Repair or Replace?

1998 F150

201,054 miles

4.6L Engine

4R70W Transaxle

Check engine skip – no MIL

Driving a vehicle and expecting things to go well is one thing, but when repairs are necessary, the customer calls the shots, but we have to guide them to make decisions that are right for them.  To begin with, we have to determine as nearly as possible what they expect to get out of an aging vehicle after the repairs are done.  Will they be making long trips or pulling heavy trailers or will they just be puttering it around town on the weekend?

First we have to find out what’s the problem is, and that’s where it all started on this F150.


Coming Back for More

When customers have a good experience at a shop, they generally return to that shop. This customer was no exception.  We have worked on her vehicles for awhile, and this particular truck was one we had replaced the wires and spark plugs on a few months back.  She came to ask if she could bring it to us and I gave her the green light.

When the truck arrived and the paperwork was done, it had a P0305 code and a dead skip, but no MIL at all.  Upon hearing this report from my guys, I sat in the seat and switched the ignition on to find that the MIL was inoperative. That dark and dead MIL would need fixing to be sure, but it wasn’t our primary concern.  Number five was a dead hole, but the injector was clicking, spark was present, and the spark plug didn’t look greasy. With the obvious out of the way, it was time put on our detective hats. When Webb and Kelley came into my office and put the known facts on the whiteboard, I put on my Horatio Caine “CSI Service Bay” sunglasses and said,

“Okay, this is what I want you to do.  Get a compression gauge screwed into that hole and let’s see how far that Number Five will push the needle. Spin the starter through for at least six puffs.”  As I heard them cranking the engine over, it was obvious to my practiced ear that the crank was picking up speed during one of the eight compression strokes, and I knew which one it was.  But the cause of the dead cylinder had to be further pinpointed, and we needed more data to complete our forensics.

After the six puffs the needle pointed to seventy pounds of compression. Their questioning glances said “What now?”  The next logical step was a no-brainer.

“Now,” I told them, “we find TDC compression stroke on that cylinder and do a cylinder leakage test.”

There are a number of ways to do this on a cylinder that has any compression at all and it’s especially easy when the cylinder in question is the number one hole or its companion, but what about the unmarked cylinders?

Since we have an IPA Tools® Calibration and Set Up kit (#7891), finding TDC is a snap on just about any cylinder.  First we screwed the IPA whistle adapter into the spark plug hole and the 70 psi of compression that piston was pushing was plenty enough to make the whistle tweet as the cylinder was coming up with valves closed. That got us on the right stroke, but we needed to TDC that piston else the air we were about to apply during the cylinder leakage test might blow it back down, driving the train to open a valve and invalidate our test.

To bring number five to exactly TDC, we applied the dandy spring-loaded IPA® TDC finder and brought the piston squarely to the top of its travel. With those tools put away, we did a cylinder leakage test and found just under 70% cylinder leakage – it should have been a lot less than that, and now we had two rock-solid bits of data – three if you count the DTC.  Now we needed to see where that leakage was going.

“Okay, guys, ordinarily we’d do some listening exercises with the air flowing through the leakage tester, but why don’t we apply smoke to that cylinder and see where it makes its exit?”

With the throttle propped wide and the smoke flowing through the leakage tester hose into the chamber, we saw smoke immediately came wafting out of the throttle body.  We obviously had an intake valve that was compromised for some reason, and I’d need to talk to the customer about this one.  If the intake valve had been totally open – 100 percent leakage – exploratory surgery might have been in order to check for a broken valve spring. As it was, this head would seem to be a candidate for a valve job, and that’s a pricey repair on a 200,000 mile 4.6L! Timing chain kits, gaskets and everything would put this repair estimate in the stratosphere.  A used engine might be in order if they weren’t planning on using the truck for another 20 years, and I called LKQ, who priced me a used one for $650.  I put left the F150 in a holding pattern and left a message for the owner to call me.

Dribbling Green


We had replaced the radiator and repaired the A/C in a 2003 Chrysler 300 at about the same time we did the plugs and wires on the troubled F150, and now the 300 had pushed its temp needle high again but for a different reason.  We also had a transmission swap under way on a 2002 PT Cruiser and would need to check that one for an overheating problem too, but that’d happen when we were through with the trans swap.  I had a couple of guys working on the PT, but I re-assigned the guy who was assisting with the Cruiser and had him tackle the 300, which, when we pressure tested it, turned out to have coolant leaking in a thin stream from behind the balancer.  This one would need a water pump and a timing belt.  Had this been a Sebring with a 2.7L in it, we would have shed tears, but this 300 isn’t that tough to deal with, and Garrett needed to do a timing chain and a water pump anyway.

