I have the problem stated above however the backfire is out the intake on startup and sometime when the car warms up at idle it pops really loud. It was 95 degrees here today and Im suspecting that to be the cause. But the car also has a difficult time starting now. There are no engine codes and no knock. The tps voltage is .67 with the key on. The car also hesitates a little when the backfire is through the exhaust.

 

Need a lot of details. Most important - what did you do to the car just before the problem started?

Rich

 

I adjusted the tps switch by reaming out the fixed placement holes to achieve .67 volts at idle. my car idles at only 800 warmed up and 500 or so in gear.

 

nobody?

 

When you say it idles at 500rpm "in gear", we have to assume that its an A4. Stock idle for an A4 is 550rpm in gear and 650rpm in neutral. Its sort of hard to know what your current engine consists of, since your signature describes it as "383 underway".... is it still "stockish" or has the 383 build been completed? Is the programming stock, or "tuned"?

Are you saying it ran fine, until you drilled out the TPS sensor so you could adjust it to 0.67 volts? What was it reading before you adjusted it? Were you adjusting it in some sort of attempt to change the idle?

A backfire out the intake generally means the fuel ignited in a cylinder before the intake valve was fully closed. Could be a problem with ignition timing - cross-firing on the plug wires, for example - or it could be a problem with a valve hanging open. Any chance this happened with the Opti changes?

 

As Fred said, backfiring is usually a timing issue. Did you do anything recently that could have changed the timing? Crossed plug wires will do it, for sure. I have done that more than once. I can't see how the TPS would cause it.

Rich