Backfiring through exhaust when engine is warm

[Breakdown]

Cats gone. Wasn't on the truck when I bought it. I plan on placing one on it in the near future (dynomax has the y pipe and cat kit for around 200) but as of right now it's not even there

 

[Breakdown]

So the backfire through the exhaust has reared its ugly head again.. Thought I had it fixed. So heres what I have changed and fixed to date
1) IAC (new AC Delco)
2) TBS (Delphi)
3) EGR (AC Delco- tested with vacuum gauge, good indications)
4) Coolant Temp Sensor AND switch
5) Cap, Rotor, Wires, Plugs
6) Set timing with EST wire disconnected to 0 degrees (was at 4)

OK I'm at a loss here. I hooked my timing light up tonight to the coil wire and looked at the fuel spray pattern on the TBI. I couldn't see the spray/mist, but I could see where the fuel was hitting the sides of the bores on the tbi and was running down from there, didn't look like rain or drips coming from the injectors. I don't have the adapter to test my fuel pressure yet. The exhaust after it warms up does smell like unburnt fuel. Really starting to get irritated. I'm going to start calling this truck the spawn of Satan, and request the local priest come and do an exorcism on the engine.....
Somebody give me some starting points to troubleshoot from here. All the sensors I replaced ( I verified with a multi meter both before and after replacement using testing procedures I have found) were in desperate need of replacement. Ive replaced all of the hard vacuum lines and fittings, with exception of the charcoal canister vacuum line (pulled the vac fitting and put a good cap on it to
see if I had a leak, no idle change, and its not idling high)
The thing that bugs the crap out of me, is its not doing this when its cold, which is when the ECU sends more fuel to the engine to get it up to temp. Its only when its hot, and before it starts to backfire I can hear a slight change in the engine.. not a noticeable difference on the tach, but its idle changes somewhat, and it sounds a bit rougher than it does prior to it getting up to temp.

Oil pressure at idle cold- approx 45 PSI
oil pressure at idle hot- approx 18-20 psi
Hot driving- varies from 20-30 depending on RPMs.. just something Ive noticed

 

[Breakdown]

Oh and on the EGR, I have a handheld mighty-vac pump that I applied vacuum with for testing, not just a gauge.
I also tested the engines vacuum at idle- held at 22 in HG vac, with a slight vibration of the needle (not fluctuating, just vibrating about a 1/2 in +/-)

 

[Breakdown]

So I had a tbi rebuild kit from ac Delco I purchased a couple weeks ago. Went ahead and tore the tbi down tonight and gave it a proper going through. Discovered the fp regulator diaphragm wasn't ripped but looked like it had seen better days. The spring was good but there was a ton of crap inside of the housing for the spring. The tbi base gasket was sucked in a bit on one side as well and there was a small vacuum hose that goes to the charcoal canister solenoid that was pretty much destroyed as well. I took it the whole tbi apart and soaked it in a carb dunk tank for about thirty minutes to break up the sludge and debris covering it and replaced all the gaskets and o rings.
Post rebuild start and drive went smooth. She started up a lot easier (6 or 7 revolutions previously, sometimes more. Now hit the key for a second and bam she's purring) acceleration by the butt dump seemed significantly better as well.
The small fuel injector screens were straight black. Might have been causing fuel spray issues but we will see tomorrow on the stop and go traffic from the ship on the way home. One more thing down about a million to go.
I got a new truck one part at a time haha

 

[vic_v8]

sounds like you got it, nice

 

[Breakdown]

Here's to hoping but every time I think I've got it narrowed down it pops back up again. I got bored today and used a polishing kit I had to clean the headlights since they were so yellow I could barely see this morning. I know it's not engine related but I through some pics of what I did the last week up

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[Breakdown]

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Although something I did notice..... clean the engine last week and now this shows up....looks like oil spray from the filler cap..... either my engine oil drains are clogged or I've got a. BLow by problem... new pcv and all my vacuum ports are pulling great vacuum now

 

[kennythewelder]

I got bored today and used a polishing kit I had to clean the headlights since they were so yellow I could barely see this morning.

Sense you have already cleaned you headlight, and if you have not do so already, You should do the 4 high headlight mod, but also add an extra relay for just the low beams. This makes a huge difference. When I did my 4 high mod and saw how much brighter the lights were on high, I could not believe the difference, but when on low beams, they were still dim. So I figured I would try another relay on just the low beams. I cut the OE + wire for the lows next to the battery, and use this for my switch wire to activate the relay. Then I ran a AWG # 10 wire from the battery to the relay input and back to where I cut the wire on the headlight side. Now my lights are supplied straight off of the battery from a larger wire. This makes a huge difference in brightness. I did not replace any wire to the lights, I just tapped in a larger wire straight off of the battery. The only other thing I had to do was to remove the fuse for the DRLs. This was enough power (the DRLs) to activate the relay.

 

[Breakdown]

Nope that didn't fix it. So it started doing it again today. Got it home put it in park and held the throttle down at about 2500 rpm on the tach would run for about thirty or forty second then just turn itself off. No sputtering just bam engine turns off. What the hell.... this is the first time ive tried this and it doesn't make much sense.

 

[Breakdown]

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So pulled the ignition control module. Looked to be the oem gym module but there was hardly no thermal paste underneath it. Taking it over to the zone to hook up to there icm tester. That yellow looking powder isn't corrosion from what I can tell looks like dust and pollen...