10000 miles misfire can't find the issue, checked plugs wires injectors coils compression need some help in flordia

 

Where in a Florida are you located ??…I’m in Cape Coral…easy to diagnose but you need the right equipment…if you’re near bring it by !!…could be an injector…and even with good compression it still can be a mechanical issue. Moved this thread to Tech.

 

Is the miss random or a specific cylinder? If you have the "Torque" program for your phone, you can run "Test Results" to get cylinder-specific information on misfires.

 

I'm in springhill but it's drivable and could bring it to you

 

Thats fine !!…just let me know when you want to bring it down…this weekend is fine or early next week…hurricane may be coming up this way....is your LS3 supercharged ??

 

Outstanding how about after this hurricane thing I'll make my way down 3043661974 ty

 

OK, is your LS3 supercharged ??…auto or manual ??…if you have a flashing check engine light not a good idea to drive it to much…you can “F” up your CATS !!

 

Whip the valve covers off and make sure your valve train is ok, ie: valve springs, pushrods and rockers are acting properly. OR if you have an infrared hand held thermnometer, aim it at the header or exhaust pipe exiting cylinder head.......to see which one is running cool.....to isolate a cylinder. Does the "check engine" light flash occasionally? if so, i wouldnt drive it far at all.

 

auto all stock and yes the check engine flashes

 

check all the valve train all looks good I did not use the infrared to isolate one cyclinder and light does flash

 

Great ideas !!…OP said he only “checked” plugs, wires, coils compression…one must do more than a physical inspection to nail down these misfires without changing a bunch of parts or doing “swaptronics”…I use a labscope and also do advanced testing such as in cylinder pressure analysis…you might find one in a thousand shops or dealerships that do this testing…good for finding something like a worn cam lobe or something that may not be revealed with a compression test that is good and also verifying the misfiring cylinder…sometimes a misfire can be a companion cylinder or the cylinder before or after the misfiring cylinder in the firing order.

 

I wouldn’t drive it until you come down this way !!… do you actually “feel” it running rough or the MIL just flashes ??…how about I call you ??

 

Try and get a gun laser thermometer, you can narrow down which cylinder is having the misfire. I did on mine and it turned out it was the injector. You can swap plug wire and plug with another and see if the misfire follows it, same for coil or injector. Possibly your o2 sensor, if you had hand held code reader you can see what the cel is for.

 

Take it to Autozone or another parts store and have the codes read. Then post them on here. That way you should not have to drive it very far.
More analysis has to be done after getting the codes. But it is valuable information.

 

Friend pulled codes on my car when my check engine light was on but he didn't tell me how he did it There's a procedure where he could pull his own codes on the car.

 

Below is the shop's findings after a misfire was diagnosed:



Customer Concern: CUSTOMER STATED THAT THE VEHICLE HAS A MISFIRE HE HAS REPLACED THE PLUGS AND WIRES BUT IT STILL MISFIRES .