Meanwhile, Braxton and Joe jerked a 98 Crown Vickie police package trainer vehicle into a service bay and began the process of removing the engine as a worksheet assignment.

We also troubleshot a 2007 Altima with a delayed reaction blower motor issue – she’d start the car and for five minutes the blower was inoperative, then it would come on line. We duplicated that concern quite easily, did some voltage checks at the fuses, and after we transposed the blower and defog relays, the problem went away. I ordered a replacement relay ($30) but it’s still lying on my desk – a delayed defogger just isn’t as noticeable as a windless fan. I’m still foggy about how a relay can cause that problem.

Speaking of fans, a guy came in with a Mustang that day because he wanted us to replace his cooling fan motor, which was fresh fried and stinking.  The reason for the fried fan was an distorted shroud, which had fouled the fan and kept it from turning until the windings were cooked. We had to explain that he needed every part of the fan, not just the motor, and more money would need to change hands to make that happen, but the bill wasn’t too bad. Back to the 300, since Garrett had to jerk the fan and radiator to access the timing cover properly, we decided to check the cooling fan motor for open commutator segments, because a bad fan can be famously intermittent, and it’s smart to do that.


The Dirty Hand is Dealt


The F150 owner called back and opted for the used LKQ powerplant, and the real adventure began.

Replacing the engine in a 1998 F-150 isn’t for the lazy, wimpy, or faint-hearted, and that’s why I gave the job to Willie, who is a Viet Nam veteran, older than I am, and tough as nails. Well, Willie got the engine installed, but not before we had to buy a $30.00 eight bolt flywheel from a local salvage yard because the original engine had a 6 hole crankshaft and the original flywheel wouldn’t fit. I had called LKQ and they verified that the vehicle in question could have either a 6 or an 8 bolt crank on a Romeo 4.6L, but it would be several days before he could get us the right flywheel, so we patronized the local salvage yard in the interest of time. What naiveté!

When the replacement engine was in place, we found it spinning with almost no compression along with intermittent backfiring through the intake. After checking and re-checking the spark plug wire routing, we measured the compression and found one cylinder with 99 psi and 40-60 psi on all the others. Adding oil to the cylinders did nothing to improve the compression, and while we didn’t do exploratory surgery, it was evident that the replacement engine had spun out of time for some reason – it was dead on arrival and Willie would need to change it out again.

Back on the Phone


I called LKQ and spoke to the sales guy about it; he asked for the vehicle mileage and installation date and had his warranty engineer call me on my cell phone. The call came in while I was at the grocery store late Friday afternoon, and his purpose was to establish the veracity of my claim that LKQ had indeed sold us a junk powerplant and to see if I was a buffoon who had jumped to the wrong conclusion. The guy was nice enough when I explained what we had done and how we had determined the engine was bad, and he wheedled a bit to try and get us to dig deeper to see what the problem with the engine actually was, but I dug in my heels.  This was a bad engine and we needed another one. It was as simple as that.  He agreed.

With iron resolve, Willie went right to work yanking the bad unit back out. The following Tuesday the LKQ truck delivered another 4.6L with 6,000 fewer miles on it, and the engine looked a lot cleaner overall. Oh yeah, it had an 8 bolt crankshaft like the first replacement too, so we’d be able to use our $30 flywheel.

Willie re-did the engine swap in a third of the time it took the first time around.

While that second engine swap was under way I wrote a ticket on a welding student’s 2003 Cadillac CTS that was blowing the right hand low beam headlight fuse – the headlamp assembly was awash with internal condensation and the owner had replaced an inoperative HID bulb on that side, which is no small feat since the bumper cover has to be removed for access. What we found was that that the HID bulb’s very expensive driver module had collected water. That module is mounted in the bottom of the lamp housing and tends to gather water that way. He put that repair off for a bit to explore other options.

While Willie was putting the finishing touches on the F150, a 100,000 mile 2007 Hyundai Tucson came wheeling in with a harsh shift – unless she feathered off the throttle at the point of the shift, the transmission would make a hair-raising slam shift from second to fourth, feeling like the Tucson had been rear ended by a Lincoln.

With my trusty MaxiDas online via the DLC, I analyzed the live data while she drove, and reasoned that the transaxle actually did shift right when she feathered the throttle, and pegged the problem as a software concern. I had her stop the vehicle and kill the engine, then switch the key on so I could reset the transmission adaptive tables. It was pretty amazing to both of us, but that fixed that problem. She was ecstatic, crowing about how she could spend the $1600 she had been saving for a transmission on something else.

And for a photoflash ending that made that a perfect day, Willie fired up the Ford and the second replacement engine was purring like a kitten when it left.  Mission accomplished!  R.W.M.

Leave a Reply

Your email address will not be published. Required fields are marked *