[FIXED] Dead Misfire

Hello Guys. I’m in need of Waveform and help Cam and crank Correlation on 96 Dodge Ram 1500 3.9lts distributor ignition system. Symptoms are cyl. 4,5,6 are dead as per cylinder drop down test. So three cylinders are not contributing. First we dis relatively compression are good, spark and Ignition are good. Customer have replaced the distributor rotor, cap, wires and plugs. Exhaust is good and no restriction. We checked those wires making sure they are on the right cylinders and they are all good. Injectors are good and we even checked flow test and they are all relatively the same. Now we are down to Input side of it. We have taken the Cam and Crank Signals and we will compare that with the Good Known Waveform. Pls i need ur help with the waveform and with some ideas for diagnostic. The distributor have been adjusted to 0 or near 0 degree according to Procedure and problem continues to exist. Pls need ur help guys. Need more diagnostic ideas. On the trouble shooter they talk about Distributor not in 0 degree at idle and shaft itself has a excessively play but not the case on this one. We checked it and they are all
Good and we turned the distributor 0 degree at idle using Data PIDS on Verus. Pls i need Help. Thanks

update: here is a known good from diag.net to compare to. Your cam/crank are spot on.

Is the misfire there at higher RPMs too?
Two checks I would start with at this point.
1. Head gasket issue (use a block tester)
2. Possible intake gasket leak (why I asked about higher rpm)

Higher RPM has a misfire Too. It does not seem to change at idle and higher RPM. At Some Point of Diagnostic I have thought about Internal Vacuum Leak as this is a V-Type Engine, but it Does not Match the Vacuum Leak sypmtoms as Dead Misfire is Constant at idle and Higher RPM. We are gonna try to do Leak Down test to those affected cylinders 4,5,6. Put each cylinder to Top Dead Centre on compression stroke and leak down test it and see what happens. it is easy to get to those Cylinders anyway. I will keep u guys posted. Thanks for ur response guys

Thanks. My Waveform is dead on. Thanks and I appreciate

Do you have injector control and flow on them 3 cylinders?? Possibly a bad distributor cap to like on the gm’s that cross fire and cause misfires.

Also what does map sensor voltage and vacuum reading look like? Is it nice and steady or oscillating like a vacuum gauge would with a mechanical issue

Cap And Rotors are New and it was a tune up that customer did prior to bringing it in to the shop. we already through those Checked. Thanks

Injector control and flow test are all good. We did go through those checks as well. Thank You. it MISFIRE AT IDLE AND higher RPM. and No change at all

Vacuum Reading at Idle with dead misfire is bouncing between 13-14 Steady

We did Checked those Affected Cylinders for Leak down and each losing about 20PSi of pressure as well as the rest of the Cylinders in the Piston Rings as it is shown in the Dipstick tube and none through throttle plate and Exhaust Tail Pipe. My question now is, is it possible that those affected cylinders are not getting enough Air or not getting Air At all and How is that Possible? I have Exhausted all my Diagnostic ideas on this one.

ADD On: No visible sign of leaking in the Cooing system during leak down test on those affected cylinders as well as known contributing cylinders

What’s the oxygen sensors look like? Readings? Maybe see if the exhaust is plugged up free flowing on both sides

And just because it’s a new cap and rotor doesn’t mean it’s good.

Hi Guys. Just Keep Everybody Posted. Running Compression Test is the answer to this One. During Cranking Compression Test, it shows Relative Compression test is relatively the same as well as Compression gauge shows 150-155 PSI compression pressure in every cylinder. However, We did a Running compression Test and Number 6 Cylinder has 0 PSI compare to the rest of the Cylinders so We decided to take the valve Cover off and see it Physically what is going on in there. We found Exhaust Broken Spring. so The Running Compression Test is the Winner. WE would have never be able to catch the 0 Compression pressure if we would have relied only on Cranking Compression test or Based upon what the actual Compression gauge says Because really Number 6 cylinder shows the same reading as the rest of the cylinders. Thank You Guys so much for all ur inputs. I'm please with ur responses. we definitely learned a lot from this Truck. It almost get our butts kicked. Thank u guys so much. Peace

did you have a relative compression waveform? im sure it would have looked different for that cylinder because the exhaust couldnt escape the cylinder.

I wish I could have saved it but I did not as they were relatively he same and I did not think I saw the red Flag during the test. But anyway, thank you guys so much. I appreciate all your inputs. May GOD keeps us safe in this Difficult time. God Bless You All