Dieseling/Chattering Sound?

[mknight]

Okay....I need the help of all you more experienced mechanics out there. I have a '94 F250 4x4 ext. cab with the 5.8 liter V8 in it. I've had the truck for about 3 1/2 years. During the past couple of months I have begun to hear a sound from the engine while driving that almost sounds like a dieseling sound or rattling/chattering sound (don't you hate it when people try to describe the sounds of their mechanical problems :-)). It also sounds kind of similar to the sound a car with a manual transmission would make when you try and let out the clutch in too high of a gear. It is most present at lower rpms at all different speeds (i.e. I can be going 30 mph but at a real low rpm (on the gas) and it will do it, or even more common is at higher speeds, and especially when under a load).

I am not a four-stroke guy, but I hear of "adjusting the valves" all the time and I know there has got to be comparable maintenance on a truck like this. Any ideas on what this sound could be?

This past weekend I took my family for a camping/riding trip in the west desert of Utah. I was pulling my 23 foot camp trailer and the bed of the truck was pretty loaded down (bikes and gear), and I could really notice it then. I was doing about 65 mph with cruise control on (overdrive off), and it would typically happen when approaching a slight grade.

The truck does not blow smoke at all and it gets consistent gas mileage (13-14 not towing, 8-10 towing depending on load). Is this an indicator of something serious or could it be just a gas issue or other small maintenance issue? I usually just run regular grade gas (85 Octane here in Utah), but have not tried a higher octane to see if gets rid of the problem.

Thanks for any responses.

 

[leeinmemphis]

http://www.ford-trucks.com

I believe these people can help. They have some very knowledgeable people on the board. Good luck.

-lee-

 

[MRRMX]

85 Otctane rating, I never seen under 86 rating.I would see what the owners manual says on the octane rating. all our work trucks Ford or GM call for 87..............

 

[R White]

mknight the reason the oct. in ut. is so low is the altitude plus flying "J" is making lots of $$$$ with it. I know a good mec. in your area. sounds like timming has moved but not much. on Wall ave. in ogden around 32 so. david early tires.talk to ralph the manager he'll piont in the right direction. dont know if hes still there, moved from there in 96. folks still there in wash. terr. all my kids learned to ride on the mud flats @ Dell. miss all the places to ride there but don't miss the low wage :p good luck W/truck

 

[agitt73]

one word TRANY
is getting weak
my truck has 97,000 and is staring to do the same thing
but mileage makes no differant ive seen the over drive tranys
go out any where 60,000 to 150,000 miles on them;)

 

[mknight]

Thanks for the replies.....the truck has 107K miles on it and the tranny was completely rebuilt at about 82K. That certainly does not mean it is not going out again, but the sound I am hearing seems to be distinctly coming from the engine compartment, and it is not consistent with the symptoms I remember experiencing when the tranny went out before. I'll continue to watch it and I'm definitely going to try a few tanks of higher octane.

RWhite...thanks for the referral. I know of the "mudflats by Delle" you described. I've ridden there many times with my son and one of our favorite places is just another 30 miles west of there at Knolls. Lots of great riding!

 

[agitt73]

rocker arms or oil pump

 

[dirt bike dave]

To me your description sounds like the engine is pinging under heavy loads. Increasing the octane may be all you need to do. Pre-ignition/detonation is VERY hard on the engine. If the increased octaine doesn't solve the problem, check the ignition timing and also make sure the cooling system is working correctly.

 

[mtngoat]

Agree with DBD above. It sounds like detonation, which can be very hard on the motor, if excessive. Since it sounds like it's developed recently, I'd focus on your fuel injection (if so) system and consider a injector clean-out by the shop or initially a fuel additive.

 

[MRRMX]

A slow O2 sensor will cause this symptom. I had a converter become blocked on a pick up at work, It caused all kids of motor noise. You would be complaining that you loose power as you drive.

 

[gnarlykaw]

might be of help

do you have a "check engine "light on?
most likely, the e.g.r. system may be getting clogged, also, go to a higher grade of fuel too.......

 

[Jonny426]

I'll agree with DBD, Mtngoat+Gnarlykaw. ping/detonation sounds right and it is very hard on pistons/bearings.Check ,or have it checked, the timing(cheap fix).Verify E.G.R. operation.( If the E.G.R. is messed up it should throw a check eng. lite on in '94.) Even if the valve moves, it may be blocked or restricted by carbon buildup. If you fill up with super unleaded and notice a definate improvement you are supressing detonation,And timing/E.G.R. are major factors.A weak fuel pump or partly blocked fuel filter will cause a lean condition wich can cause ping,but that too should set a code/cause the check eng. lite to come on. 23 long years ofauto repair,most of them ASE cert. Jonny426

 

[MRRMX]

Originally posted by Jonny426
I'll agree with DBD, Mtngoat+Gnarlykaw. ping/detonation sounds right and it is very hard on pistons/bearings.Check ,or have it checked, the timing(cheap fix).Verify E.G.R. operation.( If the E.G.R. is messed up it should throw a check eng. lite on in '94.) Even if the valve moves, it may be blocked or restricted by carbon buildup. If you fill up with super unleaded and notice a definate improvement you are supressing detonation,And timing/E.G.R. are major factors.A weak fuel pump or partly blocked fuel filter will cause a lean condition wich can cause ping,but that too should set a code/cause the check eng. lite to come on. 23 long years ofauto repair,most of them ASE cert. Jonny426

Does the ASE for auto ask hard, Tech. question? I Have the heavy ASE cert. I'm not totally sold on ASE. I know a tech. that is ASE cert. in heavy trannys and never had one apart. He is great with the gas engines and has all the ASE cert. I was gassed when one day we were riding back from the plant in a tractor and he was driving. He was raking the gears on the high side. I said man, Leave some for the driver. He spoke up with the syncros are whipped......Thats when it hit me He's ASE cert. in heavy trannys...for those who dont know tractors with 9 speeds are non synroed trannys. The Aux section is syncroed but the main box is not.:eek:

 

[gnarlykaw]

some are.....

the questions go back and forth, meaning, some are hard, and some are just plain outright dumb questions. I am master cert., L1 auto tech. i have been at it for 25 years.:D
Did ya get the E.G.R valve and circuit looked at yet??:silly:

 

[Jonny426]

MRRMX, ASE is kinda funny. As you said you know a guy who's cert. in heavy truck trans. that can't even tell what he's working on. I know some really good mechanics who just can't score well on paper but can fix almost anything.If you're thinking of taking some tests,get the sample tests and study guide from ASE. They will give you a good idea of what to expect when you go to actually take one.They have a site,ASE.org. I think, but I'm sure you search it out. Jonny426