THAT problem!

I am cautiously optimistic...

By the way, the transmission guy says that Ford recommends this to resolve this problem.

Hope it keeps working! I'll report back if I have a recurrence of the problem.

BK