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MrDiag
MrDiag, ASE Certified Tech
Category: Car
Satisfied Customers: 168
Experience:  16 Years Of Automotive Repair and Management Experience.
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MULTIPLE MISS FIRE 302 304..COILS PLUGS WIRES

Resolved Question:

MULTIPLE MISS FIRE 302 304 308 JUST ONE BANK
NEW COILS PLUGS WIRES AND INJECTORS. ALL CYL. AT 100LB. COMPRESSION. VACCUM STEADY RUNS GOOD AT HIGHER RPM ALSO NEW CAM SENSOR.

ANY IDEAS ON WHERE TO GO
Submitted: 2 years ago.
Category: Car
Expert:  MrDiag replied 2 years ago.

MrDiag :

check the scan tool data when acting up and observe the vehicle speed, a common problem is a faulty speed sensor that tells the Engine Control Module (ECM) the truck is doing 180 MPH and the ECM shuts down a bank of injectors to slow the truck down.

MrDiag :

Sorry, didn't send complete message. My name is XXXXX XXXXX X am here to help. It sounds like you have covered a lot of the known problems. These engines did have an exhaust valve issue but with staedy vacuum I don't think that is your problem. So try the above.

Customer:

If it shuts down one bank how come our missfire is on only 2 4 8??

MrDiag :

I know this is pretty far out of the box but when the basics are covered we have to get creative. If the signal is intermittently off and causes a quick iteruption in injector pulse it could be hard for the ecm to catch every cyl misfire. The only other things I can think of are injector issues, or possibly O2 issue for that bank. I have seen a failing O2 cause multiple cyl misfires on one bank.

Customer:

new 02 sensor also this came in with multple codes this keeps re occuring.

MrDiag :

Is it a contant miss? Have you done injector balance test?

Customer:

has new injectors

Customer:

could a bad converter cause multiple miss fire

MrDiag :

Silly question, did it have the miss before the plugs, coils etc were replaced? Were they oem? Have you checked the cat?

Customer:

yes o2 sensor and multple miss fire on both banks

Customer:

fule pressure at 55Lb

Customer:

possible ECM??

MrDiag :

Have you treid running it with ft O2 out on that bank to see if less backpressure helps?

Customer:

yes

MrDiag :

And no change?

Customer:

correct

MrDiag :

Are there any other codes setting?

Customer:

300 missfire and 1300 302 304 308

MrDiag :

There are some of these where the MAF will cause multi misfire but usually not all on one bank.

MrDiag :

Is the O2 a universal where you have to make your own plug?

Customer:

no

Customer:

measured flow on mass air seems good

MrDiag :

Have you tried running a good top engine cleaner?

Customer:

yes twice

MrDiag :

Did you check voltage drop at injectors on that bank?

Customer:

no last thing to do. Have to pull Plentum off for that

MrDiag :

This is a tough one

Customer:

tell me your email and i will update you on what we find

MrDiag :

Did you check injector spray while replacing injectors?

Customer:

no they are all new

MrDiag :

Ok. I am going to switch this to a Q&A format and you will be able to post to it for at least 7 more days.

Customer:

Thanks for your help

Expert:  MrDiag replied 2 years ago.
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Expert:  MrDiag replied 2 years ago.

We are still able to communicate this way

 

Expert:  MrDiag replied 2 years ago.

You're welcome. Let me know what you find.

Customer: replied 2 years ago.
Converter bad on bank 2 Replaced it no codes car runs great
Expert:  MrDiag replied 2 years ago.
Glad that you found the issue. That is what I was thinking when I mentioned running it without the precat o2. They sure can be tricky sometimes. I hope my information was helpful.
MrDiag, ASE Certified Tech
Category: Car
Satisfied Customers: 168
Experience: 16 Years Of Automotive Repair and Management Experience.
MrDiag and 19 other Car Specialists are ready to help you

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