Exhaust back pressure test

By using a cylinder leak down tester u determine we're its leaking but this idea of using of it to check back pressure I think its cheep without a transducer or without removing the 02s all u do is take the spark plug off and set it when the exhaust Valve opens add air to determine if its plugged real easy I think its great idea and fast .tell me what u think.

I will move this thread into the diagnostic techniques section.
If I get problems removing an O2 sensor I usuall drill and tap a convient place on the down pipe for an M6 dia brass hose connector and plug it with an M6 set screw when I am finished.

A few pit falls on your idea first of all a cylinder leak down tester works by passing compressed air through a restrictor usually about 1mm in diameter so a very low volume flow rate air is passing into the cylinder so unless the exhaust system was 100% blocked with zero leaks not even a pin hole no back pressure would show up,

Another issue is even on a 4 cylinder because of valve overlap there is only a few 10s of degrees of crankshaft rotation around 90 BTDC on the exhaust stroke where only one exhaust valve is open.

What might work is doing it in reverse by connecting a high volume low pressure air source to the exhaust tail pipe.

M6 hose connector

Good morning, i have had a problem Xtrail 57 plate,M9R engine with an Air leak in the induction system,Customer complaint goes into limp,reduced power, confirm fault,intial daignosis smoke tested intake system, found leak on seam of intercooler,sourced new intercooler not genuine,have to remove bumper assembly to fit,reason for intercooler split was damage caused by broken support bracket rubbing through aluminium intercooler,
smoke test no leaks,road test after clearing faults,still in limp mode-great,fault codes for turbo boost sensor circuit and turbo boost control circuit,check components, find tbpsensor out of spec 6.0kohms,check against known good 1.6kohms,check wiring connectors at pcm,corrosion present on pins into pcm.
Marvellous,clean with electrical cleaner, blow out.Fit new tbpressure sensor. Clear faults,road test,still in limp,now fault codes for mass air flow sensor and turbo boost solenoid,and dpf and heater plug module,hmm maybe bad ecm?check mass air flow at connector in air box plugged in- pin 1 blank,pin2 battery supply,pin3earth reads 8.5volts,pin4 raeds9.5volts,pin 5 6.4volts, pin 6 8.4 volts,unplugged all pins read correct voltages,start car runs fine air mass unplugged,road test better but not correct,still in limp,read fault codes-codes for mass air flow and air temp sensor,built into air mass.
Road test no mil on-ok road test,breaks down lots of black smoke,stops, me with no phone,,,,, we recover now non start, cranks tries to go but no.
What to do to progress?-fault codes for air mass and turbo control solenoid circuit,also code for dpf,just like the end fell off egr and blocked air inlet,remove turbo boost sensor fit 1st look into intake manifold,pressure pulls seen on scope,put 1st look into exhaust pipe no pulses seen on scope,ok remove o2 sensor by turbo,cranks and runs, conclusion blocked exhaust,engine cant breath out, drill in front of dpf 7psi seen with o2 out,drill after dpf 0psi seen, blocked dpf,
Where would you take the daignosis from here??

Have u checked the waste gate to see if it's sticking maybe it's over boosting and going to limp mode or it's stuck open not making enough boost check the vacuum lines that go to the boost control solenoid

Just to say no fault found with the wastegate assemby,vacuum lines have been smoked and the vacuum supply is 20inches @ the supply port to the solenoid,its a normally open solenoid which allows vacuum to hold the wastegate closed,when over boost is detected it removes the vacuum allowing the wastegate to open,there is a pulsed ground signal present at the solenoid from the ecm @ the solenoid,the wastegate actuator has full movement and does not stick,I suspect either a ecm control problem with the boost solenoid or a faulty air mass meter giving a bad input to the ecm, Oneof the biggest problems i have is information for the ecm pin outs as the info on virus is in numbers and the ecm pins on car are in letters and dont match up,and autodata say the pin outs in numbers to, interesting problem don:t you think ....

That's confusing good luck

By adding high volume low pressure with a regulator can tell u Wich cat is plugged just by removing the 02s but the whole idea was not to move the o2 but there is no other way .

Best way isto drill exhaust and measure gas flow,best with a gauge in various locations throughout exhaust system,as per videos of pauls for back pressure testing.

U right

Have u tryed unplugging the solenoid or taking out the pressure line off the waste gat see what happens

Noting happens if the solenoid is unplugged,the vacuum just flows through to the wastegate,unplugging the waste gate hose just stops vacuum to the wastegate,

so black smoke indicating running rich condition or its burning oil on the turbo shaft through the seal, this is a volumetric efficiency engine because u said it was a maf not a map what is the lembda showing wot and what is the maf showing on live data

I would focus on that AFR sensor maybe its reporting wrong info and the computer adding all this gas but not enough air try seeing if that sensor its working

And on the turbo engines to actually find the leak u would use a boost leak tester because the leak won't show itself until they are in boost but hopefully that helps