COMPLETED

Technician Notes: Basic assessment of the engine's misfires find that while the fault code set in the engine Control Module indicate "Random Misfire" the misfires are, in point of fact, largely isolated to cylinder bank one and, furthermore, cylinders one and seven seem to be the most heavily affected. Knowing this, the technician proceeded in evaluating the operation capacity of the ignition coils and spark plugs which, as the client well knows, are operational. In spite of this, and purely due to the originality of this equipment, the technician does recommend that it be replaced. The fuel injectors, as is evidenced in the reference photos provided, were tested for both flow rate and pulse response using the bidirectional functions of the scan tool and found to equitably deliver fuel and pulse promptly and properly when commanded. Knowing the above, and having experienced the engine's general running quality, the technician elected to next assess the engine's general production of vacuum. As is demonstrable in the reference photos provided, the technician compared measurable engine vacuum with the interpretive value represent by the manifold absolute pressure sensor and finds the margin of error between mechanically measured and electronically measured to be less than three percent. As such, the technician can abandon use of the mechanical gauge and employ use of exclusively the MAP reading during the reminder of testing. In this case, measurable vacuum with the engine under any semblance of load is approximately 13 - 14 inHg which, for a large V8 engine, is abundantly low. This, in turn, implies a flaw in the engine's ability to intake fresh air or exhaust combustion gasses. Technician measured the temperatures above, at, and below, the exhaust catalysts to ensure that both flowed well. Measurements of temperature are equitable and fairly consistent with properly functioning catalysts but, purely for the sake of eliminating speculation, the technician removed the upstream oxygen sensors from both the bank one and two exhaust manifolds so that an outflow point might be created ABOVE the catalysts. With the sensors removed, measurement of engine vacuum remained largely unchanged. Unfortunately, this implies that the general diminishment of engine vacuum stems from the engine itself. At this juncture, the technician requests an additional four (4) hours of diagnostic labor for the performance of compression testing, cylinder leak down testing, measurements of valve lift, assessments of the pushrods, valve springs, rockers, and other elements of the engine's valve train. PLEASE NOTE: WHILE UNRELATED, THE TECHNICIAN FINDS IMMEDIATE NEED FOR REPLACEMENT OF THE VEHICLE TIRES. With diagnostic authorization acquired, the technician proceeded with diagnosis at the scheduled time allotted by the service staff. Given the vehicle's symptoms, and having gleaned a cursory amount of information during the performance of initial testing, the technician elects to assess the engine's base mechanical timing. With this engine's timing component service calling for upwards of ten hours of labor, direct access is simply implausible so, as an alternative method, the technician elects to gain access to the Engine Control Module so that an oscilloscope might be used to backprobe the signal return wires from the Camshaft and Crankshaft Position Sensors. This method, as opposed to affixing the oscilloscope to the circuitry nearest to the aforementioned sensors, is a simple consequence of safety and practicality: Reasonable access to the CKP requires that the starter motor be removed and the CMP is located within a few millimeters of the accessory drive belt. As is evidenced in the provided reference photos, the technician gained access to the ECM via the removal of the right front wheel and the right front wheel housing liner before removing the ECM from it's cradle for easy access. The circuits backprobed are pins 64 and 68, respectively, at ECM connector X2.

