Specs: 1991 Ford Bronco, EB edition with 302.

Recently bought a Bronco and it needed the intake manifold and valve cover gaskets replaced. The PO showed me where it was leaking from and the vehicle was taken to a local mechanic(one of his friends, but it was an actual business) to get fixed(at the POs expense). Three weeks later I get told its done(two week delay due to bolts being broken and wrong gaskets being ordered) and i go pick it up.

There was white smoke initially when i started driving it but it slowly went away. On the two hour ride home it would occasionally throw more white smoke, but it was intermittent and usually only when i mashed the gas pedal. The mechanic said it would do that for awhile until the oil that was leaked was burned away but gave no specific time frame on it.

Additionally, and potentially a bigger problem, after driving for about 20 minutes, the engine(or something from the front of the vehicle) developed a knocking sounds(which could be felt). The knocking only occurred in second-fifth gear(essentially past 25mph) and only between 1300-1800 RPMs(give or take a few). the noise did not speed up with RPM increase that i could tell, but did seem to get louder on occasion. Its only occasionally that it does it on 2nd gear(and it isnt a constant even when in that RPM range) but in 3-5 its constant when in that RPM range and not accelerating fast.

There is no knock when in park(regardless of RPM) just when in drive and above 25mph. There is no noise when shifting from park to drive or reverse. There doesnt seem to be any hesitation or loss of power. It did throw a code, but everywhere is close ATM, gonna take it to a shop tomorrow and have the code pulled, and potentially take it somewhere to have a Diag done. Just wanted to hear what some possible problems could be. If i left out any relevant info let me know and I'll try and post it.

EDIT: add info about second gear

 

when you are driving at that RPM in those gears and put truck into nuetral what happens? does the knocking go away? do you notice the white smoke when it knocks?

 

I would do what Kemicalburns says and test to see if the noise disappears when throwing the truck into neutral. Also definitely check for that smoke when it is knocking as well.

I'd try and take a close look at the smoke as well (easier during startup and idling if you can get out of the vehicle and look at it).

WHITE smoke is going to be from water and/or coolant. In the mornings, especially moist cool environments, moisture builds up in the exhaust and you'll always see white smoke at startup untill all the moisture is out. However, if it is dry and warmer out, you shouldn't be seeing white smoke.

BLUE smoke is going to come from oil burning. Now blue smoke won't look like the color of a smurf or anything, it's only blue tinted. It can very easily be mistaken for white smoke.

One way to try and tell a little better what the smoke is coming from is to smell it (if you can, don't shove your nose in the exhaust for obvious reasons) If it smells somewhat "sweet" it's usually coming from coolant. That is if the cooling system has antifreeze in it. If it only has water, then you won't be able to smell it.


As for checking codes, if you don't end up having the chance to stop by a shop to check codes, it's actually incredibly simple to do at home with nothing other than a paper clip. I know there are some good writeups on this forum how to do it, but I found this writeup from steve83 on supermotors which has a bunch of good info on the whole code pulling and reading: http://www.supermotors.net/registry/media/245234

 

White smoke usually points at coolant/water, the knocking might be coming from excess moisture in the engine combustion chamber (water is non-compressible, so the explosion would be stronger, and potentially harmful).

 

Before you take it to another shop search on here on how to check codes and do it yourself.It's really easy.

It sounds like possibly the intake is leaking into the cylinders or a head gasket might be going

Check the oil see if it looks milky under the cap.

The ''knock'' your feeling sound like a misfire to me.

 

Thanks for the response guys! Sorry went on vacation and didn't have any electronics. Anyways. The shop told me i needed to replace or rebuild the engine.

I ran a compression test and had the following numbers

130/0
145/150
148/160
140/160

They looked about the same with a little oil in the cylinders with very little variance from the dry test. Talked to a mechanic(that is a friend and 2000 miles away) and in his opinion, the head needs a valve job. So I will be taking apart that side of the engine to remove that one head and taking it in to have that one valve fixed. Should cost less than $100 and a bunch of my time!

Edit: I'll be draining the oil and coolant tomorrow so I'll check to see if the oil is watery