I have a 96 Windstar with a 3.8 litre V-6 that has an engine checklight on. My AutoTap diagnostic software indicates that the checklight was triggered by excessive missfiring of the #4 cylinder. No other cylinder missfires are reported. The miss is noticable but intermittant. The engine does not seem to miss during cold startup but develops after the engine is warm.

I've replaced all the sparkplugs and also the sparkplug wires with no improvement. I just checked the compression and #4 reads 130 psi, the same as #5 and #6. I'd considered replacing the coil pack as I was out of electrical options. But then I learned that there are actually only three coils in the pack with each firing two cylinders. Since AutoTap does not report misses on other cylinders, I'm now assuming the coilpack is not the problem.

I'm now at a loss. Any suggestions?

 

Dave , Where any other codes set ? Has the van recently run out of fuel ? I know its unlikely but the pinpoint test asks if the vehicle has recently run out of fuel

 

No other codes were set. I've flushed the codes and turned off the checklight several times with the same result. The engine begins to missfire (this an obvious miss but not so bad that the vehicle is undrivable) then the checklight comes on. There are always three or four error messages that all indicate missfire on #4. I also used a stethyscope to listen to the injectors thump. I couldn't tell that #4 was any different than the other.

How does the engine computer know the missfire is with #4? Could it misidentify the bad cylinder?

My understanding is that the coil pack fires both #4 and #3 at the same time - but that #3 is on exhaust stroke so the spark doesn't do anything. I assume that I could just switch the #4 and #3 leads at the coil pack to check for a problem with the terminal connections?

Are there any other electronic components that could cause a missfire on only one cylinder?

Any help appreciated.

 

Post the codes you are gettting .

 

The code is:

P0304 - Cylinder #4 misfire detected.

I got that repeated 4 times.

Also, just before the last test, I switched the #4 and #3 sparkplug terminals at the coil pack and got the same error as before (#4). So I'm confident the problem is not the coil.

Is there some way to electronically check individual injectors?

Thanks,

 

i guarantee you your intake gaskets are leaking. ford has updated these gasdkets with a new design. cylinders #1 and 4 are right next to water jackets. what happens is the gasket fails right between the intake and coolant ports. it lets coolant into the combustion chamber after the vehicle is under pressure. but only in small amounts. after you shut the vehicle off from a drive the pressure in the cooling system bleeds into the intake port. then when you start the vehicle later on coolant is in the combustion chamber and you get a misfire for a little while until the coolant burns away. this is why it is an intermittent misfire. one morning after the vehicle has sat overnite pull the #4 plug out after running the vehicle for about 3 seconds whern the misfire is present. if the plug is wet with coolant then that is your problem.

 

the pcm knows what cylinder is misfiring because it see a rmp drop from the dead cylinder. the pip (crank) sensor sees the crank shaft speed and when no 4 misses the rpms drop. it uses the crank sensor to identify the rpms and always knows the position of the #1 cyl. and knowing where # 1 is it also now knows when # 4 should be firing in relation to rpm. kinda hard to explain.

 

The symptoms are that it seems to run fine when cold but begins to miss after it warms up. That's not what I would have expected of a leaking intake gasket - but I'll try finding a vacuum port tomorrow and take a look.

The engine seems to run strong except when it's missing so I sort of thought it didn't seem like a mechanical problem. Also, I have no oil in the coolant, coolant level is good, and no water in the oil.

Does the 3.8 have a wet or dry intake?

Thanks,

 

I'd forgotten to mention in reply to one of the earlier querries that no, the vehicle has never been run out of gas.

 

That was me that asked about running out of fuel ... My next question was going to be aimed at the intake manifold gaskets , Ford has had lots of troubles with a lot of different aspects of the Windstar vans , There are even hate groups on the net devoted to Windstar vans . When I looked at the pinpoint test for code PO304 it listed most of what you checked plus the running out of fuel section , Sorry I cant be of more help .

 

Well, I hooked up a vacuum gauge and the manifold vacuum is very steady at 17 inches - even when the engine is missing. Under gentle throttle it rises to around 28 and drops to near zero under sudden full throttle. Looks pretty normal to me and not what I'd expect for a leaking intake.

I also pulled out front bank spark plugs after the engine was warm and missing and couldn't see any indication of moisture. The plug surfaces look nice and tan suggesting a nice burn.

Someone mentioned that blown intake gaskets were extremely common on 3.8 engines. If the odds are that the problem is the intake gasket in spite off no diagnostic support, then maybe I should go ahead and change it out. But I'm still nervous that it's some sort of electronic glitch.

Does anyone know of a Windstar specific support group?

Thanks for all the help and suggestions.

 

you wont see any weird vacuum readings on a gauge. it will appear perfectly normal. and for the head gaskets, true the older 3.8's were terrible but 96 and up uses the split port engine. the head gaskets on these are of the steel shim and bonded plactic type and they do not blow. that is not your problem.

 

 

Just to finish off the thread:

I finally got around to replacing the intake manifold gasket over the weekend. So far the engine runs like a champ. After about 50 miles so far, the check light has not come on and there are no dectectable misses. I think we got it.

I'll admit that I was skeptical that the problem was the intake manifold gasket. I was even more concerned that it was something else when I tore it down and looked at the original gasket. There were no obvious spots where fluid was moving past the seals. And my old coolant was very dark colored. At first I was afraid oil was blowing oil into the coolant (head gasket or worse) so I poured the goop into a clear container to see if oil settled out. No fluid segregation. I guess it was just polluted with combustion stuff from the intake leak.

Thanks for the help/diagnosis. I would not have guessed the intake gasket was the problem from the symptoms - at least not until it got much worse.

Dave Bell

 

I have a 96 Winstar GL with 3.8 L V6 with 85K miles. The engine sometimes misfires after it starts in the morning, after long drive breaks, or after sitting in an airport lot for a few days. The engine would run rough and the check-engine light would blink.

After fixing a vaccuum leak, clearing out the exhaust recirculation ports and replacing an idle valve on top of the engine it runs great and gets 22 mpg hwy!

Occasionally however it still misfires on a start-up. I accidentally discovered that an immediate shutdown, pause and restart cleared the condition (much to my relief a few times). I would drive it hundreds of miles in between such problems just fine but with the engine light on steadily. After a few hundred miles the engine light would go out.

A mechanic friend who has been helping me is puzzled but believes that eventually it will get worse and I will be stuck. It has been 6000 miles now and about 5 months (since my wife basically swapped cars with me) and except for the occasional startup issue the engine runs great.

There is an OBD Case Study 8 from Colorado State Univ. which basically states that the misfire codes are occasionally erroneous and that the dealer can reprogram the PCM according to one of their TSB's. The problem I am having is a little different because my engine is really running rough when the light comes on until I shutdown and restart then it acts like nothing happened. It's almost like resetting a computer.

Is this the same problem like you have been talking about but in a different disguise? Any suggestions? I tend to believe my mechanic that I am running on luck for now but it it runs so well most of the time and I do not want to throw money at it. Your thread has been very helpful and encouraging.

Thanks