My old 94 Bronco is finally giving up on me. Yesterday when I first started it, it shakes and could barely keep idling. Then the check engine light comes on. When I drive it, it doesn't have much power and if I press gas hard, I can hear this heavy metal knocking kind of sound from front below.

But if I slowly get it to speed, everything seems normal again. The engine runs OK by itself. I have the transmission (E4OD) rebuilt long time ago.

I have a scanner for this car but it's the old type and very difficult to use (I tried once and never got any code).

Anybody had same problem before? What may cause this? Thanks!

 

Which engine? Mileage? Had any symptoms leading up to this? What does the temp. and oil pressure look like.

 

5.8, around 96K. It gets noisier. Temp and oil pressure look normal. Thanks!

 

I'd suggest pulling Codes in most cases but this one sounds more like a cracked rod or loose bearing cap than anything else. You can drop the oil pan and have a look if needs be. You can also pull Codes the old fashioned way with a paperclip and counting the Check Engine Light flashes. Check here for details on the procedure. Again, you have Codes generated, that is for certain. How much help they will be in diagnosing a heavy metal knock is questionable.

I drove an old Pontiac wagon for six months with a cracked No. 6 rod before it finally gave up completely and punched through the block wall. Sounded just like you described but ran well enough to get around town.

 

Since I failed to pull any codes, I drove it to a shop and let them do it. They spent one hour and can't do it, called me to give them 2 more hours. I will check how they are doing. I will also tell them to drop the oil pan. Thanks!

 

im with grey it sounds like a connecting rod or something similar. which will be some cash. prob either new engine or rebuild. hopefully the techs will find something else that it is but this is the first thing that comes to mind.

 

If it's the connecting rod, doesn't it make higher and higher frequency knocking with speed? I don't hear that. Actually when the truck moves at higher speed, there is no sound at all.

Could torque converter make this kind of sound at lower speed?

The shop is still checking it (yes, it took them more than a day already!) and I will keep you posted once they give me a call.

 

The shop just called me and told me it could be the computer problem and they have to buy a control unit, put it in and try. Because without it, the car doesn't know what to do. I am not fully convinced but have no other options. Just hope they are right...

 

The shop just called me and told me the truck is fixed after they replaced the computer... I am still trying to figure out what happened.

 

Maybe the computer was sending a code incorrectly to cause the motor to knock or something at an idle speed. I don't know computer systems for cars so i don't know what could cause it. Hopefully you don't run into more problems they can get costly.

 

I guess on this truck, if the computer is gone, nothing works. Engine is knocking, transmission doesn't shift, fuel pump is running wild (I remember when I turn the key to on position, I can hear the fuel pump noise)...

Since they fixed it, I'd like to ask every-body's opinion on the way they charged me:

First they told me they need one hour to diagnose the problem ($100). Then they told me they can't find the problem and need two more hours ($200). Then they told me it's the computer problem ($500) and installation costs $100. So total $900.

Since I never done this before, does this sound right?

 

3hrs of dignostic time seems really high to me, you could have saved yourself the install cost and put it in your self but that would have made you liable for defective part. it doesnt sound to terrible, just the diagnostic time seems inflated

 

I don't know about the place you took it but my work doesn't charge 100 per hour of diag. For normal people it is about 90 and for me (employee) its like 60 if it isn't free. As for the installation that sounds a bit high and the computer cost is a bit high but you didn't get screwed. If you had it would have been 1k+.

 

Hold the phone guys, the computer won't make "heavy metal knocking sounds from below" or even cause the engine to do this. So just throw that idea out the window. the computer controls fuel/air ratio, ignition timing and emissions equipment. The 5.8 doesn't even HAVE a knock sensor. Furthermore, the Codes don't do anything but provide diagnostic information. If the computer gets enough incorrect or "unexpected" information from the sensors it will automatically go into "limp mode which PREVENTS the system from damaging the engine.

To be honest, telling you that they needed to replace the computer without first telling you exactly what they DID get from it is pretty far fetched. There are Codes for everything up to and including a hard fault memory failure (think of it as a hard drive crashing) or a loss of reference voltage. The ONLY possible scenario I can think of that would leave the computer inoperable and unable to get ANY information from it would be an electrical failure that would render it completely dead. In THIS case the engine wouldn't even turn over. And it takes about 20-30 minutes to run BOTH a KOEO and a KOER test and that INCLUDES the warm up time on the engine! Neither test requires taking ANYTHING apart. 3 hours of diagnostics? Seriously? And THAT when the engine was still running? Sorry but that is beyond "fishy". If the truck runs great now, get under the hood and have a look at exactly what parts appear new. If nothing has been touched, or appears new, and they did replace the computer without troubleshooting anything else, I'll bet dollars to doughnuts that you will have the same issue or worse within the month.

 

I remember getting a knocking sound a couple of years ago on mine. The top of the shroud had sagged into the fan. I installed a strip of angle between the fan shroud and radiator lifting the shroud enough to no longer be hit by the fan.