99 F-150 w/ 4.2L 4x2 std 5 spd trans.

Symptoms;
I was in line at a drive thru when the engine almost died. I started hearing something like a tappet noise and it would barely run. It would not die but it was running very badly with the "Service Engine Soon" (SES) light flashing.

Starting to Diagnose;
I stopped by an autoparts place and borrowed a code tool since my was at home. The codes were; lean mix, misfire cylinders 1,4,5,& 6. There wasn't much that I could do there in the parking lot, but I did replace the fuel filter in thanks to the counter people. The filter did not have too much restriction.

I did not have any choice since I had to get back home. So, I drove it the 40 freeway miles back to my home. The SES would intermittently flash then steady on. At home, I pulled the same codes. I verified good fuel pressure. Then, pulled the plugs - the right bank (cyl 4, 5, & 6?) was extremely sooty. I had one of my girls crank the engine. It did not appear that there was any compression on cylinders 4, 5, & 6.

Initial thoughts;
I thought that this might be a simple timing chain r&r. After disassembling the front of the engine, I finally removed the CMP. I looked in there and found that the camshaft sprocket is metal and not plastic like I was expecting.

History;
I replaced the Synchronizer (bad bushings caused the hall effect vane to rip off) about 2 years ago. About 3 months ago I had to solder chewed wiring at the ECM (a mouse tried to make a nest of the wiring).

I am at work right now, but I am off the next couple of days to work on this problem.

Does anybody have any other thoughts?

 

Hi and welcome to the forum

How many miles on the truck? How many on the spark plugs?
Does it use any coolant or oil?
The 4.2s suffer from leaking intake manifold gaskets which can allow coolant into the cylinders. They run really bad when that happens. You have to remove the intake to see the leak. The gasket spits out in between the coolant passages and intake ports.
Do you have a compression tester that you can check the dead holes with?

 

With it making that noise I would make sure you havent thrown a rod...it could be that you have and now its bouncing around in there. Could also be a problem like you said w /the timing chain..hard to tell w/o being there.
-Chris
PS Welcome to the site..you might want to ask this down in the engine specific forums...may be a little more help down there

 

It sounds like you more than likely have a broken valve spring. these motors are prone to valve spring failures. It happened to mine in just the way you described.

 

Gosh, I hope that it isn't a thrown rod.

The engine only has 139,999 miles on it. The plugs were changed at approx 125k miles. The oil appears to be ok, no indication of coolant in the crankcase. I couldn't find my compression tester, I figured a finger stuffed in the spark plug hole would tell me if there was any compression.

Now that I am off today, I guess I'll have to; get another compression tester and get a good wet/dry reading, pull the oil pan to finish getting the timing case removed.

At least there is room in the engine compartment now so that I can stand in there if it starts to rain.

 

Do the compression test. You will find that you have a broken valve spring. The compression leaks back into the manifold and gives you the misfire on the other cylinders. I have been in the same place that you are.

 

Would a broken valve spring on this motor also cause poor braking due to low vaccum from the compression coming back into the intake? I am experiencing this same valvetrain rattling noise and I have next to no brake boost. Its definitely not bottom end knock. It sounds like either a broken valve spring, bent vavle, badly bent pushrod, or collapsed lifter.

 

It must have just been a coincidence that the cylinder I initially checked compression is the one with the busted valve spring. Yes, just like the later posts suggested the #5 cylinder had a broken intake valve spring.

I did not notice any detrimental effects on braking when I drove it home.

I yanked the heads and found a good machinist. He had examples of connecting rods broken due to the coolant leaking into the cyl. Just standard work needed to be done to the head and valves. Thank goodness

Over the last couple of weeks I have been working on it off and on. I only have a couple hours a week that could devote to repair. But, I am almost finished. I should have the truck back on the road tomorrow.

The only concern that I have is that I have to eyeball the CMP in place. Confidence is not too high that I have set correctly. Wish I could find the tool.

 

Mine turned out to be a broken exhaust valve spring on number #5 - I believe its number 5 (pass. side middle cylinder). I replaced the spring for $4.88 from Ford and installed a new valve stem seal at the same time since the other one got beat up a tad. The truck fired right up and has driven fine ever since. Braking is perfect now also.