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Preignition knock

Tiny
HOPK6344
  • MEMBER
  • 2002 FORD FIVE HUNDRED
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 11,000,000 MILES
I have 2002 ford windstar with the large v6 (vulcan) and I noticed that it has recently started pinging or knocking under acceleration. It does it when the engine is hot, not when it is cold. The problem occurs under light to moderate acceleration or just after the automatic transmission shifts. I've taken it to a diagnostic center and they have checked the EGR valve and associated systems, polled the computer for error codes (none found). I have no check engine lights or other warning lights.

Their best guesse was bad gas. I've changed brand/gas station and have run a half tank of premium through it and while the knock has diminished, it is still there. What could be causing this problem?
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Wednesday, June 8th, 2011 AT 3:24 PM

14 Replies

Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Suspect EGR the operation system may have checked out but passage ways maybe blocked with carbon. Need to remove EGR inspect and clean. EGR must operate or knock will occur
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Wednesday, June 8th, 2011 AT 4:00 PM
Tiny
HOPK6344
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  • 8 POSTS
I will double-check, but I think they took the egr valve off and checked the passage ways to make sure they were unobstructed. I remember the tech saying that could be a problem when I dropped the van off for diagnostics.
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Wednesday, June 8th, 2011 AT 4:03 PM
Tiny
HOPK6344
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I just checked with the tech - they did NOT do a physical inspection of the passages. They pulled the sensor data and the flow sensor showed full flow - indicates no obstruction.
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Wednesday, June 8th, 2011 AT 4:08 PM
Tiny
DOCFIXIT
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That just means flow of vacuum not exhaust gas into intake
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Wednesday, June 8th, 2011 AT 4:40 PM
Tiny
CJ MEDEVAC
  • MECHANIC
  • 11,004 POSTS
DOC,

COULD TIMING, OR SLOP IN THE TIMING HAVE THE SAME AFFECT?

I FEEL SURE ON THIS RIG, "ADVANCE" IS ELECTRICALLY CONTROLLED, NOT VACUUM---PRONE TO NON-WORKING MECHANICAL PARTS, LIKE IN OLDER VEHICLES.

THE MEDIC
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Wednesday, June 8th, 2011 AT 5:34 PM
Tiny
RASMATAZ
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  • 75,992 POSTS
Could also be the knock sensor not retarding the timing when engine is detonating or engine is overheating and type of fuel use
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Wednesday, June 8th, 2011 AT 5:45 PM
Tiny
DOCFIXIT
  • MECHANIC
  • 18,828 POSTS
Found Technical Service Bullitin REF> 04-19-2 that is a reflash for PCM to adjust Octane to control knock. Bummer is dealer would have to do
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Wednesday, June 8th, 2011 AT 5:45 PM
Tiny
HOPK6344
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  • 8 POSTS
Well, my mechanic flushed the fuel injectors and the combustion chamber to remove carbon, still getting the preignition. Next on the list is to do a physical inspection of the EGR ventilation passageways. Also, found out that this year of ford does not have a knock sensor. If this doesn't work, what would you recommend?
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Monday, June 13th, 2011 AT 5:51 PM
Tiny
HOPK6344
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The timing chain/belt (whatever it uses) and the sprocket was replaced 30 thousand miles ago. (About 3 years ago).
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Monday, June 13th, 2011 AT 5:53 PM
Tiny
HOPK6344
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  • 8 POSTS
Mechanic said the ventilation passages were clear, but found a problem with the EGR control solenoid. Could this be causing the problem? Also, wouldn't that cause an error code on the computer?
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Monday, June 13th, 2011 AT 9:45 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
If the engine is pinging/detonating and the EGR valve is not doing its job it will cause a high combustion temperature and NOx will sky high and cause it to ping. Don't always rely on the computer to give you something when there's a problem within the engine management system it'll be nice though if it does
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Monday, June 13th, 2011 AT 9:52 PM
Tiny
HOPK6344
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Thanks. I hope this turns out to be the problem. It's highly inconvenient buming a ride to work when you have a 45 mile commute.
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Monday, June 13th, 2011 AT 10:01 PM
Tiny
HOPK6344
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Well, replacing the EGR solenoid and cleaning the injectors/combustion chamber seemed to fix the problem. I picked the van up yesterday, and stress-tested it by accelerating up a steep hill from a dead stop. No pinging or preignition noises. It still seems odd that the solenoid would not have tripped a error code on the computer. I'll monitor it closely over the next month to make sure it's not a temporary improvement. Thanks everyone for your suggestions. I'll be using this service again!
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Tuesday, June 14th, 2011 AT 3:48 PM
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Thank you for letting us know that your problem was resolved successfully with help from our expert contributors.
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Saturday, June 25th, 2011 AT 9:30 PM

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