Ok, here we go.

I really need the experts help on this one. Let me start with a little backround. I have a 1987 F-150 with the 300 I-6 MFI (great engine!) 188,000 miles, burns no oil, leaks a quart every 3k from rear main seal, no leaks otherwise, runs decent with a few exceptions (I will explain later), It has a NP435 4-speed trans, but need new release and pilot bearing. In the last 3 months, I have done (or had done) the following: New time gear set (with metal gearset not Nylon!), new spark plugs, wires, distributer, coil tested OK, new exhaust from the cat back. I know that the pre-converter is shot to hell and makes a hell of a racket under load, new belt and tensioner. Other things you may want to know: smog pump still working and not squeling, I have not done the EGR modification yet, (but considering it). I use only motorcraft filters and 10w30 valvoline and STP oil treatment.

This is not a vehicle that sits, daily driver. 30 miles a day or more.

Hope fully that will give enough info to keep the guessing more educated. (LOL) Oh! I remembered something else, NO CHECK ENGINE LIGHT, (works, No codes I mean).

Now that I have thourghly bored everyone reading this, I will give you the problem.

I will give you every symtom i experience. There may be more than one thing wrong. As the title said, I have a intermintent rattle, It is engine speed dependent when it happens, sometimes load dependent. It is not speed sensitive. Most of the time I get the rattle on the highway after climbing a long grade, or hard on the gas for an extended time. Here's the kicker, after I level my lead foot out it it gets louder, I let off completly it goes away, WOT goes away..

NOW FOR THE WEIRD PART.

After crusing at one speed for 5 -8 minutes, the rattle (clatter maybe better description) goes away instantly and completely, but I noticed when it did that, that i had to give it a little more gas to keep cruising the same speed. I could feel the change happen when it went quiet.

I, for the life of me, can't explain it. Maybe this forum can.


Truck never seems to lose much power or MPG's just very NOISY sometimes.

 

bearings. main probably, possibly rods, but deffinately sounds like bearings.

 

My truck does this too...only 12k on the new mill..no oil use or anything.. Although mine is affected by vac advance. Without it i don't get the clatter. With it, i do get some clatter, but its only at high rpms, or if i just shut the truck off after a long haul on the highway.

Its got me puzzled too... any thoughts?

 

Sounds like your EGR valve is sticking. Try some diagnostics on it to see if you can confirm the sound is the EGR. They have a bad horn type of sound.

 

I have a similar problem as well, although I'm thinking its part of my tranny. I have the exact same year, tranny/engine combo, except I don't know if your's is 4x4 or not.

At around 65MPH a rattle sound is beginning to sound at 67 MPH in 4th, there is quite an audible rattle. I was thinking it could be a gasket on the manifold or at the downpipe, but then again I'm having some oil pressure problems as well. The truck runs really strong and makes no noise through any of the gears except for 4th, with or without load at that speed. I'm wondering if the oil pressure problem could be cause by a clogged oil pump screen or the oil pump itself is failing?

My main question is how intesive is it to replace the crank bearings and crankshaft? if that is what the problem is, and how much would I be saving if I performed the job myself compared to taking it to a shop to have the job done ( I hate anyone but myself working on my old truck...).

Any help is appreciated!

 

cryptonik420,

I don't have 4wd , but our problems sound simmilar.

I posted this same post in the 87-96 truck forum also, you may want to take a look at it.

I'm starting to believe that it's related to ignition timing. I can turn my distributer a little clockwise and the rattle goes away, but the truck becomes a DOG ( can't get out of it's own way). I'm begining to suspect two things, either the TFI module, ( have you replaced yours lately?) or the PIP sensor (Hall effects sensor) in the distributor. These two items work together to send a signal to the ECM to control ignition timing, if the sensor is bad, or the TFI is not sending the signal, The ECM uses base timing to run the engine at all speeds.

 

If the PIP sensor is weak, the timing advance will be off and I suppose that could cause the rattle at crusing RPM. As the sensor regains what ever it lost, advance (or any timing adjustment) may start working again. hense Rattle gone or reduced.

