1995 k1500, 5.7/350. Backfires through intake

[RhettR7707]

1995 k1500, 5.7/350, long tube headers, true duals straight piped with resonators, bypassed intake silencer and added salad bowl intake spacer. When running k&n air filter, seems to be getting too much air and backfires through the intake. Is there any way without having to tune ecu, to get the truck to run more fuel or at least balance itself while having the maximum amount of air possible. Typically happens around 2500+ rpms. Maybe a O2 sensor signal modifier? Could it possibly be a timing issue? Thanks.

 

[RhettR7707]

Replaced O2 sensor, MAP sensor, EGR valve, plugs, wires, distributer cap, TPS, IACV, knock sensor, and others within 20,000 miles from now. Also have checked with break clean for vacume leaks, couldn't find any. Are there any common hidden ones I should know about? Thought that may be helpful. Has 136,000 miles currently.

 

[PlayingWithTBI]

Is there any way without having to tune ecu, to get the truck to run more fuel or at least balance itself while having the maximum amount of air possible.

What's your fuel pressure when it happens? A lot of times, when you add go fast parts, you can increase your fuel pressure. Maybe 14 - 20 PSI depending. You can get maybe up to 15 PSI with a stock spring or go to an 18 LB one for higher pressures. Of course, you'll want an AFPR and gauge setup to fine tune it.

 

[RhettR7707]

What's your fuel pressure when it happens? A lot of times, when you add go fast parts, you can increase your fuel pressure. Maybe 14 - 20 PSI depending. You can get maybe up to 15 PSI with a stock spring or go to an 18 LB one for higher pressures. Of course, you'll want an AFPR and gauge setup to fine tune it.

I'm not sure about the fuel pressure. Is there a port to check it on the 95 350s? From what I understand, the only way to really check it is to tap into the main line somewhere. Is there a way to adjust the fuel pressure regulator on a tbi? Forgot to mention that it was in fact tbi.

 

[PlayingWithTBI]

I'm not sure about the fuel pressure. Is there a port to check it on the 95 350s?

Not really, you can "borrow" one from your local parts house which goes in place of, or next to the fuel filter. You can also install your own with this adapter and a gauge or schraeder valve.
www.marine-performance-parts.com/gmtbiperformance.aspx

CFM Technologies

CFM Technologies sells and manufacturers Magazine + TV Featured performance parts for GM TBI , Throttle Body Injection, along with custom carburetor spacers and the famous HVH Super Sucker Carb Spacers.

marine-performance-parts.com

Is there a way to adjust the fuel pressure regulator on a tbi?

To a certain point but not by much. An Adjustable Fuel Pressure regulator is better. It goes in place of the OE spring and housing. Here's an example...

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Here's what it looks like when installed and running a 28 LB spring.

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Forgot to mention that it was in fact tbi.

Yeah, I figured that when you posted for a 1995

 

[RhettR7707]

Not really, you can "borrow" one from your local parts house which goes in place of, or next to the fuel filter. You can also install your own with this adapter and a gauge or schraeder valve.
www.marine-performance-parts.com/gmtbiperformance.aspx

CFM Technologies

CFM Technologies sells and manufacturers Magazine + TV Featured performance parts for GM TBI , Throttle Body Injection, along with custom carburetor spacers and the famous HVH Super Sucker Carb Spacers.

marine-performance-parts.com

To a certain point but not by much. An Adjustable Fuel Pressure regulator is better. It goes in place of the OE spring and housing. Here's an example...

You must be registered for see images attach

Here's what it looks like when installed and running a 28 LB spring.

You must be registered for see images attach

Yeah, I figured that when you posted for a 1995

I really appreciate all of the information. Where could I get an adjustable fuel pressure regulator at? I searched for a bit but I couldn't seem to find one anywhere. Also, I'm not familiar with the spring your referring to. How do those work? Is it the one in the fuel pressure regulator? Thanks again

 

[DerekTheGreat]

"Long tube headers.. TBI.."

Where at in the header is the O2 sensor? Did you install a heated unit? I've heard that with non-cast iron manifolds the non-heated O2 sensors don't get hot enough. Would be worth getting a scanner and observing what the O2 sensor is doing when it backfires.

 

[PlayingWithTBI]

Where could I get an adjustable fuel pressure regulator at? I searched for a bit but I couldn't seem to find one anywhere. Also, I'm not familiar with the spring your referring to. How do those work? Is it the one in the fuel pressure regulator?

A quick Google search came up with this one. The one I have was from RV Morse who passed a few years ago. Note the spring in the picture. That's what you change/adjust to obtain desired FP.
www.ebay.com/itm/191259567037?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=191259567037&targetid=4580359299605901&device=c&mktype=&googleloc=&poi=&campaignid=437225724&mkgroupid=1228154759183859&rlsatarget=pla-4580359299605901&abcId=9300907&merchantid=51291&msclkid=cccf140614bf11947646722c6280c111

 

[RhettR7707]

"Long tube headers.. TBI.."

Where at in the header is the O2 sensor? Did you install a heated unit? I've heard that with non-cast iron manifolds the non-heated O2 sensors don't get hot enough. Would be worth getting a scanner and observing what the O2 sensor is doing when it backfires.

The O2 sensor is actually installed on the exaust pipe, right past the header. I'm not sure if it was a heated unit or not, I cannot recall. I did buy mine from autozone, but I can't remember which one it was.

 

[DerekTheGreat]

Oh yeah, you'll want to rectify that with a heated unit. If all you see is one wire going to it, it's a non-heated type. Either way, you'll definitely want to get a scanner and see what it's doing.

I've heard O2 sensor cross counts should be 20 or greater. The unit in my truck reports 6 at best. As a result, I sometimes get the error code for "Lean limit reached."