Engine knocking

[DeeBo]

Our RV makes a loud knocking when all 3 of the following occur simultaneously, overdrive kicks in, engine fan system turns on and accelerator is pushed. Does anyone have an idea of what could be causing this? Thanks so much for any help.

[Turtle_n_Peeps]

Do yourself a big favor and take your RV to a competent mechanic. Nobody here is going to be able to help you. It could be dozens of things that cause what you are talking about.

Don't know a competent mechanic? Ask around to find one. Mechanics are easy to find. Real good mechanics are hard to find. Find a real good one and get this fixed. This could be a serious issue so get it looked at ASAP.

[TyroneandGladys]

Our knocking was caused by a leaking intake manifold caused by a failed intake manifold gasket. You would think they would have gaskets that would last longer than 27 years.

[tsetsaf]

If it is a single knock it could be an engine or transmission mount, u-joint, or loose ac clutch too. A competent mechanic can trouble shoot this.

[Ivylog]

darsben wrote:
Rereading I wonder could the vacuum advance be screwing up as in the vacuum line be collapsing

No vacuum... no advance. I agree with trying a tank of preium gas or several cans of octane booster if tank is full. If this stops it then you know you have a timing problem... to advanced. Get the timing fixed and go back to regular gas.
Decades ago I used to time my engines by advancing the timing until the engine knocked on hard acceleration and then back it off a little. Does a 03 8.1 have a knock sensor?

[majorgator]

Go see a different mechanic. End of story. A question/answer session on here isn't going to help you, especially if you're not prepared to fix it yourself. What nodody has asked yet is whether or not you're getting any codes or CEL (SES) lights.

Take it somewhere and have it looked at. You want fix "loud knocking" with premium fuel.

[weasel4]

Years ago we had a vehicle in the shop that exhibited a loud knock on acceleration, turned out to be the torque converter acting up.
BTC

[free_radical]

DeeBo wrote:
Our RV makes a loud knocking when all 3 of the following occur simultaneously, overdrive kicks in, engine fan system turns on and accelerator is pushed. Does anyone have an idea of what could be causing this? Thanks so much for any help.

Here's a good mechanic that should be able to help

https://youtu.be/78gACOPUzuM

[darsben]

Rereading I wonder could the vacuum advance be screwing up as in the vacuum line be collapsing

[tpi]

I agree with a post above, to start try a full tank of premium fuel. See if that changes anything. If so it is spark knock (preignition, engine ping). Then post back and we can go from there.

[DeeBo]

There are about 60K miles on the engine. The most important thing, I think, is to note that you have to have your foot on the accelerator for the knocking to happen. Also, the knocking is quite loud...certainly not a "tapping" if that means anything too. I can't tell you how much I appreciate your help. I'm female and know nothing, and my mechanic doesn't seem too "in the know" about RV's...so I'm concerned.

[TXiceman]

How many miles on the engine. It may be a carbon build up in the heads and is causing pre-ignition. Premium fuel will help.

Have the engine checked for proper timing and advance.

Ken

[azrving]

Loose, cracked flex plate?

[DeeBo]

2003 Tiffin Allegro Engine is a Workhorse 8.1. Thanks!

[Mike_Taverniti]

Try using premium fuel and see if that helps. Cost more but may be worth it.