Hey,
I just bought a 1990 f150 with 59,000 original miles from an 88 year old guy who took great care of the truck. Today I just noticed a slight rattle (like a paper clip in a galss) only when accelerating. Anyone have any ideas? I am worried it could be serious....

 

It could be a timing ping due to poor grade gass.
A loose spark plug, is it a 5.4 engine.

when there is more exhaust gass from hard accelerating can cause exhaust rattles.


hope it is an easy problem to solve.

 

Welcome to F150online.

Its sounds like you have detonation.
This can be caused by quite a few things.

1. Bad Gas. Make sure you are using a reputable brand of the correct octane rating.

2. Carbon build up in the combustion chambers. This can lead to hotspots in the cylinders. The previous owner may not have given the truck its head much of the time due to its age or only done short journeys. You could try a couple of cans of the Seafoam treatment. Do a search for this.

3. Incorrect ignition timing. Have it checked.

4. Wrong heat range spark spugs. Again, a full service probably wouldn't hurt.

5. Blocked fuel filter. See above.

6. Fuel mixture too weak. See above.

7. Vacuum leak causing a weak mixture. Are all the hoses on a nd not perished?

8. Lugging the truck under load in too high a gear will cause detonation.

Hope some of this helps and gives you a few ideas.

 

It is a 5.8 L V8. Loose spark plug? Perhaps. How would that cause a slight rattle when accelerating? So if it was low grade gas.....would it be a valve that's rattleing? Does that mean anything as far as the life of the engine?

 

wow....great advice. I am new to this site and can't thank you guys enough for the advice. I had a car before this truck and am instantly getting excited about learning as much about engines as I can. Hopefully I can keep her going strong! A tune up is definitely in order! He let it sit a lot and I am sure condensation led to the rusty spark plugs. But the truck drives like a dream and looks like it did in 1991!

 

That would be the exhaust gass's from the cylinder's firingleaking past but also the combustion noise. That was a problem with some of the 5.4 engines as they had 2-3 threads on the sparkplug to head connection.


Low grade gass causes pre-denotation as can carbon build ups as English Adam pointed out. No the valves most likely are not loose.

In the long run these trhings are bad for the engine.



I reread your post and noticed the year is 1991. The 5.4 and spark plugs are not a concern :o

 

Unfortunaltly I have no idea on your rattle , Just wanted to welcome you to the site.

 

awesome advice. Thanks guys. I learned a lot. And you are right on the 1990 and the spark plugs. I just meant it barely looks a year old. I will change the plugs and wires myself and get the timing checked. Thanks again!!! I hope this truck will go for years. I have a shot with only 59,000 on her

 

That was almost a high jack so now it is.
Hey Rosie, how you been doing?

 

Hiya silver, I'm doing good, cold here tonight now I'm just waiting for the snow!



How are things with you??

 

I am doing well... NO snow NO snow. Looking at the forecasts for tonight you just might get some. I beleive there will be some to the north of you. On the coast it is just more rain.


Saw that movie tonight the prestige. Very good. a movie with an unguessable twist at the end. Well done.

 

I watched the news earlier and they aren't predicting snow this week, just very cold. Our low on Tuesday is supposed to be 17°

I haven't heard of The Prestige. Who's in it? Last movie I saw was on PPV, Poseidon. I know a lot of people didn't like it but I thought it was good.



Edit: Stupid smilie site isn't working. . .again. . .

 

I apologize my queen, I need to take this guys thread back for a minute....


I'd go for a combo of carbon build up and gas.

Carbon build up combined with to high octane can also cause this. It gives earlier detonation which gives the symtpoms of retarded timing.

I'd suck 1/3 can of seafoam through the brake booster line then dump the rest into a full tank of 88 octane fuel if available in your area.

Another common issue the early 90's Ford V8's had is called cross induction firing. Common on the No7 and No 8. cylinders. due to the plug wires of those two cylinders sitting too closely together Induction crossfire causes the No. 8 spark plug to fire twice, the first time about 45 deg sooner than it should. This leads to severe erosion of the electrodes, with subsequent detonation and related engine damage.

With so few miles it is likely that it has the original spark plug wires too. Which would lend to this condition.

So what I would do....
Seafoam the block first then change the PCV, fuel filter, spark plug wires wit hseperators, dump the rest of the can in the tank and run that tank of fuel out. Then New spark plugs.

Even if that doesn't fix it.... it needs it anyway.

Also treat it like a brand new engine. You'll have to break it in. It likely really hasn't been used yet. Do not hot rod it for the first 500 miles. Run it up and down the highway during that time, then change the oil then slowly start driving it like a normal vehicle.

When properly prepared this truck will probably last 250K miles or more, or another 20 years......

 

when you say seafoam the block...can you explain that more? I know a little bit about engines but am just learning. All that advice sounds great. I am heading out to the parts store today to get started. I think she definitely needs a good tune up! The spark plugs are the only rust on the whole truck.

 

It might have had some bad gas in it if the old timer let it sit too long.Probably wouldn't hurt to change the fuel filter too.