Detonation

[gulas47]

My explorer has been knocking pretty bad for a while now. I was pretty sure that these 4.0s didn't need high octane gas, but what is the compression ratio on these engines. I started running 89 octane and it is still there.
Is this a common problem with these engines? Is there a fix? Any suggestions are appreciated.

Thanks

 

[leebo]

I'd give your plugs and wires a check. This hasn't been a problem with most the explorers I've heard from.

Welcome to the site....you will find every answer you'll need all right here.

 

[Paul Gagnon]

Mine used to ping pretty bad. I had to use premium fuel. Once I changed the plugs the pinging went away and I could return to regular fuel. Plugs and wires should make a big difference and it should help with power too.

 

[CHH777]

While you're at it clean your MAS and disconnect your battery to reset the computer.

 

[gulas47]

Thanks guys,
I changed the plugs/wires about a year ago and it's probably time again (I've put on about 30,000 miles since then). I'll also make sure the MAS is clean also.

Thanks

 

[Rhett]

I cleaned my MAS, changed plugs + wires, and reset computer. In my case it still has not entirely stopped the ping for me. I am searching for why it is still pinging.

 

[brandon11]

Originally posted by gulas47
My explorer has been knocking pretty bad for a while now. I was pretty sure that these 4.0s didn't need high octane gas, but what is the compression ratio on these engines. I started running 89 octane and it is still there.
Is this a common problem with these engines? Is there a fix? Any suggestions are appreciated.

Thanks

I can't run lo octane fuel either unless its 93 it ticks especially under a load/aceloration

 

[rockylaurence]

Do a Search

Yes it is common and a lot has been written. I've done it all (except turn it in to Ford)to correct it. I looked up my records and found that Ford replaced the MAS when I had the problem under warranty. Yes I have cleaned the Mas several times, but the Ping still persists. I've also changed the O2 sensors and run tons of cleaner through the fuel system and directly into the T/B. I'm going to check the price on a new MAS this week.

 

[Mike 92 XLT]

The real problem is the lower intake manifold bolts need to be retorqued. You can reach a couple of them without taking off the upper intake. That's going to be one of my summer projects. Mine pings even using 93 octane and I've tried all the above fixes. Resetting the computer helps for a little while but the problem always comes back.

peace

Mike

 

[Kevin Zeller]

The early engines did not have EGR. These engines will have a problem with detonation. Nothing can be done but run high test fuel.

 

[Bill MacLeod]

Pull #5 spark plug. If you find deposits on it, you may
have found your problem.(coolant leaking past the manifold
gasket, creating a lean condition)
Fix is to pull the upper manifold and retorque the lower
manifold to specs.While you have it stripped down, clean
the maf, tb, bypass valve, upper intake runners and reset
the computer.
It solved my spark knock (only 7 bucks for the upper gasket)and dropped my oil consumption to 1/4 of what it
was, as the back of the lower manifold was leaking oil.

If you need any other info, contact me
wcpm@sympatico.ca

 

[gulas47]

Hey, thanks for the feedback guys. As soon as I get the 4.10s in the rear of my Z28 I'm going to try some of these things out.

Later