Hey Guys,

I've hit a road block with my Aerostar...

Current Situation:
When I start the van in the morning, no problems. Starts up runs great.
About 5 minutes later when I come to a stop, the engine is lightly shaking and I get codes P0303 and P0305 (miss fire cylinder 3 and 5).
Proceeding from a stop, the engine clears up and it feels better.

Repair Attempts:
New Spark Plugs, Wires, Coil Pack
New Fuel Injectors (new gasket under the fuel rail and plenum gaskets)
New Fuel Pressure Regulator
New Engine Coolant Temperature Sensor

Readings from the Mass Airflow Sensor and Intake Temperature Sensor are normal.

Does anyone have any other ideas?

 

ECU ?? Its stressfull when problems like that come up

 

Lots of things can cause miss fire. Have you checked the crank or cam position sensors?

 

which spark plugs did you use? The 4 liter eats spark plugs like crazy, ask me how I know. The symptoms are always a peculiar missing under acceleration, like an electrical miss.

In my '97 4.0 it's always a spark plug. Find the bad one, and problem is gone.

 

All,

I used NGK 3403 G-Power → https://www.rockauto.com/en/moreinfo...105209&jsn=492
Just bought some of the Autolite AP103 (as I saw in this post courtesy of Jose A.)

Next Steps:
1) Disconnect and plug EGR tube → Check Condition
Condition No Good?
2) Replace all spark plugs with Autolite AP103 plugs → Check Condition
Condition No Good?
3) Compression check all 6 cylinders → Check Condition
Condition No Good?
4) Roll Ford Aerostar into the Kalamazoo River (just kidding!)

It's hard for me to believe it is the spark plugs since the running condition improves under load.
But after reading the post mentioned above, I guess it's worth a shot.

 

Autolite sent me AP103, APP103, IRRIDIUM 103, and the only ones I didn't get were the Kryptonite 103.

The AP103 are the only ones that last longer. In all the others the ceramic insulation cracks after a while and the missing starts all over.

Also check your battery cables at both ends, and at the Start Lock Relay, a loose cable will cause intermittent misfires.

 

Most likely lean running at warm idle. common in these.

Leaking vacuum lines, lots of little tubes running everywhere. check the fuel vapor cannister and assorted vac solenoids tubes under the air filter box and the long stiff vacuum tube to the throttle body.

change the O2 sensor. won't help if poisoned by coolant leak >head

idle air control on side of TB worn and dirty.

dirty MAF, runs on MAF control when warmed up.

OR
the drive it off a bluff failure.
leaking valley coolant gasket/head gasket, sucking coolant into intake manifold. poisons plugs O2 sensor and CAT. not as common on the '97 only Aero with the new head design heart shape comb. chamber fast burn with different fueling map in PCM

the 4L OHV uses the Ford wasted spark ignition system, requires double platinum or double iridium plugs. Autolite last the longest by far.
https://www.fordforumsonline.com/threads/dis-edis-ignition-systems.265/

Rebuilding The Ford 4.0L Pushrod V6 - Engine Builder Magazine

https://www.fordforumsonline.com/for...eline-axle.70/
are your knuckles and arms still bleeding after all that work under an Aero hood?

 

I think the reason why you are eating plugs is because you are running too cold of a plug. The (x)103 is the coldest plug in that size (according to the autolite heat range guide), and factory calls for a SP486 which crosses over to a (x)605 autolite plug which is the hottest plug in that size.

I was running APP103's and they started fouling out badly, I switched to APP605's and so far no hesitation or miss.

I am thinking that the 103's are way too cold for the 97 4.0L and that is causing the issues we are seeing here.

Here are pictures of the plugs I pulled, the one at the top was only in for 6 months.

https://cimg8.ibsrv.net/gimg/www.for...fd4e7830b3.jpg

 

93nighthawk,
thanks for the information, I will try the 605. However.the factory Label under the hood says to use AP103.

 

Yes, thats what it says, but its wrong for two reasons, one, the AP103 is only good for one side of the engine, you'd need an APP103, secondly the specs on those plugs have changed since then. The requirements according to Ford changed over the years too as they realized their original recommendation was incorrect. The 4.0L were prone to carbon build up (in part due to too cold a plug), and this build up would cause pinging. By using a hotter plug it helped prevent the build up.

 

was not aware of this, Khan.
so on which side should I use the double platinum APP103 ? Driver or passenger side?

 

The double platinum plugs can be used on either side. The waste spark EDIS of the 4.9L engine uses a single coil to power two plugs, one on each end of the coil. So it sends current in one direction to the plugs on one side and the other direction to the plugs on the other. If you use the single platinum plugs long enough, you can see the wear on the ground electrode on one side. You MAY be able to get the plugs with the platinum tip on the ground electrode from your Ford parts dealer, but it may cost a lot. It's cheaper to get the double platinum plugs, and you may eventually see the different wear patterns on each side, but they should be a lot less than on non-platinum plugs.

 

ok, but my Aerostar has a 4.0 liter, not a 4.9 liter, or was that a typo?

 

Sorry, that should have been 4.0L v6. But it would apply to any engine where they use and EDIS with 1/2 the number of coils as spark plug count.

 

When I started having Similar Problems, I discovered that a Vacuum Cap, on the Back of the air horn was Blown out...From the Front, you can reach in on the Right Side and reach right around the back and feel the little vac. nipple...The High Heat seems to Cook the Rubber Pretty Quick ....
2nd.... Touching the Throttle at Start Up, will cause a Back fire in the Intake and blow the cap off.... so Missing after an engine warms up.... Points to a Vac. Leak.... the Cap, Was Blown off... I keep an assortment of Vac. caps, under the seat...
If you pull the Dog House.... from inside, you can see the vac port on the Left side... from the Drivers side....