1999 Mazda B3000 Engine Ping or Knock under load

Tiny
AIRDALE1956
  • MEMBER
  • 1999 MAZDA B3000
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 209,474 MILES
My problem is engine knock under load. I run 87 octane gas. If I run E85 gas no knock but fuel mileage sucks. I tried 89 octane gas with no success, I have been able to run 2/3 87 & 1/3 E85 with no knocking. The in line fuel filter has been replaced. The ECM is just been replaced and is up to date. MAF is clean air filter is clean. No diagnostic codes. Spark plugs have all been gapped properly.040" I am the 2nd owner of the truck, and I don't know if the fuel injectors have ever been cleaned or replaced. My question is was this engine designed to run on 87 octane gas? I have replaced the Ign. Coil pack in TSB 20031231 Is there any other way to resolve this problem.
Tuesday, April 6th, 2010 AT 7:23 AM

7 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Try cleaning out the EGR valve and see what happens
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Tuesday, April 6th, 2010 AT 11:53 AM
Tiny
AIRDALE1956
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  • 4 POSTS
I will try your suggestion, Can you give a reason as to why you are recommending this approach?

Thanks David
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Tuesday, April 6th, 2010 AT 5:47 PM
Tiny
RASMATAZ
  • MECHANIC
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If the EGR valve don't open it wil raise the oxides of nitrogen and increase the engine combustion temperature this will cause the engine to detonate/ping-like a bunch of marbles thrown into an empty tin can.
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Wednesday, April 7th, 2010 AT 12:59 PM
Tiny
AIRDALE1956
  • MEMBER
  • 4 POSTS
Well I removed the EGR valve, checked the intake manifold port for being clogged, it's not. Checked the EGR Valve for proper operation it seams to work fine. I put evey thing back together. I started the engine to check for vacuum on the EGR, by placing my finger over the hose. I detected no vacuum at idle, then gradually increased RPM to 3500 where the engine started cutout like a rev limiter. During this time I detected no vacuum on the hose during an increase or decrease in RPM. So I think I have two problems 1. Being I have no vacuum at the EGR valve at any time, and 2. The engine is missing and is cannot go beyond 3500 RPM while sitting the driveway in park.
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Tuesday, April 13th, 2010 AT 6:43 AM
Tiny
RASMATAZ
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Check the vacuum switching solenoid and vacuum source on the intake manifold
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Thursday, April 15th, 2010 AT 10:35 AM
Tiny
AIRDALE1956
  • MEMBER
  • 4 POSTS
Well I have vacuum at the solenoid, so I know the intake port & line is good. I need to know under what conditions the solenoid is suppose to open? Engine temp, load, what causes the vacuum switching solenoid to operate?

Thanks David
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Saturday, April 17th, 2010 AT 7:45 AM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
The computer could be using the throttle position sensor or aiflow meter signals as a load to activate the VSS as rpm increases. Other causes for pinging is too advance ignition timing-
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Saturday, April 17th, 2010 AT 8:02 AM

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