I have a '97 with a 4.6 engine that isn't original. I bought it with what appeared to be a loose timing chain so it wen to the mechanic's for a new one. I got it back and hit the highway and rattled real loud, slowed and died on my. Inspection showed the valves were bad so those got done. Went back on the highway and it started rattling again, slowed and then died. Back to the shop to learn it burnt out the plugs and damged the intake valves in the # 7 & 8 cylinders. The truck has the following new:
Timing chains, water pump, valves, plugs, coil packs, plug wires, oil screen and a couple of main bearings (the oil pan was pulled to inspect under the engine to play it safe).
Now it is back together and runs but the mechanic said when they speed up the engine past idle the TIMING SLOWS DOWN!
The computer checks out fine with no problems or errors showing.
So, has anyone come across this and does anyone have a solution? Thanks.

 

How many miles on the engine? Also you have to define "rattling" is it detonation, valvetrain/timing chains, overheat etc.? Once you determine what is rattling then we can take a shot at what is causing it. Detonation for example could be a tank of bad gas. Overheating could cause the ECM to go into failsafe/limp mode. Valvetrain could be low oil pressure allowing lash adjusters and chain tensioners to collapse.

 

If it died and valves were bad id say they didn't have the chains lined up correct and it bent valves. Aka their fault. Sounds like idiots are working on it regardless

 

Rattling was a loud rattle sound like a loose timing chain in the front and a very loud knocking sound near the rear of the engine; both prominent under acceleration with or without a pop up trailer attached. Sounds were there before and after timing chain was changed and after all the valves were replaced. The truck slowed down on the hwy and then stopped running; it was determined the timing was off and it damaged the valves and burnt out two of the plugs and in only about 10 miles distance. No indication of overheating, it has a new thermostat. Oil preassure is within specs (preassure tested with guage) and the screen was just replaced. I forgot to mention is also has a new Battery and Fuel filter. I was talking with the shop today and they said the timing actually slows down when they increase the engine speed. Not sure if this helps you out or if you have seen an engine where the timing slows as it is accelerated.

 

So chain tensioner was bad and timing was off causing valves to meet pistons? Then they fixed it and said that the timing that they set was off and it screwed up again? If that's correct then wow. Plus why pull an oil pan off unless it damaged pistons too if so you probably now have bottom end issues thanks to their awesome abilities. Also, timing is controlled by cam phasers and ecm. I don't understand the problem with the truck now. Regardless of the timing how does it drive? Does it knock? What are the symptoms?

 

Get a new mechanic ASAP as these people sound like absolute idiots and have no idea what they are doing. I hope you are not paying for these guys to constantly screw up on your truck

 

No cam phasers on a '97, at least not that anyone on this planet knows about.

Agree that he has Mr. Clueless working on it!

 

Again how many miles on the engine? Not sure its even worth repairing after these guys worked on it. You may be better off getting a good used engine and having someone other than these "mechanics" do the work.

 

Lol **** I forgot its a 97 and a 4.6 it was late at night sorry

 

Don't worry about it I do that kind of stuff on a regular basis here..lol