EXCESSIVE backfire and weird rumbling noise

[rtrocket59]

My talon has always had back fire every now and than but recently it's been happening alot. I have 255 warlboro fuel pump, aem AFPR, PTE 880 injectors and a V3 DSMlink. This was all installed and tuned by JNZ tuning.

In between shifts from 1-3 gear I get one really loud back fire that sounds like a bomb going off. When letting off the gas in any gear I get really short quick backfires. Kind of sounds like popcorn being made .

Also when I let off the gas I hear an awful sound that i think that is coming from some kind of bearing. Its a constant rumble that doesn't go away until I get back on the accelerator. It's a lot more noticeable when I'm on the highway in 5th gear when I let off the gas.

Obviously the constant rumble is not normal, but is the backfire supposed to be so obnoxious? I feel like it can't be a tuning problem since JNZ is one of the most reputable shops around. Maybe I just need a real dyno tune but I would rather wait until I put my big turbo in and rebuilt trans.

 

[LiquidX]

Have you verified your mechanical timing and your ignition timing? With the consistence that it's occurring I would be led to believe that a valve or valves on the exhaust side are not closing fully. A compression test would help narrow down a sealing issue.

 

[rtrocket59]

Have you verified your mechanical timing and your ignition timing? With the consistence that it's occurring I would be led to believe that a valve or valves on the exhaust side are not closing fully. A compression test would help narrow down a sealing issue.

Now that you say that, I remember that it started to happen after getting my timing belt changed from a local shop (everything such as water pump, pulleys, etc were changed too). Maybe he accidentally advanced my timing too much by accident?

Would you have anything to say about the rumbling noise when i let off the gas? I feel like its coming from the trans.

 

[jayson427]

Do you have a wideband? Sounds like something is off for sure

 

[rtrocket59]

Do you have a wideband? Sounds like something is off for sure

Yes I do have a wide band. It's located on the downpipe that jnz fabricated

 

[jayson427]

Well what does the gauge read when it has bad backfires?

 

[rtrocket59]

Well what does the gauge read when it had bad backfires?

Don't have a wideband gauge yet :/

Also the left rear axle sticks out of the differential a little bit which may be part of the grinding/ rumbling noise. But I hear the sound from the front of the car and not the rear.

ran the car cold this morning and noticed that I wasn't getting back fire. As the car got warmer, it started to back fire progressively