Exhaust popping/backfire on decel

[steel_3d]

I get a slight popping and sometimes a decent backfire when I decel in slow city driving.

Is this most likely due to ignition or cam timing?

I believe my ignition timing is correct. I got a 6-bolt in a 97, so all I could do was get the timing light to match the logger reading range, and that was between 10-15 deg btdc at idle.

My cam timing is a little more funky. I have FFWD 272 regrinds, and I had to advance the exhaust 5 degrees and retard the intake 5 degrees on Skunk2 gears to get it to idle smoothly (and almost pass smog). I believe I wasn't getting these pops and backfires before the cam timing change. I adjusted the ignition timing at the same time though, that's why I'm a bit confused.

Anyone have specific answers as to which way I should tweak things? I tried retarding and advancing my timing in the 0-3000rpm low load range by 4 degrees, and neither made a difference. It's possible that the advanced exhaust cam timing is doing it...

 

[pneumo]

Check and adjust your TPS. Normally the ecu shuts off fuel when coasting in gear. The 2G uses the TPS sensor to know when the throttle is closed. If the adjustment is off the ecu will think the throttle is still open and continue adding fuel.

 

[scottsee]

Agreed. Sounds like the TPS isn't alligned properly throwing off the ISC and not allowing coasting fuel cut to occur. Can you log ISC, IPW or IDC to verify? Or it could be you have a leaky injector..

 

[steel_3d]

I'll double check the tps as soon as I have time, but It's reading .7v at idle, I was thinking that's about right. But you guys might be right cause my idc's stay at 3% when decelerating. Should be cut to 0 on 2g's?

 

[sd_ff22]

damn I need to get a logger cable. I have the stock t25 but I have replaced my tps and I get that little popping under deceleration too. should be just an adjustment then for me?

 

[steel_3d]

It definitely needs to be adjusted when it's replaced. All the manuals will have the procedure. You can also look at the bottom of this page for quick reference: http://www.roadraceengineering.com/2gtbswap.htm

 

[scottsee]

TPS should be set to .63v for Idle, Coasting fuel cut will turn off your injectors completly showing IPW=0ms and IDC=0%. Loosen your throttle cable tension on the back of your intake manifold, and see if the TPSvolts drop. If not, I'd re-align the TPS.

If you had Dsmlink this would be so much easyier.