Home » Video » ...

Chevrolet trailblazer random misfire Videos

Diagnosing random misfire without check engine light or codes

2001 Chevy S10 with hesitation and stumbling, occasional misfire but owner brought in after clearing check engine light and erasing codes and freeze-frame.

User Comments

ILTSYC commented on 26 Nov 2015

Id like to have seen how you hooked everything up to the oxygen sensors or did you get that strait out of the OBD2 port?

ILTSYC commented on 27 Nov 2015

+Schrodingers Box I'm wanting a good scan tool and scope. A used snapon Modis with an integrated 4 channel Scope looks appealing.I like the idea of a PC based scan tool and scope because if the lap top breaks I can fix it or replace it and simply reload the software as opposed to sending the Snap on in and getting the ole - you might as well buy another used unit for the cost to repair this guy routine.

Schrodingers Box commented on 27 Nov 2015

I just used a basic scantool is all

jon white commented on 06 Mar 2015

i have a 2003 Chevy s 10 pick up random misfire at idel at times rough idel at times not all the time once a week or so started off as cylinder 4 misfire replaced cap roter wires coil pack fuel pump spider injector got rid of cylinder 4 misfire now get the random misfire replaced cap roter disturber crank shaft sense o2 senser Catalytic Converter mass airflow had large e vap leak replaced Vapor Canister Purge Valve Vapor Canister Vent Solenoid replaced lines to fix it by replacing the filler neck smoked engine no signs of leaks fuel psi 55 no other codes but random misfire take it for a sticker but your vehicle was rejected because it was "Not Ready. Catalyst Efficiency Monitor Not Ready EVAP Monitor Not Ready drove it for 7 - 8 days still not ready

Schrodingers Box commented on 06 Mar 2015

When GM cars have a random misfire detected, they go into "OL3" mode which will basically prevent completion of the emissions monitor testing. You have no choice but to fix the random misfire.

WD Hewson commented on 23 Mar 2014

More great stuff. You're a rigorous thinker. All information must "jive". Regarding exhaust leaks, my expectation is that exhaust back pressure just blows out rather than sucks in air to cause a lean low voltage O2 sensor. Or is there an aspiration effect that overcomes this back pressure? It's probably a bit complicated by pulsed exhaust flow at low engine power too. Thanks again.

DE “AutoBravado” Nichols commented on 12 Sep 2014

Go to his discussion page after clicking on his channel. There is a big post covering O2's actually detecting hydrocarbons, not O2. Gojudude started the thread.The reason it was taught that it detects O2 is that it'd make it easier for mechanics to understand.Occasionally knowing that it's seeing hydrocarbons makes situations clearer. Before reading the statement I was already suspecting it was true since it didn't logically fit with all situations.I believe in an exhaust leak above an o2, 2 things will happen. Some hydrocarbons will escape causing the engine to look like it's running leaner than it is. At higher flow, the venturi effect of the exhaust going over the leak will pull outside air in. The system can show it's "leaner" just because it's cooler.When I had an exhaust leak in front of my catalytic converter and I had a high load or high RPM it'd make air burp into the system.My post catalytic converter would show rich at these times. Why? The exhaust was being cooled and the cat wasn't hot enough to burn the hydrocarbons. Usually when driving slower, the rear o2 would show leaner, showing a good burning of the hydrocarbons. Realize, that when a cat isn't working the lean/rich will happen much more rapidly showing that it's bad. Whether it's more rich or lean doesn't matter as much as if it's mostly steady. At that point the ECU will think it's healthy cat.All this comes together for me, because the exhaust leak would frequently spike rich on the rear o2, and that switching told the computer I had a bad cat, even though it was new. The ECU was fooled, but I'm no longer fooled by the difference. I can tell when watching live scan data.WD? Thank you for the comment, it got me really thinking. :)

Chevy Vortec 5.7 Problem Tahoe 1996 RPM's

96 Chevy, Tahoe, Miss, 5.7, Motor, Problem, 350, RPM's, Gas, Air, Let me know what you guys think.

User Comments

Septic Trucker commented on 03 Sep 2015

Had and still am having a problem with my 1999 suburban. Grinded when i tried to start so i pulled my coil wire and cranked and it didnt grind. replaced my Crank sensor and now no spark

em3rge1 commented on 24 Dec 2015

check your starter mine was cracked did the same thing

Diagnosing a misfiring chevy 350 part 1

The Cheap rehab '79 Chevy truck is running pretty good, but still has a nagging misfire. A recent compression test and plug analysis reveals that the bottom end ...

User Comments

Jim Rowlings commented on 09 Sep 2014

does it have heat riser valves

WhoSaidTyler commented on 10 Sep 2014

Used to but not any more.

moparmania74 commented on 08 Sep 2014

I thought you said before how you had a low compression cylinder? which seems about right. looks like a ring is not seating well and when it warms up it expands and seats better. you also might have a vaccum leak somewhere. I never trust bolts in vacuum hoses. ive never had good luck doing that.

moparmania74 commented on 08 Sep 2014

if you did the intake gasket on this. maybe you should retorque the bolts. spray some brake clean around. see what you find...