Backfiring through exhaust when engine is warm

[Breakdown]

ok gents first post of the head bashing saga. My truck is a 95 c1500 extended cab vin k with the 4l60e automatic. Here's my issue.
When it's cold the truck runs like a beast. After it warms up and has been ran for a bit if I get on the throttle hard (getting up the on ramp for instance) BANG goes the exhaust and immediate loss of power. If I walk the throttle I can get to bout half throttle before it pops. I've checked the timing with the est wire disconnected (was 4 degrees before tdc) reset it to factory recommended tdc. New cap and rotor, new egr valve and idle air control, and new throttle pos sensor ( all three were shot verified using multimeter... in a tech for the navy I can diagnose bad sensors) put a new cts in when I replaced the thermostat (shot... actually in two different pieces when I popped the housing) the truck does not have a cat installed (previous owner must have straight piped it)
This problem is killing me though. Everything I've replaced has made improvements but haven't solved my course issue. It runs like a ***** ape when cold and to a point when it's up to temp the. Bang it starts acting dumb. Any ideas?

 

[RichLo]

Have you replaces the coolant temp sensor yet?

Backfire through exhaust is generally a running rich problem. a bad signal from the coolant temp sensor would cause your problems.

 

[Breakdown]

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Replaced the coolant temp sensor and the pigtail. Soldered and heat shrinked the new pigtail into place (cause crimps and vampires splices look like butt lol) think I figured it out tonight. I yanked the plugs and wires tonight (had a new set I picked up the other day just haven't had the chance to replace yet) and found some problems. One of the wires looked like it had been on the truck from the production line, the plugs were way overdue for replacement ( my gauge wasn't big enough to get a damned measurement) and the idiot who had this truck before me didn't know how to run a set of wires... these wires were twisted around each other only one or two actually were in the looms and basically they were a cluster of crud. Put the new wires and plugs in and seems like it MIGHT have cured the problem... this truck is a basket case though. Instead of spending the thirty bucks and twenty minutes to replace the heater core he just bypassed it. Bad rgr valve... bypassed. Temp sender for the guage? Must have been leaking as the wire was there and the end of the sender but a pipe plug threaded in its place. Had a bad throttle positioning sensor to boot.


Come on people if you stay on top of maintenance it doesn't take much time and effort to keep something running correctly. I love this truck but I absolutely hate the billy bob mentality the previous owners had. Fix it right the first time!!!

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[Breakdown]

Just a couple pics to show. The headliner and overhead console I did and wired up myself this weekend. I need a ac delete plate for the console though but it came out pretty decent. It's running pretty decent now that I got a lot of the top end stuff squared away. Next up is the o2 sensor fuel filter and new valve stem seals (smokes a bit when you start it up and when you take off from red lights.... I call it spraying for mosquitos Roflnao) and it's due for rear axle bearings. Pretty easy jobs and not to expensive!

 

[kennythewelder]

How is your 02 sensor? that controls fuel trim, just a thought.

 

[Breakdown]

I'm not sure how bad the o2 is... I can take a guess though seeing how bad the rest of the maintenance was and say it's probably the original Delphi part. Question- what brand of o2 sensors do you recommend? I ran Bosch on mopars and on my VW's but I've heard that gm and Bosch don't like each other much...

 

[90halfton]

Could very likely be an exhaust leak. Possibly exhaust manifold or nearby. Throws the 02 sensor off when hot as well. Easy thing to check for anyways. Happened on an old dually we had. Was a cracked manifold.

 

[kennythewelder]

Could very likely be an exhaust leak. Possibly exhaust manifold or nearby. Throws the 02 sensor off when hot as well. Easy thing to check for anyways. Happened on an old dually we had. Was a cracked manifold.

True. As for 02 sensors, well I haven't had any issues with any I have used. Bosh or other brand, but sense you just need 1 may as well get AC Delco, or Delphi, or whatever the OE brand you can get is. Sorry, I know this sounds kind of lame, but I haven't changed mine in a while.

 

[Breakdown]

Honestly wouldn't surprise me. Drive the truck to work this morning and the problem didn't pop up any more. I'll check the exhaust out this weekend when I put a new o2 in it.

 

[vic_v8]

What about a cat that's clogging up? I've seen them clog up to the point where they would get hot and shoot a section of "honeycomb" out the tail pipe.