This is such a basic engine that I'm really hopeful that someone can help me. I have, or had, 275,000 miles on this 300 4.9L. It has had a bottom end knock since I bought it with 198,000. It does not burn oil at all. The valves do not tick at all.

Today on the interstate I noticed the knocking getting worse and then I lost power. No loud bangs at all. It stills turns over and is not leaking any fluids. The temp was fine and the oil is not contaminated.

Issues to note: 1.) when you turn it over it has a lop-sided kind of sound that is otherwise somewhat normal, 2.) it does not knock while turning over.

I am so busy that if I don't come up with ideas to give the shop that towed it for me that I will have to give it away. It is in too good of shape for me to be OK with this.

Should I be able to find the problem just by having them look at the bottom end with the oil pan off? Could an engine that is healthy other than the bottom end be fixed without a major rebuild possibly?

Tanks so much in advance. I'm panicking.

 

It would really help to know the year. If it's an '87 through '91, I would say it's a very good chance the ignition module on the side of the distributor went dead. Also possibly the PIP in the distributor or the coil went dead. Post back with the year.

 

Is it a 4x4? You have to raise the motor to gain enough clearance to pull the oil pan.

I'd check for spark.

Adrianspeeder

 

hey adrian is that you from FORDification?

 

It's a 1993 F150 XLT Regular Cab with 4.9L EFI and a reman Mazda 5 speed with 15000 miles on it. It has all new gaskets, new starter, cleaned intake, always fresh fuel filters, always Mobil 1 oil. It's well-maintained. New shocks, new cooper tires. A real shame to lose the engine when I have no time or space to look at it myself.

I thought I would share some typical noise behaviors of the engine. Under idle, worst knock possible. Under constant gas, not coasting or accelerating, moderate knock. Under acceleration, very little knock. Winding down, or revving down, no knock at all. I think it's a connecting rod at the crank, but I really don't know and can't check it myself. I really need to just tell them to go through certain steps to make sure it can't be easily fixed. The mechanics, who I don't know at all, claim the engine has to be shot, which I know isn't true. It turns over fine, although it sound like it's turning over a lopsided engine, for lack of better words. And when it broke down there was no knocking at all and doesn't knock turning over. No fluid leaks either. I'll have them check compression, fuel pressure, spark, and look up through the oil pan.

 

Sounds like it could be a shrunken piston to me. I drove one about 4,000 miles before I figured that one out. It seems if a aluminum piston is hot and it gets water on it from a bad head gasket it will shrink. If I pulled the spark plug wire off the knock would stop.

 

Problem determined. Broken timing chain. Still burns no oil at all so I am very happy. THey're chargine me $200 in labor to fix it. Any more, I'm just happy to pay the ridiculous hourly rate if they're just honest. I'm happy with what I'm getting considering my truck is broken down out of town and they could ream me badly.

 

The 4.9 liter 6 cylinder engine doesn't have a timing chain, just 2 timing gears that mesh together. One of the gears(the larger one that goes on the camshaft) is probably a nylon composite and has sheared some teeth off. I hope those pieces of nylon don't later get sucked into your oil pump and lock the oil pump up. I would try to get them to flush the oil pan out as best as they can with the drain plug out. I had these nylon pieces lock up the oil pump on a Ford 390 once.