bogging??

the best thing to do next would be a leak down test correct? compression test came back perfect
You got it. Compression seems good, so it doesn't seem like it's a ring issue. Leakdown will tell you the condition of the valves. Are you noticing any oil residue buildup in the tailpipes? 3 quarts is quite a bit to burn (assuming it was filled with the correct amount of oil at the last oil change) and I would expect to see some evidence of it.
 
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You got it. Compression seems good, so it doesn't seem like it's a ring issue. Leakdown will tell you the condition of the valves. Are you noticing any oil residue buildup in the tailpipes? 3 quarts is quite a bit to burn (assuming it was filled with the correct amount of oil at the last oil change) and I would expect to see some evidence of it.

would oil residue be considered a black kinda dust/coating? because if so then yes. could my backfire be contributing to this?
 
would oil residue be considered a black kinda dust/coating? because if so then yes. could my backfire be contributing to this?
Yep, it's usually a thicker, black coating on the inside of the exhaust. If you wipe some of it off, it feels a little gritty and oily between the fingers. Normal carbon buildup doesn't feel oily, just gritty. It takes awhile to build up, so a backfire usually wouldn't cause the build up (unless you're backfiring all the time). Did you mean misfire btw? I hadn't seen anything where you said it was backfiring.
 
Yep, it's usually a thicker, black coating on the inside of the exhaust. If you wipe some of it off, it feels a little gritty and oily between the fingers. Normal carbon buildup doesn't feel oily, just gritty. It takes awhile to build up, so a backfire usually wouldn't cause the build up (unless you're backfiring all the time). Did you mean misfire btw? I hadn't seen anything where you said it was backfiring.

usually backfires when I downshift most likely due to tune and and no cats. I'll double check the coating when I get out of work and see if its oily.
 
Hi again, Yikes! That’s certainly a lot of Oil loss, prior to this, when was the last time you had done an Oil/Filter Change, did you do it..or...an Oil Change Station (establishment of exact Oil loss on a timescale, AND how many miles, is an indicator to help to pinpoint the issue). Did you use (or request) a different type and/or Oil viscosity, what Filter were you running-? Do you have Catch Cans that collect excess Oil in the PCV System between Valve Cover to Intake lines?
Common Reasons Engine Oil can impact or cause a CPS CEL..
1) The Oil Control Valve (OCV) connected to the camshafts may be stuck or have clogged oil passages.
2) The oil is too thick, causing the passages to become clogged. This can be from the wrong oil or lack of oil changes.
3) The camshaft phaser is or intermittently becomes stuck in the advanced position.
Oil burning evident on cold startup is generally indicative of worn Valve Seals, your Motor isn’t old- does it have very high Mileage? Or the last Owner didn’t do the scheduled interval Oil changes..
This Black media in your Exhaust ; you’ll know it’s Oil- laden by rubbing a sample between your Fingers, it’ll be sticky.. O2 Sensors are prone to
functional Inability when Oil saturated, if you’re truly losing undiluted Oil through the Exhaust, I’d expect the 02’s to read, incorrectly. CEL.
Pending Codes May take (7) ‘out of parameter’ CPU logs to become a HARD Code, only then throwing a CEL. Other, real issue causing Sensor related anomalies may simply not produce a CEL, some cause instantaneous CEL’s- Typically, if the one Sensor causes a Vehicle to revert into ‘Limp mode’.
Scantool troubleshooting works best by analyzing Vehicle Data while running & viewing PID’s, grabbing and viewing values over time, observing each Sensors in live operation & verifying they compensate, easy to spot one ‘Pegged’ or out of parameter Sensor, far before a CEL. Drivecycle/Freezeframe are useful in many Scantools, one to seek out
is the free ‘Top reported fixes’ Database of Millions of Shops, giving Top reported fixes of any/all DTC’s & CEL’s your Car Throws, Actron coins this as “Code connect”, and is always present, very accurate.
There is a Test similar to the OBD1 EEC-IV’s Cylinder balance Test for OBD-2’s, same principle, Car diagnoses by looking at load percentages per Cylinder, Cars CPU needs to have a Device request to initiate (being why I’m speaking of Scantools). What Model do you have?
Do you recall the Backfire issue occurring since you reTuned or directly after the Exhaust was modified, or did it just slowly evolve over time, and it’s Exhaust only, never through the Intake?
It’s typically ok if your Cylinders are within 5-10% of each other, I doubt Rings- but You should redo the Compression Test (just one Cylinder will
Do, initially. Test one Cylinder with (5) Rotations, note PSI. Then Squirt about a Tablespoon of Oil into the Cylinder, Run the Compression Test again and if you have a *significant improvement, E.G; 150 jumps to 180 PSI, then you may have Ring issues.
If it does improves, it May be a/some/all Cylinders are glazed, causing Rings to no longer be “Seated”, # 1 cause is from very Rich/improper Air/Fuel mixtures, #2 leaky Injector(s), #3 intermittent or weak Spark. Gas-washing the Piston/Ring lubricating Oil down & out of the Cylinders into the Crankcase- and can wipe out Main/Rod Bearings if let go too long, in which case you may be able to smell Fuel in your Oil- or oil level RISES , and being Diluted- loses Viscosity, in later stages, gets into the Chambers easily and Burns off with little or no Smoke...
As you just changed your Oil & Filter, old Oil is not around to test... Note, Rings can be re-Seated if necessary once issue is resolved.
Have you checked the PCV System? Improper Crankcase evac. from normal or excessive Blowby can cause rear main Seal leaks, pressure forces normal Piston/Ring Cylinder Oil up into the Combustion chamber, right by the Oil Control Ring & Compression Rings causing excessive Oil burning, and other anomalies.
When you pulled your Plugs in the beginning of this, prior to the CPS Sensor CEL, did you note any single Plugs that differentiated from the rest (Black or Oil Saturated)? You didn’t mention it, but just checking..
And otherwise, post Oil Change- the Cars Running Strong, Starts well, run better than before the issue started- or the same?
Certainly, the leakdown Test is a given. I’m most interested in Both how long in time & Miles between knowing your Crankcase was full with Oil, to where the level became so low. And, your PCV System condition.
Take care! John