ok i have a 96 z28 camaro with the LT1 in it... when i bought the cats had been taken off already this mite be the problem...i dont know that why im here posting....so i trick the back 02 sensors...so there not throwing a code for them anymore.....but now it throwing the p400 code this is EGR..... i have put brfand new EGR and vaccum sylenoid and reset the comp and in 5 to 10 miles it came back on ....this is really aggrivating i have check everything to see if there are any clogs there is none.....please help........thank again,......

 

http://www.obd-codes.com/p0400

you live in an emissions state? if you don't, just pull the EGR valve off and block on the holes. I blocked off the EGR ports and pulled the solenoid and get P0400 and P0403
i think re-burning exhaust gases is retarded and does more harm then good.

 

Not an unusual problem with a low backpressure exhaust, as one without cats would be.

Check the vacuum lines as well.... one of them may be cracked.

The purpose is not to "re-burn" exhaust gas. The exhaust gas is recirculated under limited operating conditions, to cool the combustion chamber when driving under conditions that might cause high combustion chamber temps. An example would be when lugging the engine at low RPM in the wrong gear. It will help prevent detonation (knock). Doesn't flow at idle, doesn't flow at WOT, doesn't flow above 3,500 RPM, so there is no negative impact on performance.

 

If the EGR doesnt flow above 3.5k rpm then how does it prevent knock? Since when is knock an issue (or an occurence) at RPM 3500 and under? Not doubting ur knowledge, just trying to understand what you mean as i was under impression knock is a phenomenon that happens primarily at high RPM/WOT (under stock PCM settings and no outside tuning)

 

This

 

Lugging the engine at low RPM in the wrong gear builds huge combustion chamber pressures, which increase the heat/temperature. Very common to get knock at low RPM under those conditions. Run an M6 at 1,500 RPM in 6th gear, and floor it, and you'll get a lot of knock - or in this case, a lot of knock retard.

 

The cooling effects would obviously aid in fighting against knock but it didnt make sense to me how car would get knock at such low rpm (but i was thinking in terms of an AT tranny) but as i relate it to a manual being lugged from high gear i now get it. So for the A4 the EGR is even less of a factor and could be blocked off/removed without any real consequence. Cool, thanks for clearin that up.