This is only theory, but makes some sense ( I think?)

Any one have another opinion? or knowledge of the TFI ignition system?

 

How much are those parts to replace? I'm really not financially stable right now, but I also don't want to walk to work every morning! I'm sure I can get my hands in there and replace those parts.

 

From the Class action lawsuit that was settled by ford,

'In the Related Actions, the plaintiffs allege that Ford knew, but concealed from the public and from government officials, information that its TFI-IV module—which is an ignition-system component that Ford installed on the distributors of class vehicles—had an inordinately high propensity for failure due to overheating. The plaintiffs allege that TFI module failure is more likely to occur in conditions that cause the TFI module to become overheated, such as in hot weather and while the vehicle’s engine is under load (such as while towing or while driving up a grade) or while idling for extended periods. The plaintiffs also allege that TFI module failure frequently occurs on an intermittent basis; that is, the module will fail while hot, and then recover and continue functioning after it cools. In addition, the plaintiffs allege that if a TFI-IV module fails, the engine of the vehicle can stall suddenly and unexpectedly, even while traveling on the roadway, thereby creating an unreasonable risk to motor vehicle safety.'

 

I replaced the TFI module this weekend, but the rattle remained after it warmed up. So I went back and reset the base timing to 10 degrees BTDC, I find out tomorrow if the rattle is gone or reduced when I drive it 30 miles to work. \

In the meanime, any body else have a clue what sensor could cause the timing not retard (de-advance) after hard acceleration? Thats what it seems to be doing.

Another thing, My idle surges when cold, sometimes dies. eventually ( after a couple restarts) stays started. For the short term, I created a vacuum leak with the FPR hose at the manifold.
That bumped my idle up 200 RPM and runs like a champ. I could leave the FPR connected, but the next availble vacuum line increases the Idle to 1200 rpm. TOO HIGH. my Idle with the vacuum leak is 850-900. Idle w/o leak 600-650 and surging.

I do not have any codes that I could retrieve ( am I doing it wrong?). I jumpered the single wire connecter to the DLC ( right side top , not the fuel pump test port either. I know which one that is.) The engine light did not blink, Do I need to use a voltmeter and count needle sweeps? this is a 87, you know first year for EFI on the 300 six.

Any help is appriciated. thanks

 

I have this rattle on my truck as well. It started at the same time I installed my headers and exhaust. At first I thought it was an exhaust pipe hitting somewhere. It's not. I also considered the possibility of a loose baffle in the Flowmaster, but it doesn't do it at idle or WOT unless I lug the engine, just part throttle. It never goes away. I don't have EGR anymore, but the valve is still mounted to the truck. Also no cats, so they aren't rattling. If it was a bearing on my truck it would have blown up by now; it's been almost 4 years and probably 60k miles of me driving like I stole it. I drive at WOT most of the time so I don't have to hear this annoying rattle. If anybody can solve this mystery it would be great.

As far as extracting codes from the PCM, good luck. This computer is about the stupidist thing ever installed in a vehicle. Usually if the SES light is not on it won't know anything. If it does you often have to run the self test procedure to get anything out of it, and there isn't a datastream to look at. Ford might as well have not installed a diagnostic port on their vehicles from this era.

 

sure the rattle from installing headers isn't just an exhaust leak?

 

Yes

 

My truck has similar symptoms. I think the intermittent rattle has to do with the ignition timing also. I've noticed that when the temp gauge is up a little that the rattle (almost sounds like an air compressor at times) is much worse and will start at a lower speed that when the engine is running cooler.

I was also recently on a long road trip and the volt gauge went up several letters on the gauge and the truck ran like new.
So that said I think it has something to do with temperature and a electric sensor. I have also already replaced the plugs, wires, distributor cap, coil, tfi module and set the timing.

My dad is a mechanic back east and he just told me that there is a sensor that reads the engine temp and adjust the timing, but i haven't fooled around with that yet.

dre