Ok Folks:
Lets see who reeaally knows their stuff...
I have a 1991 150 with a 4.9L, EFI, TFI-IV, with a 5 speed manual, and a definate love hate relationship with my I6. I purchased the truck with 130,000 miles on it and valve train rattle, which is why I assumed the previous owner thought it was about to fly apart and got rid of it.... (But this was an easy fix... right...)
Over the next 40,000 miles I first replaced the lifters, push rods, springs, and rocker arms. Still had the clatter. Next came all (and I mean all) new sensors and pick-ups. Still clatters. Then a new computer. Still clatters. Then a new distributer, Hall sensor, and TFI-IV module... Still clattered. Took it to the Ford dealer and had a diagnostic done... found NOTHING wrong, and advised me that I had "valve train clatter" symptomatic of ANY high mileage I6. I really can't stand ANY noise, so I saved my pennies and had a new long block and ALL new accessories put on. There was nothing old left on the truck.
Life is good. No noise. Silky smoothe...for 5,000 miles. Now the VALVE NOISE IS BACK!!! I'll try to describe all symptoms as best as I can and hope someone can help.

No tapping at idle or when the engine is unloaded. No tapping under wide open throttle. Clatters to different degrees at all ranges in between. (sounds just like the timing is too high or poor quality gas, even though I use 93 octane and timing is to spec). Check engine light comes on randomly for about 5 seconds at a time under cty conditions. ( pulled the codes and never get anything other than all ok), and does not come on highway driving. Randomly in first gear from a stop, the engine revs just fine, but there is no power, then suddenly in pops the torque. ( acts like the timing jumps from full retard to full advance.) Once or twice a week under WOT, the engine has a split second ignition or fuel cut out. (lasts about as long as it takes to snap your fingers).
With the SAME thing occuring to two different engines in the same truck, I'm beginning to think it is demon posessed.

Any takers on this one?

Any and All help appreciated.
Phillip

 

Have you checked the fuel pressure. this sounds like a fuel delivery problem. If the pressure or volume is to low this can cause a lean condition and pre-denonation (valve rattle) it also would explain the loss of power or erratic power. Just a though.

 

[updated:LAST EDITED ON 28-Feb-02 AT 04:04 PM (EST)]wtroger may have a point, but in the searches I've done on the engine in the FTE boards, even new truck owners report it after low miles, and live with it throughout the long lives of our sweet I-6's.

There again, mine has no noise. 85,500 miles and it runs better than when I got it.
Updates that could have made all noise go away:
Mobil 1 syn. oil 10W-30
Purolator Pure 1 oil filter
EGR restrictor plate (which might make it run less lean if wtroger is right about that condition).

(and for probably non-related engine updates:
Autolite plugs
MSD-6A
New cap and rotor)

It used to have a rattle upon start-up - and the previous drivers seemed to indicate it was always with it (I'll ask them this weekend for ya), but the thing idles like a japanese car now. Go figure.

Believe it or not, that 'cut-off' of power at the beginning is probably the same problem a lot of 4.9 posters on FTE, including me, went to the EGR restrictor plate for. Done right it should get rid of the problem - without that part, driving around town (stop signs and lights) was a real pain.
Best of luck to ya.

 

Thanks for the info.

I had previously ruled out the fuel delivery area since I had changed the filter and put new ingectors in with the new engine and have dual tanks with seperate pumps; however I have not changed the fuel pressure regulator. I'll throw a pressure guage on it this week end and a new regulator.

I've seen several referances to the EGR restrictor plate in other forums but cant find any specs for one. Is this a Ford item or back yard grown?

Phillip

 

It is a home grown deal. Use a gasket as a pattern and cut out a blank from some sheet metal then on the hole that goes into the intake just drill an 1/8 or 3/16 hole sandwhich it in between the egr and the the intake. There are some threads on this around. This fix has helped a lot on i-6 motors drivability problems.

 

Use two brand new gaskets on either side of the restrictor plate, plus a high-temp, non-o2-interfearing gasket sealant on all sides of the gaskets and plate.

I used two 1/8" holes centered in the two EG recirculation holes for the gaskets (plus two equal-sized holes for the two bolts), but it has come to light that one of the two holes is blocked off anyway fro the factory on some trucks... nonetheless, do both anyway and you'll have it covered. It is a vacuum dependant connection, so failing to clean the sealing surfaces or make a new air-tight seal with the plate will cause you troubles.

I made sure all cuts and drilled holes were stone and wire wheel smoothed to make the surfaces flat for installlation.

The funny part is that it is so cheap of a part compared to all many have changed, or many considered changing, and that it fixes a lot of the inherant problems.

 

Hey, I did the EGR plate 2 weeks ago, it does seem to be a good thing. My motor runs great. However, in another posting I mentioned how noisey my motor USED to be (only at start up), my 18 wheeler neighbors thought my truck was a diesel too! I envisoned I had a cylinder that was too loose and the piston was clattering around. I started using Slick 50 stuff and its quieted it down perfectly and stopped the valves from tapping. I tried Valvoline Synthetic but it created an oil leak.

I think yours is something else. Like ignition, spark advancing too much or not enough or maybe the coil is weakening. Moderate wear on the mechanical parts, pistons... will trigger a code (within reason).

 

Make that NOT trigger a code for the pistons, valves...