Well, I finally almost got bit. Here's how it happened.....
Drove about 300 miles to a job site yesterday afternoon. I went in and worked for about 5 hours.
When I got back in my truck to crank it, it turned over about 1-2 seconds and then did the major "blow-back" thing. You know the big "huff, whoosh, belch" sound a lot like you used to get on a cold morning when you'd have blow-back thru the carb.
I have had this happen a few times before, although not as bad as last night.
Not thinking too much about it, I turned the key again and the truck started. Then, things went south.....

I knew the sound immediately: rod knock. Plus it was running like it was only firing on 4 or 5 cylinders. I shut it off after 3 or 4 seconds, and sat there thinking "Well, I just got burned."

Not having much choice I started it again and let it knock, just to see what would happen. After 5 or 10 seconds the knock went away, but it still idled real rough. So, I let it idle for a minute or so, it smoothed out and I revved the motor some. All appeared OK. I was relieved, but a little concerned, but I hit the road.
Approx 210 miles later, I pulled in at a hotel and shut it off, hoping for the best the next morning.

This morning I held my breath and started it. No knock, but it did idle real rough again. After a minute or so the CEL came on as the idle began to smooth out. Once again, I hit the road and (aside from the CEL on) all was fine. Ran as smooth as it ever did.

When I got to Bham, I pulled into an Advance Auto and asked them to check the OBD II code. I told him I expect a cylinder misfire on #2.
Guess what it was...
Cylinder misfire on #2.

I am set to drop it off this afternoon for an intake manifold gasket replacement. $325 is what they quoted.

Here's my theory:

As the truck sat idle, the #2 cylinder was on just beginning the power (down) stroke, and some liquid had leaked into the cylinder.
The #2 piston went thru the power stroke, then thru the exhaust stroke (blowing most of the liquid out thru the exhaust valve). The piston the went thru the intake stroke, got its fuel/air charge and then started the compression stroke with a little liquid remaining in the cylinder.
This is when the huff occured.
After restarting, the cylinder was able to expel the liquid, with the consequence being short lived rod knock and a fouled plug.

So, that is where I am right now. I got lucky - real lucky. Aside from the CEL being on, the engine runs smooth. So, I'm going to thank my lucky starts and get it repaired. $325 would make me happy if that is all it costs!

 

Jeez Brian, I didnt think you walked the wild life? Haha. Glad to hear its all good. Is this on the 05? Or, do you still have the other 4.2? Good luck.

Garrett

 

Garrett,
This is the 2000. It now is at 157,000 miles.

 

Brian, just curious. How often did you change the coolent? I have been flushing and putting in new coolent every other year in my 99. LAst change was April 04 at 73000. I have 81,000 on it now.
Dan

 

probably average a rad drain and refill about every 30,000 miles. I had to have the radiator removed and cleaned out last spring, so the system got a complete flush and refill back then.
I don't think the coolant replacement cycle had an impact on this event.

I'm just resigned to accept that the fly in the ointment for the 4.2 is the intake manifold gaskets.

Given the correction of the early run problems with premature failure (70-80-90,000 miles) I'm inclined to believe that as the engines with the new and improved gaskets get high miles on them, that the intake manifold gasket is the first major (and so far the only major) issue to crop up.

Given that it appears I didn't do damage, I'd rather deal with this than replacing an automatic transmission, or some other more $izeable problem.

 

Glad no major damage was done. coolent changes prob. not the cause, as you said. I think my intake is allum? So there should not be a acid effect between the intake and head.

 

Brian, did you get the head gasket fixed?? The head gasket can leak into the cylinder also. I may have missed something, but in our last conversation on the phone, you said that the head gasket was blown. This could easily leak into the cylinder and cause the same problem. I had the same thing happen on a nissan. If you fixed it, then you may be right, but if not it's the head gasket, not the intake seals.

 

Thomas,
I talked to the guy at a local independant shop. He was familiar with the problem and actually had another 4.2 in at the time. He said it is almost always the lower intake manifold gasket - so I went with that. I am to assume that if the intake gets pulled and the gasket is OK, he'll call me for the OK to go further.
As a side note, he said he has replaced bent rods on a few motors and once done, the motors are good-to-go.
He also said he can install a new Ford crate motor for $3,100. 3 year/36,000 warranty. I didn't think that was too bad - but hope I never face it!
I'll let you guys know the outcome when I get the truck back.

 

Man that stinks. Say, if you have to go crate motor, are you gonna consider, a slightly "stronger" motor, like from rpm mustangs with a small torque cam? I really hope that it's not needed, and I know you will keep us posted.

 

UPDATE:
I just called the shop to satisfy my curiosity.
He told me everything I had speculated was exactly what they had found: lower intake manifold gasket, slight leak into #2 cylinder.
He said they ran a compression check and all cylinders look good.
In short, I got lucky. Nothing was damaged. Everything should be fine.

I plan to pick it up tomorrow.

I am grateful that I got lucky and realize others might not be so fortunate.
Asusming it is no more than the $325 quoted, I'll be very happy.

One of the main keys to all this was noticing a slight coolant drop and pulling the plugs to find #2 slightly discolored.
It was my own delays that really put me more at risk.

So, high mileage 4.2 owners - check your coolant level every week or two. OR proactively replace your intake manifold gaskets whenever you stop feeling lucky!

 

Great that the fix was some what simple. Did they give a probable reason for the failure? Any thing that can be done to prevent this?
Thanks Dan

 

No specific reason given. I think it is just the nature of the beast.
Seems many engines have an Achille's heel.

I don't think there is anything to prevent it and I don't think it likely to occur on every single 4.2 out there.

The 4.6 and 5.4 motors have had problems with piston slap, spark plugs blowing out, and other stuff ???

I don't feel so bad really. Hey, I bought a brand new '05 with the 4.2 AFTER I knew I had a leaky gasket on the 2000!

 

UPDATE:
Picked up the truck today.
Everything is fine and it runs good.
They replaced the gaskets, replaced the thermostat, replaced the PCV valve and hoses to it, replaced the bad #2 plug, had the inside of the intake bead blasted (to remove built up crud) and added new coolant.
Total price = $402.
That is a GOOD deal in my book!

It does run better. I'm guessing there was slight, progressive loss of performance over time due to intake getting cruded up.

It is more "responsive" and the slight ping is gone.

I'm a happy camper!

 

Great, hows the 05 doin? Any pics yet?
Dan

 

Great!
Nope.