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Crank misfire?

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12 Oct 2019 16:45 #34205 by Toddf
Crank misfire? was created by Toddf
2006 2500hd lq4 gas, gets random misfires on all cylinders, no check engine light. Has all new injectors, coils, plugs, wires. Grounds cleaned, maf sensor cleaned, vac hoses checked, new knock sensors. Suspected crank sensor issues. No access to a scope

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12 Oct 2019 18:56 #34209 by Chad
Replied by Chad on topic Crank misfire?
Do you have access to Scan Data? What do your Fuel Trims look like?

"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer."

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12 Oct 2019 19:23 #34210 by Toddf
Replied by Toddf on topic Crank misfire?
Yes long term was at 9 bank 2 and 6 bank 1, thought everything was pointing towards dirty injectors, replaced them and now fuel trims are about 2 long term both banks. Forgot to mention intake gasket is also new, replaced a year ago. Misfire is mostly at idle randomly on all cylinders. Thanks for the reply

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12 Oct 2019 19:25 #34211 by Toddf
Replied by Toddf on topic Crank misfire?
Scan data I have is from a actron 9185 and torque pro, nothing fancy

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12 Oct 2019 19:52 #34213 by Toddf
Replied by Toddf on topic Crank misfire?
Fuel pressure is at 60 psi, and is only about 3 months old, Delphi unit. I also done my best at a back pressure test suspected a clogged cat on bank 2 which made some noise at times in the past, reading was between 0 and 1 but needle was erratic

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28 Oct 2019 12:29 #34611 by FrugalPrepper
Replied by FrugalPrepper on topic Crank misfire?
Well the 9185 won't do mode 6 so you won't be able to get misfire data from the computer with what you have. How do you know it's on all cylinders if there is no codes for misfires. Could it be on 2? I would start with a load balance test to see if you can isolate which one(s) are the culprit.

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29 Oct 2019 16:54 #34637 by scannerjohn
Replied by scannerjohn on topic Crank misfire?
Trims of 2 is not bad... anything over +- 10 is what you do not want.

You say you have all cylinder mis-fire but no codes. I take it you basing that on a vibrating engine.

At idle with the engine at operating temp and the 02's in closed loop what are the STFT and LTFT for B1S1 and B2S1.

Increase idle to 2500 RPM, what are the trims now.

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13 Nov 2019 05:22 #34972 by Toddf
Replied by Toddf on topic Crank misfire?
Misfire data I have is from torque pro app, misfires all cylinders mostly idle only, occasional after letting off throttle.

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13 Nov 2019 05:27 #34973 by Toddf
Replied by Toddf on topic Crank misfire?
Have been swamped with work lately appreciate response will try and check stft and Ltft at 2500 today. Again misfire data is coming from torque pro app, all cylinders not constant just random at idle. Thanks for all the help

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13 Nov 2019 05:56 #34974 by Toddf
Replied by Toddf on topic Crank misfire?
Ok it's only 12 degrees here today, at idle stft1 is -1.3, stft2 is -0.8, ltft1 8.6, ltft2 7.8. At 2500 rpm I have stft1 -3.6, stft2 -2.3, ltft1 9.4, ltft2 8.3

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