Engine suddenly starts to ping (detonate)

[pontiacgp]

simply put egr's are shut at idle and work on vacuum top let exhaust gases back into the intake when above idle. The gases from it cool the combustion chamber allowing more advanced timing.

 

[gthmcty1]

simply put egr's are shut at idle and work on vacuum top let exhaust gases back into the intake when above idle. The gases from it cool the combustion chamber allowing more advanced timing.

Is there a way to bypass to see if the is the issue (EGR)

 

[pontiacgp]

I don't think it's the EGR...if the EGR was stuck open it would cause a rough idle but it would not cause pinging...and reversed if it was stuck closed it could cause pinging but not a rough idle. Have you checked your timing with a gun yet?

 

[gthmcty1]

I don't think it's the EGR...if the EGR was stuck open it would cause a rough idle but it would not cause pinging...and reversed if it was stuck closed it could cause pinging but not a rough idle. Have you checked your timing with a gun yet?

Checked timing and it is solid at 15 degrees

 

[gthmcty1]

BAD GAS????

 

[Bonnewagon]

The test for EGR is to put full vacuum to it and see if the car stalls at idle. You can also feel the underside with a finger and see if full vacuum opens it up. A backpressure activated type only works when enough exhaust backpressure is present to close an internal valve that lets the EGR operate, that kind can only be tested by replacing with a known good valve. A stuck valve that is slightly open at idle, would cause rough idle, yet not opening enough would cause detonation at part throttle. But then again, so would a big vacuum leak.

 

[pontiacgp]

good point about being partially open...

 

[gthmcty1]

Guys is it possible that a bad knock sensor could be causing the detonation but the only thing about that is the service engine light doesn't come on on the dash

 

[TexasT]

I don't think it's the EGR...if the EGR was stuck open it would cause a rough idle but it would not cause pinging...and reversed if it was stuck closed it could cause pinging but not a rough idle. Have you checked your timing with a gun yet?

Checked timing and it is solid at 15 degrees

Is there a vacuum leak? Is the vacuum advance on he distributor working? Does the timing advance as you rev the engine?

 

[gthmcty1]

I don't think it's the EGR...if the EGR was stuck open it would cause a rough idle but it would not cause pinging...and reversed if it was stuck closed it could cause pinging but not a rough idle. Have you checked your timing with a gun yet?

Checked timing and it is solid at 15 degrees

Is there a vacuum leak? Is the vacuum advance on he distributor working? Does the timing advance as you rev the engine?

My distributor does not have a vacuum advance on it....(Is that normal?) checked for vacuum leak and no leak