Technician Notes: With the oscilloscope affixed, the technician started the vehicle and monitored the waveforms generated. As is with all position deriving reluctors, one tooth of each of the respective reluctors associated with the CKP and CMP Sensors will be distinct and produce a distinct signal wave. Assessment of engine timing in this manner simply involves simultaneously monitoring the waveforms generated by both the CKP and CMP sensors and ensuring that these distinct waves occur in synchrony. Synchrony of the waves indicates that these distinct reluctor teeth - reluctor teeth which denote Top Dead Center of Cylinder Number One - are in the same relative positions and thereby the engine can reasonably called "in time". Evidentiary photographs make very clear that this is NOT the case with this vehicle. While it's clear to see that the distinct waves do not align, the technician's further calculations determine camshaft timing to be late by approximately 22 degrees. With this information garnered, the technician cannot simply jump to any conclusions as in rare cases certain types of electrical interference (predominantly faulty terminating resistors) can cause false positives in these tests. So, the technician then determined a method which mechanical mistiming could be validated without the complete disassembly of the engine. The method which the technician elects to use is by assessing what is referred to in industry lexicon as "split overlap" at cylinder one's top dead center. To provide some context, when a respective cylinder is at the top of it's compression stroke (speaking exclusively of four stroke engines here), and the camshaft is timed in synchrony, the intake and exhaust valve(s) associated with that cylinder should either be entirely closed or ever so slightly open (contingent upon engine design specifications) for a brief period at the point which combustion occurs and the flame front provides that cylinder's piston with turbulence. To achieve this, the technician removed all of the engine's spark plugs to allow the engine to be turned by hand more easily, installed a compression testing adapter into cylinder one, and held the end of that adapter to his ear while simultaneously rolling the engine over by hand. Once the technician could hear the cylinder generating compression, the engine was turned until precisely the point at which the generation of compression could no longer be heard. Then, using a borescope, the position of the piston was confirmed and the valvetrain assessment began. While the rocker arm associated with cylinder one's intake valve could be wiggled freely (this engine is set up for zero lash and zero preload; an interest risk by the manufacturer), the exhaust valve rocker stood rigid. As such, and using a dial indicator to provide measurement, the technician loosed the rocker while measuring exhaust valve recovery. In doing so, the technician confirmed valve recovery of 0.077 in. which, in short, is a mechanical indicator of late timing. At this juncture, the technician recommends replacement of the engine's timing components and intercessory service/reseal of all items required for access. POST REPAIR NOTES: With the engine reassembled, the technician takes immediate note that engine idle quality has greatly improved. Preliminary test drive, in spite of engine idle quality having greatly increased, resulted in the technician experiencing a persistent, single cylinder, engine misfire. Returning to the repair facility, the technician finds that the entirety of cylinder bank one is no l
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------After talking to the OP I'm going to take a ride up to his place next week weather permitting and see if I can diagnose this misfire...there are a few things I find troublesome by the shop he had brought it to:
1) even though OP replaced plugs and coil packs no secondary ignition testing was done...no mention of plug wires being resistance checked or checked with a scope.
2) low manifold vacuum of 14-15 inHg...yes, a timing issue can cause this and Tech determined that the timing was retarded by 22 degrees...if it were retarded that much the car probably wouldn't start and there would be MULTIPLE cylinders misfiring…the Tech said the chain skipped one tooth...car has a little over 10,000 miles and it is true a skipped chain will retard the timing... THE TIMING CHAIN WAS REPLACED…a cam/crank correlation was performed but NO waveform given to the owner...a timing gear with a skipped tooth will cause more than one cylinder to misfire...VERY surprised the shop uses a scope !!...a vacuum leak can also cause low manifold pressure and I don't see a screen capture of the MAP sensor voltage or pressure...a vacuum gauge showing 14 inHg was included but you have to see what the ECM is seeing...KOEO Baro should read about 29.9 inHg at sea level and MAP inHg on good running engine at idle should be roughly 10.0 inHg...29.9 minus 10.00 equals 19.9...a GOOD manifold vacuum...my LS1 screenshot below...no mention of fuel trims which would indicate a vacuum leak...engine was in open loop so fuel trims can't be observed but you can look at the O2 sensor data PIDS.
3) shop would need 4 hours to do compression, leak down testing and valve lift measurements...HUH ???...compression testing can be done either with an AMP clamp around negative battery cable and the other 2 can be done via an in cylinder pressure transducer...less than 5 minutes for "relative compression test and 15 minutes for the other 2..the hardest part is removing the spark plug and screwing in the transducer and hose...compression testing
with a gauge or relative compression with a scope is one of the FIRST things to check !!
4) even after the timing chain was replaced a misfire still observed !!
5) the MAF reading at idle is 10.46 grams/second...too high...MAF is over reporting...should be close to the liter displacement of the engine...6 to 7 grams/second would be good on a warmed up engine...dirty MAF can cause this over reporting MAF...fuel trims under load will have to be looked at...nothing about O2 sensor readings were included.

ANY IDEAS ???...thanks !!...hopefully this will be easy to diagnose !!

 

Why is the MAF 10.46 on one page and 7.03 on the other? Picture showing 7.03 has engine speed covered up. Both pictures indicate closed loop mode.


Also, high fuel trim on bank 1, both short term and long term, indicates vacuum leak. Bank 2 Fuel trims look good.
HO2S is oxygen sensor information, 4 sensors, 2 in each bank.

Bank 1 S1 show it is at least switching low. Transient nature of o2 sensor makes it impossible to see on a picture, unless pictures are taken at both switching high and switching low levels. A waveform is really needed.

Bank 1 S2 o2 sensor reading seems high. I would not expect to see them in the 900 range.

Bank 2 S1 showing high level which looks ok.
Bank 2 S2 is closer to what I would expect to see, 785.

 

LOL !!..that is my car that I was showing the correct MAP sensor values in the box...the shop is going to call me back to discuss this diagnosis !!…OP’s car was in open loop at the time !’

 

This is exactly what we did one time with my 2008 Z06 that was missing. Of course, it had an aftermarket cam, so it wasn't setting a code (misfires tuned out), but I could feel it in the throttle. It turned out to be a cracked spark plug.