I need major help from the board!!! I am hoping Traxion or Grumpy can quickly get me back on track, although I am sure many of you have lots of experience as well.

My problem is programming a 355 TPI, with World Sportsman II heads and a ZZ-9 cam with 1-3/4 headers. I recently replaced my old injectors with SVO 24# injectors (stock program). I have read over Traxion's article on programming (excellent articles). I think my problem is with my BLM's. I am getting alot of backfire as the car idles and even with a little pressure on the accelerator at around 1500-2000 RPM. This is making it exceedingly difficult to make adjustments to the VE curve.

To start I set the TPS to .54 volts with the fuel pressure set to 40 psi. I am not sure if that is a correct way to start off. So I was getting BLM readings of 128 at idle and then the count went to 154. I was actually glad to see this, since I would alter the VE table with the Prominator that I have installed. However after I stepped the RPM's up by 200 the BLM count was at about 124 to 127. These readings seemed alright. Certainly not out enough to make my car idle and backfire like it was.

I am hoping someone can shed light on something that I am overlooking so I can get to programming. I am at the end of my ideas as to what might be the problem.....

 

By backfire, do you mean popping through the intake or through the exhaust?

Are you sure you have the timing right? It should be set at 6* BTDC. I've only tuned a stock car, but this sounds like a mechanical problem to me if it's popping through the intake. Too much advance?

I would verify that the timing is right before you try to tune it out with programming.

 

the timing is set at 6 degrees. I think the popping is coming out of the exhaust which makes me think it is running rich. I have an AFPR but not too sure if 40 psi would be right with the 24# SVo injectors that I have. Am I correct in assuming that if I am running rich or lean then the BLM numbers should be something drastically different than 128?? Also what are your thoughts on the TPS setting. I figure that should also not have a huge impact on the problems that I am experiencing...

 

Is the system going into closed loop at idle/light loads, if not then you might need a heated o2 sensor since you mentioned that you are running headers. If the system is not going into closed loop then the BLM will be locked at 128 if the ecm has been disconnected from its power source. Does it smell rich? If possible post a log file that we can look at.

 

Hi Eric,

Yes the ecm is going into closed loop. I thought I should invest in a heated o2 sensor (becuase mine old one was probably origional). I have replaced it and I am getting signals from it. I think it smells rich. It is leaving black spots on the garage floor. As for posting a log file, I am not sure how to do that. I am kind of new to this tuning thing (but am very eager to get going).