Spark Knock

[2003XLTSpencer]

Hello all, Ive got a 2003 4.6 XLT and I'm experience spark knock on acceleration. Any ideas as to why this is happening?

 

[GAINMOB]

what is spark knock?

 

[Gruz7]

Hello all, Ive got a 2003 4.6 XLT and I'm experience spark knock on acceleration. Any ideas as to why this is happening?

Not quite sure what that means but if your talking misfire then maybe it's time to change the plugs and coils...


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[Skauber]

Perhaps he means pre ignition knocking/detonation or pinging?

 

[Skauber]

If yes, it can have several causes, or combinations of causes. Among the most common (in no particular order) are improper ignition timing, combustion chamber deposits, improper EGR system operation, ignition system crossfire, a defective knock sensor or low fuel octane.

 

[2003XLTSpencer]

how does one test for a properly operating EGR?

 

[1955moose]

You'll need a vacuum pump, you can get on at any auto supply store. Remove hose with engine off install hose from pump, pump up to about 20 inches vacuum on guage. If egr valve is good it should hold vacuum. If it drops you have a bad valve. I usually put hose against my finger first then pump just to make sure pump is good. Second start SUV warmup vehicle attach hose from pump to egr pump up again to 15-20 inches motor should stumble and want to die. That test tells you that port from egr to motor is clear. If it doesn't stumble you need to remove egr and clear passage. They get carboned up and blocked. Make sure the first test passes. Good luck, keep us posted. P.S you shouldn't need above 87 octane if all else is good. Moose.


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[2003XLTSpencer]

thank you sir

 

[1955moose]

Your welcome, as always start with simplest first. Have a Midas or whatever shop that can run your dtc computer codes for you. Most do it for free. Have them do so. You don't want to start changing parts all willynilly. Keep us posted, Moose.


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[2003XLTSpencer]

i disconnected the vacuum line going from the egr solenoid to the egr valve and am getting no vacuum at steady 2500 rpm which leads me to believe that the solenoid isn't working properly. There is vacuum going to the solenoid

 

[1955moose]

That's what it sounds like. Put your thumb against hose going to egr rev engine. If you feel nothing, probably solenoid. Are their any other solenoids like it you can swap to be sure? If not might have to spring for one. Be carefully with wrecking yard ones they may be bad too!


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[Lostneye]

If yes, it can have several causes, or combinations of causes. Among the most common (in no particular order) are improper ignition timing, combustion chamber deposits, improper EGR system operation, ignition system crossfire, a defective knock sensor or low fuel octane.

A weak fuel pump can cause this as well. Had that problem on my Lincoln Mark VIII.

 

[1955moose]

Besides the detonation, how's the power particularly on grades? Not a bad idea after you correct egr problem to buy or borrow a fuel pressure guage to fuel injection port. Should be above 35psi. Is that correct guys?


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[2003XLTSpencer]

I feel a little suction but not nearly as much suction as the solenoid input line

 

[1955moose]

As long as it's got enough to pull open the egr valve. If you have a vacuum guage put it on the hose rev engine and see how much vacuum their is. If reading is lower than specs, test at dpfe sensor, and egr solenoid. If you don't have the repair DVD. Theirs a procedure on line that walks you through it. Let us know what you find. Was the egr port clear when you tested it? You did test it didn't you?


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