84 Bronco 2 Knock under load

[wildbill23c]

My 84 Bronco 2 just developed a slight knocking noise while under load. If just sitting in neutral or any gear with no load on the engine I can run the engine from idle to floored and the noise doesn't exist, just when accelerating under load up to cruising, once I level off the throttle back to just a cruising speed the knock goes away. What should I look at? Kind of stumped at this one.

I was starting to think that I just have something lose like a bolt or possibly a U-Joint or something of that nature since its only doing it when under load.

 

[kimcrwbr1]

Are you still using the computer? Confirm base timing is at 10 dbtdc and check clean the knock sensor connectors, it is in the block in front of the starter screwed into the block.

 

[70roadrunner]

i was thinking the same thing, ignition timing.

 

[wildbill23c]

I haven't touched any of the timing stuff, it just started doing this yesterday afternoon. So I wouldn't think the timing would just change by itself. I will look into it when I get a chance.

 

[kimcrwbr1]

Clean the connector good to the knock sensor and the way to test it is with a timing light and another person, have the person tap on the block next to the knock sensor while your looking at the timing marks the timing should retard with the tapping. Do not tap on the sensor they are real brittle.

 

[kimcrwbr1]

The timing rarely if ever will change on a 2.8 there is no timing chain just gears.

 

[wildbill23c]

Clean the connector good to the knock sensor and the way to test it is with a timing light and another person, have the person tap on the block next to the knock sensor while your looking at the timing marks the timing should retard with the tapping. Do not tap on the sensor they are real brittle.

Hmm, so if the knock sensor turns out to be bad that would cause the knocking noise I keep hearing? Seems kind of weird that it just started all at once. Seems to be more logical than what I was thinking though of a U-Joint or something. I'll see about looking at it after work this afternoon. Not in too big of a hurry as I'm not really driving it due to a fuel leak, just drove it the other day to have a guy check on some wheels for it that he thought would fit.

One other problem, where do I find a knock sensor if its bad? Can't located a part online at all for it through the auto parts stores.

The timing rarely if ever will change on a 2.8 there is no timing chain just gears.

Kind of what I thought, that the timing once its set doesn't change by itself unless you change something and don't put it back right LOL.

I've heard that those timing gears aren't metal though, that they're some sort of composite material, is that true?

 

[kimcrwbr1]

If you get lucky you can find a good used one for cheap but get ready to auction off your first born if you can find one new. They are also torque sensitive when installing too looswe or too tight will give you a false signal. GL

 

[wildbill23c]

So is this sensor something extremely important? Can I get away without even having one as the computer in my B2 doesn't even work I don't think given the relay is sitting on my desk and has been for the past few months. It just started having this knocking issue on this past tank of gas I put in which was premium don't know if that would cause a knock but that's the only thing different I've done, other than its been sitting for a week because of the fuel leak which I seemed to have stopped temporarily.

 

[kimcrwbr1]

I`m sorry I thought the computer was working the knock sensor is out of play. Your running on base timing at 10 degrees full time it is a wonder you get any power at all.

 

[wildbill23c]

I`m sorry I thought the computer was working the knock sensor is out of play. Your running on base timing at 10 degrees full time it is a wonder you get any power at all.

No problem, I'm not really sure if the computer did work in it correctly before I pulled the relay out due to it going into some sort of limp mode which would give me about 40MPH top speed and was constantly cutting out, like I said after I took out that relay by the computer it now runs awesome except for the stupid knocking noise that decided to show up, which has me puzzled because when I heard it intermittently before it was because the carburetor wasn't adjusted right, I'm not sure if it keeps adjusting itself by vibration or what but I can't keep it at a steady idle to save my life, I get it set once it warms up then it won't stay running when cold, then after a while it is idling high again. The reason I'm confused now is the problem is constant anytime I accelerate from a stop up to cruising speed, before it never had the knock noise this bad.

The Haynes manual says:

Pinging or Knocking Engine Sounds During Acceleration or Uphill:

1. Incorrect grade of fuel.

2. Fault in fuel or electrical systems

3. Ignition Timing Incorrect (ruled that out this afternoon)

4. Carburetor out of adjustment (Kind of leaning back on this now as it seems to keep adjusting itself).

5. Improper spark plugs

6. Spark plug wires damaged

7. Worn or damaged distributor components

8. Faulty emissions system (umm yeah none of that stuff is even present thanks to previous owner).

9. Vacuum leak (tons of those but didn't cause this knock issue before). The only vacuum leak it has now is the brake booster connection that goes into the booster itself is leaking but its been doing that since I got it, and hasn't had the knocking noise the whole time just intermittently up until this past Sunday then its become a constant knock under load.

I can raise the throttle level up just sitting in the driveway and I get no knocking so that tells me at least I don't have a rod about to exit the engine LOL. Although the noise isn't that loud. I've had like this knocking noise before, but after I had the truck in and had some work done and the carburetor cleaned and adjusted it stopped, now the noise is back again, so I'm wondering if the carburetor could just need adjusted once again.

If its the carburetor adjustment, the initial settings for the front screws are 3-1/2 turns out from slightly seated correct? Haynes manual doesn't say a thing about adjusting the carburetor just how to install and remove it, this manual is worthless IMO.

 

[EVOrider]

You may want to check the EGR valve as well....if your truck still has one. When they fail, you can get pinging under load. They're easy to check....

As for the knock sensor....they rarely go bad. Also to mention, there were three different versions called for the 2.8L. If I remember correctly, the 1983-1984 had the same, some early 1985 models had the first one and later ones got a different one. The 2.8L Aerostar either had the 1985 version or the last version only found on the 1986 Aerostar. I believe the only difference was the threads. The knock sensor on the engines actually screw into an adapter. Reason I know this....I had to replace it about two years ago. If you must replace...get the part number off of yours.

 

[wildbill23c]

You may want to check the EGR valve as well....if your truck still has one. When they fail, you can get pinging under load. They're easy to check....

As for the knock sensor....they rarely go bad. Also to mention, there were three different versions called for the 2.8L. If I remember correctly, the 1983-1984 had the same, some early 1985 models had the first one and later ones got a different one. The 2.8L Aerostar either had the 1985 version or the last version only found on the 1986 Aerostar. I believe the only difference was the threads. The knock sensor on the engines actually screw into an adapter. Reason I know this....I had to replace it about two years ago. If you must replace...get the part number off of yours.

The EGR valve is connected to the engine because I don't know what I would cover the hole with if I removed it, however its completely disconnected due to the fact that if I connect it, the bronco will die and won't run at all.

I don't think its the knock sensor, I'm thinking its carburetor related because if I play with the adjustments on the carburetor I can get it to go away or come back however to get it to go away it sits at too high of an idle speed, guess I'll have to live with a slightly high idle for a while till I can figure out what's causing that problem and the knock problem.

 

[wildbill23c]

Ok, here's a great update: The carburetor I had was fouled up somewhere I am now 100% positive on that as I got a replacement carburetor today in the mail from (Thank you again 509lifted). Got it installed, adjusted, and running in 20 minutes and down the road I went, no more knocking noise, and best of all no more fuel leaking on top of the intake manifold.

 

[wildbill23c]

Well the knocking noise has slightly returned, but not near as bad as before. Kind of leaning towards maybe its more of an exhaust noise I'm hearing as I have horrible exhaust leaks right now.