Hey everyone,
I've got a 93 Aerostar with the 4.0L V-6. I've had a problem with a miss/shudder for awhile now. It misses at idle and misses/shudders really bad at speed. If I let of the gas, or put the pedal down, it mostly goes away, but at a constant throttle pressure it's really bad. The plugs (autolites), plug wires (motorcraft) and coil pack (also motorcraft) are brand new.

When I check the codes, it spits out codes for the MAF sensor (replaced/cleaned multiple times), and Lean in bank 1. I also know it's leaking oil around the backside of the lower intake, and coolant magically dissappears at a very slow rate (it's not mixing with the oil, but there's no coolant leaking to the ground.

I've pretty much determined the cause of this whole mess is the intake gasket (I figure it's probably creating a vacuum leak and causing the shuddering), but I was hoping someone might point me in another direction on the miss/shudder problem (something like a well known problem for these engines or something). I've been putting off doing the intake gasket for awhile, but maybe it's time to shrink myself in the dryer so the Aerostar can't inflict as much physical torture. Thanks.

Ian

 

If you're looking for a well known problem for these engines, the lower intake manifold gasket is certainly one of them. Oftentimes, the bolts can be tightened to solve the problem. On occasion, though, the gasket does need to be replaced. A slow coolant can be one symptom. That coolant sometimes goes into the #5 cylinder, so check that plug and see if it's fouled.
When you check the codes, which codes are you getting? Are they KOEO hard faults, continuous memory, KOER codes? Have you checked the rest of the MAF circuit? Remember that codes point to circuits and not sensors. The computer can't "see" past the end of it's proverbial nose. If it sees a fault, that fault could be anywhere between the sensor and the computer.

 

What did your old plugs look like? Agree with mrshorty, you ought to monitor your plugs as a way to try and isolate the miss to a certain cylinder. My own experience with disappearing coolant/bad intake gasket on my 4.0L suggests you ought to pay particular attention to the #4 cylinder, as well. As noted, re-torquing the intake manifold bolts is something you can try.

On the other hand, running lean on Bank 1 would suggest a vacuum leak of some sort on the other side of the engine (cylinders 1, 2 & 3). A leaky upper intake gasket can allow in unmetered air, too.

How do all your vacuum hoses look? PCV valve is new and snug?

A problem with fuel delivery (clogged injectors, for example) can also cause a lean condition.

 

Thanks for the quick replies. I forgot to mention that I did pull the plugs the other day, and #5 was fouled. I cleaned it up, and put it back in with no change in symtoms. Also, all of the vacuum lines that I could see were in good shape, but it's tough to see anything in the engine bay of an Aerostar. lol.

I've managed to put off some projects in work and will be doing both upper and lower intake gaskets tomarrow. Reguardless of whether it's creating the shuddering problem, it is leaking oil and loosing coolant, so it needs to be done anyway. I'll report back as to whether or not the shuddering goes away. Thanks a lot guys.

Ian

 

I"ve got the same thing going on with my 99 ranger 4.0. .133500 miles. . .I check the #4 cylinder today and the plug was fouled bad. . all the rest of the plugs looked pefect. The #4 plug was also rusted some, and the threads on the plug hole were galled a little. . .could this be from the intake gasket or from the head gasket? Similar problem, but maybe different source? It's been missing off and on for a while now, started to be noticably down on power a couple days ago. Any opinions?

 

It does sound like a gasket issue, as to whether it's an intake or head gasket, more info is needed, such as: Any white, lingering smoke out of tail pipe, especially when warming up after cold start? Overheating concerns? Other symptoms of a blown headgasket? If not, odds are it's a lower intake gasket, based on the history of the 4.0L OHV. Your Ranger is just about at the same mileage as mine was when I had to undertake the repair:

https://www.ford-trucks.com/forums/s...d.php?t=232373

P.S. Welcome to FTE!

 

Thanks for the quick reply Rockledge. . .

As for other symptoms: I don't have any smoke at startup, or any other time, and I've never had any over-heating problems. The main thing is that I've noticed I've slowly been losing coolant from the resivoir, and have to fill it up about once a month. Then this week, it started missing something fierce, and it was the #4 plug. So, from what I've been reading from y'alls experience, looks like i'm going to look at putting in a new lower intake gasket this weekend.

Once again, thanks for all the help. . .I've found more good information here than I've found anywhere else.

 

Well, I never did get around to doing this yet. My life has been very topsy-turvy lately. I will be doing it this week though, and report back. Thanks again for everyone's input on this. I really appreciate it.

 

Well, after 12 hours (over two days) and a blood transfusion due to having my arms skinned while working on this thing, it still has the shudder/miss, although not nearly as bad. Now that the intake gaskets aren't leaking, what else could cause a problem like this? The problem only presents inself when in overdrive. Since completing the intake gasket job, it's been driven for about an hour or so and no codes have been set yet.

Here's a list of new parts so far...MAF sensor, coil pack, plug wires, plugs, upper and lower intake gaskets (along with valve cover gaskets since they have to be done at the same time), and PVC valve. My dad thinks it's a bad fuel injector. I tend to disagree though, because the problem would be more evident in a higher RPM than while cruising in OD.

At this point, I'm totally frustrated with this van. I've never had such a hard time trying to fix a vehicle before, and after going through the torture of replacing the intake gaskets and having the problem persist, I'm very disheartened. The intake gasket was a definate problem since the vehicle does run much better now, and the gasket was all fubar'd when I pulled it off (the rear of it was all torn up, and I could see where coolant was coming from the front coolant port and working it's way to #5 cylinder), so I'm glad that those problems are fixed, but it's killing me that the problem is still there.

 

Did you ever replace the O2 sensor? Mine went bad on my 93 Aerostar at about 65,000 miles. That would give also explain the code you got.

Good luck

 

I experienced the same problem that you had with a 93 aerostar 4.0 liter: Rough idle and shuddering at constant speed. The shuddering disappeared under acceleration or deceleration. Also new plugs and wires did not solve the problem. The #2 plug had detonated(tip was missing). I took it to the dealer for an autopsy and they checked the compression on all 6 cylinders. #2 cylinder had about 20 lbs compression. The dealer quoted a price of a new engine and I did not pursue fixing the problem. I found a '91 aerostar with 80,000 original miles for cheaper than the price of an engine replacement.

 

Coolant will mess up O2 sensers makeing it run rough. I replaced one on my wife's 98 Explorer. It was green from coolant. It runs like a bear now. (dealer replaced intake gaskets- thank goodness my wife wanted extended warranty)